WO2012013940A2 - Catalyseurs pour la génération d'hydrogène et piles à combustible - Google Patents

Catalyseurs pour la génération d'hydrogène et piles à combustible Download PDF

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WO2012013940A2
WO2012013940A2 PCT/GB2011/001156 GB2011001156W WO2012013940A2 WO 2012013940 A2 WO2012013940 A2 WO 2012013940A2 GB 2011001156 W GB2011001156 W GB 2011001156W WO 2012013940 A2 WO2012013940 A2 WO 2012013940A2
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metal
nanoparticles
catalyst
process according
core
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WO2012013940A3 (fr
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Shik Chi Edman Tsang
Karaked Tedsree
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Isis Innovation Limited
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    • H—ELECTRICITY
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    • H01M8/06—Combination of fuel cells with means for production of reactants or for treatment of residues
    • H01M8/0606—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants
    • H01M8/0612—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants from carbon-containing material
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    • C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
    • C01B3/22—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by decomposition of gaseous or liquid organic compounds
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    • C01B2203/0266—Processes for making hydrogen or synthesis gas containing a decomposition step
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    • C01B2203/10—Catalysts for performing the hydrogen forming reactions
    • C01B2203/1041—Composition of the catalyst
    • C01B2203/1076—Copper or zinc-based catalysts
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • the invention relates to a process for producing hydrogen, catalysts for producing hydrogen or for use in fuel cells, processes for producing the catalysts, and uses of the catalysts in fuel cell applications.
  • Hydrogen has attracted increasing attention as an important alternative secondary energy resource particularly when combined with fuel-cell technology, which may play a very significant role in power generation in the future.
  • the storage and transfer of hydrogen are also problematic because of its low volumetric energy density.
  • most of the tested hydrogen storage materials such as metal hydrides, carbon materials, porous metal-organic frameworks, and ammonia can only store low amounts and high temperatures are required to release the stored hydrogen.
  • most H 2 is produced industrially by reforming hydrocarbons or alcohols and by the water-gas-shift (WGS) reaction at high temperatures.
  • WGS water-gas-shift
  • ultra-pure hydrogen gas is required by the fuel cells.
  • the gas stream usually has to be free from CO gas ( ⁇ 10ppm) otherwise the catalytic performance of the fuel cell is severely hampered.
  • the cumbersome multistage water gas shift (WGS) and CO cleanup processes as well as the slow response at start-up for hydrogen production preclude the technology from many uses.
  • Formic acid which is nontoxic and a liquid at room temperature, with a density of 1.22 g. mL '3 , has been widely used as a hydrogen source for transfer hydrogenation.
  • DFAFC direct formic acid fuel cells
  • EMF electromotive force
  • DFAFC technology has shown electro- oxidation activity far superior to DMFC and in some cases performances approach those of H 2 -PEM fuel cells.
  • a direct formic acid fuel cell is a preferred power source for portable devices such as cellular phones, personal digital assistants (PDAs), laptop computers, etc.
  • Formic acid was first reported to be an excellent fuel for polymer electrolyte membrane fuel cells in 2002, and since then formic acid fuel cells have become an active area of research.
  • the electrochemical reactions in a direct formic acid fuel cell (DFAFC) are shown below:
  • the present inventors have provided heterogeneous nanocatalysts which are active for the decomposition of simple hydrogen-containing molecules in the liquid phase, including formic acid.
  • the catalysts can be used to generate hydrogen from such molecules at room temperature. They can also catalyse the electro-oxidation of such compounds in fuel cells, forming protons instead of H 2 .
  • the present invention provides a process for producing 3 ⁇ 4 from a compound of formula (I), (II), (III) or (IV):
  • R 1 is H or unsubstituted or substituted Ci.io alkyl
  • R 2 is unsubstituted or substituted Ci. 10 alkyl
  • R 3 is H or unsubstituted or substituted CHO alkyl
  • R 4 is H, unsubstituted or substituted C M0 alkyl, or C(0)NR 5 R 6 ;
  • R 5 and R 6 which are the same or different, are independently selected from H and unsubstituted or substituted C] -10 alkyl;
  • polymetallic nanoparticles each of which comprises a first metal and a second metal, which first metal is selected from a Group 9, Group 10, Group 11 or Group 12 d-block metal, and which second metal is other than said first metal, wherein the polymetallic nanoparticles comprise a core which comprises said second metal and a shell surrounding said core, which shell comprises said first metal; or
  • nanoparticles which comprise a metal selected from palladium, rhodium, ruthenium, iridium, copper and silver, and which have a mean particle size of less than or equal to 50 nm;
  • the catalyst comprises (a) said polymetallic nanoparticles.
  • the invention provides a catalyst for the production of hydrogen from a compound of formula (I), (II), (III) or (IV) as defined above, or for the electro- oxidation of a said compound of formula (I), (II), (III) or (IV),
  • catalyst comprises polymetallic nanoparticles, which polymetallic nanoparticles comprise a core and a shell surrounding the core; wherein the shell comprises a first metal which is palladium, and the core comprises a second metal, wherein the second metal is other than palladium, platinum, gold, iron, cobalt, nickel, titanium, tungsten, tantalum, vanadium and niobium.
  • the invention provides a process for producing a catalyst for the production of hydrogen from a compound of formula (I), (II), (III) or (IV) as defined above, or for the electro-oxidation of a said compound of formula (I), (II), (III) or (IV), which catalyst comprises polymetallic nanoparticles, which polymetallic nanoparticles comprise a core and a shell surrounding the core, wherein the shell comprises a first metal which is palladium, and wherein the core comprises a second metal, wherein the second metal is other than palladium, platinum and gold;
  • the invention provides a catalyst which is obtainable by the process of the invention for producing a catalyst for the production of hydrogen from a compound of formula (I), (II), (III) or (IV) or for the electro-oxidation of a said compound of formula (I), (II), (III) or (IV).
  • the invention provides the use of a catalyst of the invention as defined above for the electro-oxidation of a compound of formula (I), (II), (III) or (IV):
  • R 1 is H or unsubstituted or substituted CI.JO alkyl
  • R 2 is unsubstituted or substituted Cj.io alkyl
  • R 3 is H or unsubstituted or substituted CMO alkyl
  • R 4 is H, unsubstituted or substituted d.i 0 alkyl, or C(0)NR 5 R 6 ;
  • R 5 and R 6 which are the same or different, are independently selected from H and unsubstituted or substituted CMO alkyl.
  • the invention provides the use of a catalyst of the invention as defined above for the electro-oxidation of formic acid.
  • the invention provides the use of a catalyst of the invention as defined above in a fuel cell.
  • the fuel cell comprises a compound of formula (I), (II), (III) or (IV) as defined above.
  • the invention provides the use of a catalyst of the invention as defined above for the electro-oxidation of a compound of formula (I), (II), (HI) or (IV) in a fuel cell:
  • R 1 is H or unsubstituted or substituted Ci-io alkyl
  • R 2 is unsubstituted or substituted Ci. 10 alkyl
  • R 3 is H or unsubstituted or substituted Ci-io alkyl
  • R 4 is H, unsubstituted or substituted C M0 alkyl, or C(0)NR 5 R 6 ;
  • R s and R 6 which are the same or different, are independently selected from H and unsubstituted or substituted Ci-io alkyl.
  • the invention provides the use of a catalyst of the invention as defined above for the electro-oxidation of formic acid in a direct formic acid fuel cell.
  • the invention provides an electrode suitable for use in a fuel cell, which electrode comprises a conducting substrate and a catalyst of the invention as defined above.
  • the fuel cell comprises a compound of formula (I), (II), (III) or (IV) as defined above. More typically, the fuel cell is a direct formic acid fuel cell.
  • the invention provides a fuel cell which comprises: a catalyst of the invention as defined above or an electrode of the invention as defined above.
  • the fuel cell further comprises a compound of formula (I), (II), (III) or (IV) as defined above. More typically, the fuel cell is a direct formic acid fuel cell.
  • the fuel cell typically further comprises a compound of formula (I) which is formic acid.
  • the invention provides a process for the electro-oxidation of a compound of formula (I), (II), (III) or (IV) as defined above; which process comprises contacting a liquid phase which comprises said compound of formula (I), (II), (III) or (TV) with a catalyst of the invention as defined above in the presence of an electrode.
  • the invention provides a process for the electro-oxidation of a compound of formula (I), (II), (HI) or (IV) as defined above; which process comprises contacting a liquid phase which comprises said compound of formula (I), (II), (III) or (IV) with an electrode, which electrode comprises a catalyst of the invention as defined above.
  • the electrode comprises a conducting substrate and a catalyst of the invention as defined above.
  • Fig. 1 shows TEM images of polymer stabilised Pd nanoparticles a) PVP (particle size 4.5 ⁇ 0.6 nm) b) 80% hydrolysed PVA (particle size 7.0 ⁇ 0.8 nm) c) HB-PEI (particle size 9.0 ⁇ 1.0 nm).
  • Fig. 2 shows TEM images of PVP-stabilised Ru nanoparticles having particle sizes a) 1.8 nm, and b) 2.3nm.
  • Fig. 3 shows TEM images of PVP-stabilised Ru nanoparticles having particle sizes c) 2.7 nm d) 3.2 nm.
  • Fig. 4 shows TEM images of PVP-Pd nanoparticles synthesised by stepwise growth having particle sizes a) 2.3 nm b) 3.5 nm c) 5.2 nm
  • Fig. 5 shows TEM images of PVP-Pt nanoparticles having particle sizes a) 3.2 nm b) 3.8 nm c) 5.2 nm d) 6.0 nm.
  • Fig. 6 shows TEM images of PVP-Rh nanoparticles having particle sizes a) 2.0 nm b) 5.1 nm c) 10.0 nm
  • Fig. 7 shows TEM images of PVP-Ag nanoparticles having particle sizes a) 20.3 nm b) 30.2 nm c) 50.3 nm.
  • Fig. 8 shows TEM images of Au nanoparticles having particle sizes a) 10.0 nm b)
  • Fig. 9 shows TEM images of bimetallic nanoparticles prepared from co-reduction of mixed metal salts: a) Pt-Pd (particle size 10.0 ⁇ 1.8 nm) b) Ag-Pd (particle size 20.5 ⁇ 3.5 nm) and c) Au-Pd (particle size 10.0 ⁇ 0.8 nm).
  • Fig. 10 shows TEM images of bimetallic nanoparticles prepared by successive reduction a) Pt-Pd (particle size 10.0 nm ⁇ 1.8) b) Ag-Pd (particle size 18.5 ⁇ 2.1 nm) c) Ag- Pd (particle size 30.5 ⁇ 7.2 nm).
  • Fig. 11 shows TEM images of bimetallic nanoparticles prepared by successive reduction with hydrogen sacrificial protective strategy a) 1 : 1 mole ratio of Ru-Pd (particle size 3.2+0.4 nm) b) 1 : 1 mole ratio of Rh-Pd (particle size 2.8 ⁇ 0.5nm).
  • Fig. 12 shows UV-Vis spectra of Ag, Pd and Ag@Pd nanoparticle at different molar ratios
  • Fig. 13 shows UV-Vis spectra of Au and Au@Pd nanoparticles (particle size 10.0 ⁇ 0.8nm) prepared from co-reduction of mixed metal ions
  • Fig. 14 shows TEM images of 20% Pd/C a) 2.3 nm b) 4.5 nm
  • Fig. 15 shows TEM images of nanoparticles after heating at 300°C under N 2 for 0.5 hr a) Pd/C (particle size 2.7+ 0.3 nm ) b) Pt@Pd/C (particle size 42.1+4.0 nm) c)
  • Fig. 16 shows the correlation between chemical shift and mole fraction of Pd shell on Ag@Pd nanoparticles.
  • Fig. 17 shows cyclic voltammograms (anodic scan) of formic acid electro-oxidation on Ag@Pd catalyst.
  • Fig. 18 shows mass activity (at 0.2 V) of Ag@Pd catalysts containing different mole ratios of core and shell metals for formic acid electro-oxidation.
  • Fig. 19 shows specific activity (at 0.2V) of Ag@Pd catalysts containing different mole ratios of core and shell metals for formic acid electro-oxidation.
  • Fig. 20 shows electrocatalytic surface area of Ag@Pd with different mole fractions of Pd overlay er.
  • Fig. 21 shows the correlation between % surface expansion and nanocatalysts containing various mole ratios of Pd-shell on Ag-core.
  • Fig. 22(a) shows the relationship between the 13 C chemical shifts of adsorbed bridging formates on Ag@Pd, Rh@Pd, Au@Pd, Ru@Pd and Pt@Pd bimetallics and the work functions of Ag, Rh, Au, Ru, Pd and Pt; the work functions of the fee (111) plane are used for Ag, Rh, Au, Pd and Pt; for Ru, the hep (001) plane was used, having the same surface features.
  • Fig. 22(b) shows the correlation between chemical shift and specific activity (at 0.2V) of both carbon supported monometallic and core-shell bimetallic catalysts for formic acid electro-oxidation.
  • Fig. 23(a) (left) is a plot of the rates of formic acid decomposition over different metal colloids (4 x 10 '5 mole in lOmL) in water vs. d-band center.
  • Fig. 23(b) shows the correlation between the formic acid decomposition rate with the initial rate of C0 2 formation over different sizes of gold nanoparticles.
  • Fig. 24(a) shows the relationship between rate of formic acid decomposition over Ag@Pd, Rh@Pd, Au@Pd, Ru@Pd and Pt@Pd bimetallics and the work functions of Ag, Rh, Au, Ru, Pd and Pt.
  • the work functions of Ag, Rh, Au, Ru, Pd and Pt from fee (111) fee planes were used, while the work function of hep (001) hep plane was used for Ru (having the same surface feature as the (111) fee plane in the other metals).
  • Fig. 24(b) shows the correlation between the 13 C chemical shift of adsorbed formate and rate of formic acid decomposition over monometallic and core-shell bimetallic nanoparticles.
  • Fig. 25(a) (left) is a plot of chemical shift values of adsorbed bridging formate over Ag@Pd at different molar ratios.
  • Fig. 25(b) (right) is a plot of rates of formic acid decomposition over Ag@Pd at different molar ratios.
  • Fig. 26 shows the volume (mL) of gas liberation over time (mins) from unstirred reactor containing lOmL of aqueous formic acid (containing 0.5M, 1M, 2M and 4M of aqueous formic acid respectively) when in contact with 4 x 10 "5 mole of 1.1 Ag@Pd catalyst.
  • Ci- 10 alkyl group is an unsubstituted or substituted, straight or branched chain saturated hydrocarbon radical. It may for example be methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl or decyl. Typically, it is C 1-6 alkyl, for example methyl, ethyl, propyl, butyl, pentyl or hexyl, or C alky], for example methyl, ethyl, i-propyl, n-propyl, t-butyl, s-butyl, i-butyl or n-butyl. When an alkyl group is substituted it typically bears one or more substituents selected from unsubstituted Ci.6 alkyl, substituted or
  • substituted alkyl groups include haloalkyl, hydroxyalkyl, aminoalkyl, alkoxyalkyl and alkaryl groups.
  • alkaryl as used herein, pertains to a CM O alkyl group in which at least one hydrogen atom has been replaced with an aryl group.
  • a substituted C 1-2 o alkyl group carries 1, 2, 3 or 4 substituents, for instance, 1 , 2 or 3 substituents, or more typically 1 or 2 substituents.
  • An aryl group is a substituted or unsubstituted, monocyclic or bicyclic aromatic group which typically contains from 6 to 14 carbon atoms, preferably from 6 to 10 carbon atoms in the ring portion. Examples include phenyl, naphthyl, indenyl and indanyl groups. An aryl group is unsubstituted or substituted.
  • substituents selected from unsubstituted d-6 alkyl, unsubstit
  • R is an acyl substituent, for example, a substituted or unsubstituted C O alkyl group or a substituted or unsubstituted aryl group.
  • R is an acyloxy substituent, for example, substituted or unsubstituted CMO alkyl group or a substituted or unsubstituted aryl group, typically a Ci -6 alkyl group.
  • amino represents a group of formula -NH 2 .
  • C O alkylamino represents a group of formula -NHR ' wherein R ' is a CMO alkyl group, preferably a Ci-6 alkyl group, as defined previously.
  • di(Ci-io)alkylamino represents a group of formula -NR ' R " wherein R' and R" are the same or different and represent C O alkyl groups, preferably Ci. 6 alkyl groups, as defined previously.
  • arylamino represents a group of formula -NHR' wherein R ' is an aryl group, preferably a phenyl group, as defined previously.
  • diary lamino represents a group of formula -NR'R" wherein R' and R" are the same or different and represent aryl groups, preferably phenyl groups, as defined previously.
  • arylalkylamino represents a group of formula -NR'R" wherein R' is a C O alkyl group, preferably a C 1-6 alkyl group, and R" is an aryl group, preferably a phenyl group.
  • a halo group is chlorine, fluorine, bromine or iodine (a chloro group, a fluoro group, a bromo group or an iodo group). It is typically chlorine, fluorine or bromine.
  • Ci-io alkylthio group is a said Ci -10 alkyl group, preferably a C 1-6 alkyl group, attached to a thio group.
  • An arylthio group is an aryl group, preferably a phenyl group, attached to a thio group.
  • a CMO alkoxy group is a said substituted or unsubstituted CMO alkyl group attached to an oxygen atom.
  • a Ci -6 alkoxy group is a said substituted or unsubstituted Ci-6 alkyl group attached to an oxygen atom.
  • a CM alkoxy group is a substituted or unsubstituted C alkyl group attached to an oxygen atom. Said Ci- 2 o > Ci -6 and C alkyl groups are optionally interrupted as defined herein.
  • CM alkoxy groups include, -OMe (methoxy), -OEt (ethoxy), -O(nPr) (n-propoxy), -O(iPr) (isopropoxy), -O(nBu) (n-butoxy), -O(sBu) (sec-butoxy), -O(iBu) (isobutoxy), and -O(tBu) (tert-butoxy).
  • Ci -20 alkoxy groups are -O(Adamantyl), -0-CH 2 -Adamantyl and -O- CH 2 -CH 2 -Adamantyl.
  • An aryloxy group is a substituted or unsubstituted aryl group, as defined herein, attached to an oxygen atom.
  • An example of an aryloxy group is -OPh (phenoxy).
  • a reference to carboxylic acid or carboxyl group (-COOH) also includes the anionic (carboxylate) form (-COO " ), a salt or solvate thereof, as well as conventional protected forms.
  • a reference to an amino group includes the protonated form a salt or solvate of the amino group, for example, a hydrochloride salt, as well as conventional protected forms of an amino group.
  • a reference to a hydroxyl group also includes the anionic form (- 0 ' ), a salt or solvate thereof, as well as conventional protected forms.
  • a reference to a particular compound also includes ionic, salt, solvated and protected forms.
  • nanoparticle means a microscopic particle whose size is measured in nanometres (nm).
  • a nanoparticle has a particle size of from 0.5 to 1000 nm, from 1 nm to 1000 nm, or for instance from 0.5 nm to 800 nm or from 0.5 nm to 600 nm.
  • a nanoparticle has a particle size of from 0.5 nm to 400 nm, or, for instance, from 0.5 nm to 200 nm, or from 1 nm to 200 nm.
  • a nanoparticle may be crystalline or amorphous.
  • the nonpassivated silicon nanoparticles referred to herein are typically crystalline.
  • a nanoparticle may be spherical or non-spherical. Non-spherical nanoparticles may for instance be plate-shaped, needle-shaped or tubular.
  • particle size as used herein means the diameter of the particle if the particle is spherical or, if the particle is non-spherical, the volume-based particle size.
  • the volume-based particle size is the diameter of the sphere that has the same volume as the non-spherical particle in question.
  • d-block metal means a metal of the d-block of the periodic table. As the skilled person will understand, this includes metals from Groups 3 to 12 of the periodic table, including metals from Group 3, namely, Sc, Y, Lu and Lr; metals from Group 4, namely Ti, Zr, Hf and Rf; metals from Groups 5 to 7; metals from Group 8, namely Fe, Ru, Os and Hs; metals from Group 9, namely Co, Rh, Ir and Mt; metals from Group 10, including Ni, Pd and Pt; metals from Group 1 1, including Cu, Ag and Au; and metals from Group 12, including Zn, Cd and Hg.
  • metals from Groups 3 to 12 of the periodic table including metals from Group 3, namely, Sc, Y, Lu and Lr; metals from Group 4, namely Ti, Zr, Hf and Rf; metals from Groups 5 to 7; metals from Group 8, namely Fe, Ru, Os and Hs; metals from Group 9, namely Co, Rh, I
  • a Group 8 d-block metal means a metal from Group 8 of the periodic table, in the d-block.
  • the Group 8 d-block metal is usually Fe, Ru or Os.
  • a Group 9 d-block metal means a metal from Group 9 of the periodic table, in the d-block.
  • the Group 9 d-block metal is usually Co, Rh or Ir.
  • a Group 10 d-block metal means a metal from Group 10 of the periodic table, in the d-block.
  • the Group 10 d-block metal is usually Ni, Pd or Pt.
  • a Group 11 d-block metal means a metal from Group 11 of the periodic table, in the d-block.
  • the Group 11 d-block metal is usually Cu, Ag or Au.
  • a Group 12 d-block metal means a metal from Group 12 of the periodic table, in the d-block.
  • the Group 12 d-block metal is usually Zn, Cd or Hg.
  • a Group 1 metal means a metal from Group 1 of the periodic table, i.e. an alkali metal. Typically, it is Li, Na, K, Rb or Cs.
  • a Group 2 metal means a metal from Group 2 of the periodic table, i.e. an alkaline earth metal. Typically, it is Be, Mg, Ca, Sr or Ba.
  • the invention provides a process for producing 3 ⁇ 4 from a compound of formula (I), (II), (III) or (IV): R'COOH (I)
  • R 1 is H or unsubstituted or substituted CMO alkyl
  • R 2 is unsubstituted or substituted CMO alkyl
  • R 3 is H or unsubstituted or substituted CMO alkyl
  • R 4 is H, unsubstituted or substituted CMO alkyl, or C(0)NR 5 R 6 ;
  • R 5 and R 6 which are the same or different, are independently selected from H and unsubstituted or substituted C j . ⁇ o alkyl ;
  • polymetallic nanoparticles each of which comprises a first metal and a second metal, which first metal is selected from a Group 9, Group 10, Group 1 1 or Group 12 d-block metal, and which second metal is other than said first metal, wherein the polymetallic nanoparticles comprise a core which comprises said second metal and a shell surrounding said core, which shell comprises said first metal; or
  • nanoparticles which comprise a metal selected from palladium, rhodium, ruthenium, iridium, copper and silver, and which have a mean particle size of less than or equal to 50 nm;
  • the catalyst comprises (a) said polymetallic nanoparticles.
  • the catalyst comprises (a) said polymetallic nanoparticles.
  • the catalyst comprises (a) said polymetallic nanoparticles.
  • H 2 is usually produced in the gaseous state.
  • the process of the invention for producing H 2 is typically a process for producing hydrogen gas.
  • the compound of formula (I), (II), (III) or (IV) is adsorbed on the catalyst surface. Hydrogen atoms are then cleaved from the adsorbed molecules, C-H bond cleavage generally being the rate-determining step. The adsorbed hydrogen atoms then recombine to form gaseous hydrogen. (When the reaction is performed in the presence of an electrode, e.g. a fuel cell electrode, the adsorbed hydrogen is instead converted into protons at the anode.)
  • H 2 is produced from a compound of formula (I), (II), (III) or (IV) as defined above.
  • the catalysts used in the process of the present invention catalyse the dehydrogenation reaction rather than the dehydration reaction, and as a result the product gases produced in the process of the present invention typically contain no more than 10 ppm CO.
  • the product gas mixture usually comprises H 2 , C0 2 , and no more than 10 ppm CO.
  • the product gas mixture comprises less than 10 ppm CO.
  • R 1 in the compound of formula (I) is H or unsubstituted or substituted CMO alkyl, more typically H or unsubstituted or substituted Ci- 6 alkyl. More typically, R 1 is H or unsubstituted or substituted C alkyl. In one embodiment, when R 1 is a CMO alkyl group it is unsubstituted. Thus, R 1 in the compound of formula (I) may be unsubstituted C O alkyl, or for instance unsubstituted d-6 alkyl, or unsubstituted C alkyl.
  • the compound of formula (I) may for instance be propanoic acid or acetic acid. Usually, R 1 in the compound of formula (I) is H, and the compound of formula (I) is formic acid.
  • R in the compound of formula (II) is CMO alkyl, which C O alkyl is either unsubstituted or substituted with one, two or three hydroxyl groups.
  • R in the compound of formula (II) may be unsubstituted CMO alkyl, or for instance unsubstituted C 1-6 alkyl, or unsubstituted CM alkyl.
  • the compound of formula (II) may for instance be methanol, ethanol or propanol.
  • R in the compound of formula (II) may be CMO ⁇ kyl substituted with one, two or three hydroxyl groups, or for instance Ci -6 alkyl substituted with one, two or three hydroxyl groups.
  • R in the compound of formula (II) is C 1-6 alkyl substituted with one or two hydroxyl groups, or for instance C alkyl substituted with one or two hydroxyl groups.
  • the compound of formula (II) may be ethylene glycol or glycerol.
  • the compound of formula (II) is methanol, ethanol or ethylene glycol.
  • R 3 in the compound of formula (III) is H or unsubstituted or substituted C 1-6 alkyl; or for instance H or unsubstituted or substituted CM alkyl. Typically, it is H or unsubstituted C 1-6 alkyl. More typically it is H or unsubstituted C alkyl.
  • the compound of formula (III) may for instance be formaldehyde, acetaldehyde or propanal
  • R 4 in the compound of formula (IV) is H, unsubstituted or substituted C ⁇ .e alkyl, or C(0)NR 5 R 6 ; or for instance H, unsubstituted or substituted C alkyl, or
  • C(0)NR 5 R 6 More typically, it is H, unsubstituted C !-6 alkyl or C(0)NR 5 R 6 . Even more typically, it is H, unsubstituted CM alkyl or C(0)NR 5 R 6 . Usually, R 4 is H or C(0)NR 5 R 6 .
  • R s and R 6 which are the same or different, are independently selected from H and unsubstituted or substituted alkyl.
  • R 5 and R 6 which are the same or different, are independently selected from H and unsubstituted or substituted C 1-6 alkyl. More typically, R 5 and R 6 , which are the same or different, are independently selected from H and unsubstituted or substituted C alkyl.
  • the alkyl group Q.io alkyl, C ⁇ . 6 alkyl or C alkyl
  • R 5 and R 6 are both H.
  • R 4 is H or C(0)NH 2 and the compound of formula (IV) is ammonia or urea. It may be ammonia, for instance.
  • the compound is a compound of formula (I) as defined above. In another embodiment, it is a compound of formula (II) as defined above. In another embodiment, it is a compound of formula (III) as defined above. In another embodiment, it is a compound of formula (IV) as defined above.
  • R 1 is H or C alkyl
  • R 2 is C alkyl which is unsubstituted or substituted with one or two hydroxyl groups
  • R 3 is H or unsubstituted CM alkyl
  • R 4 is H, unsubstituted C M alkyl or C(0)NR 5 R 6 ;
  • R 5 and R 6 which are the same or different, are independently selected from H and unsubstituted CM alkyl.
  • the compound of formula (I) is selected from formic acid and acetic acid; the compound of formula (II) is selected from methanol, ethanol and ethylene glycol; the compound of formula (III) is selected from formaldehyde and acetaldehyde; and the compound of formula (IV) is selected from ammonia and urea.
  • the compound is a compound of formula (I) which is formic acid.
  • said liquid phase comprises formic acid.
  • the catalyst is usually termed a formic acid
  • the catalyst used in the process of the invention for producing H 2 comprises polymetallic nanoparticles.
  • polymetallic nanoparticle as used herein means a nanoparticle which comprises more than one metal, i.e. it comprises two or more metals.
  • a polymetallic nanoparticle comprises only two metals, in which case the polymetallic nanoparticle is a bimetallic nanoparticle.
  • one or more further metals may be present too.
  • a polymetallic nanoparticle may comprise an alloy of two or more metals.
  • a polymetallic nanoparticle may have a "core-shell" structure.
  • a polymetallic nanoparticle may have a central core, and a shell surrounding the core, wherein the shell comprises a first metal and the core comprises a second metal, which second metal is different from the first metal.
  • the word is therefore intended to cover polymetallic nanoparticles in which the shell completely surrounds the core, such that the metal atoms on the surface of the nanoparticle are atoms of the first metal.
  • it is also intended to cover polymetallic nanoparticles in which the shell is incomplete, such that the majority of metal atoms on the surface of the nanoparticle are atoms of the first metal but some atoms of the second metal are also exposed.
  • the shell completely surrounds the core.
  • the molar ratio of the first (shell) metal to the second (core) metal can be selected such that the shell completely surrounds the core and no core metal atoms are exposed.
  • the process of the invention for producing H 2 comprises contacting a liquid phase comprising said compound of formula (I), (II), (III) or (IV) with the catalyst.
  • liquid phase in this context means that the compound of formula (I), (II), (III) or (IV) may be present in solution or as a neat liquid.
  • the liquid phase comprises said compound of formula (I), (II), (III) or (IV) as a neat liquid.
  • Other components, e.g. additives may be present in said neat compound of formula (I), (II), (III) or (IV).
  • the liquid phase may consist of said compound of formula (I), (II), (III) or (IV) as a neat liquid.
  • the liquid phase comprises said compound of formula (I), (II), (III) or (IV) and a solvent.
  • a solvent Any suitable solvent may be used.
  • the solvent comprises a polar protic solvent.
  • the solvent may comprise water or an alcohol.
  • the catalyst in the process of the invention for producing 3 ⁇ 4, can advantageously be used to generate hydrogen from the compound of formula (I), (II), (III) or (IV) at room temperature.
  • higher temperatures may also be used.
  • the step of contacting the liquid phase comprising said compound of formula (I), (II), (III) or (IV) with the catalyst is performed at a temperature which does not exceed 100 °C.
  • the contacting may for instance be performed at a temperature of from 0 °C to 100 °C. Lower temperatures may however be employed. Thus, said contacting may for instance be performed at a temperature which does not exceed 60 °C.
  • the contacting step is performed at a temperature of from 0 °C to 60 °C or for instance at a temperature of from 0 °C to 50 °C. In one embodiment, said contacting is performed at a temperature which does not exceed 40 °C. Typically, in this embodiment, the contacting step is performed at a temperature of from 0 °C to 40 °C or for instance at a temperature of from 0 °C to 30 °C.
  • the catalyst comprises (b) said nanoparticles which comprise a metal selected from palladium, rhodium, ruthenium, iridium, copper and silver.
  • These nanoparticles may be monometallic nanoparticles, i.e. nanoparticles in which the only metal present is the metal selected from palladium, rhodium, ruthenium, iridium, copper and silver.
  • the nanoparticles may be polymetallic, i.e. they may comprise said metal selected from palladium, rhodium, ruthenium, iridium, copper and silver and a further metal.
  • the nanoparticles which comprise a metal selected from palladium, rhodium, ruthenium, iridium, copper and silver are monometallic nanoparticles.
  • the nanoparticles (b) comprise a metal selected from palladium, rhodium, ruthenium and silver.
  • the catalyst comprises said nanoparticles (b) which comprise a metal selected from rhodium, ruthenium, iridium and copper.
  • nanoparticles may be monometallic nanoparticles, i.e. nanoparticles in which the only metal present is the metal selected from rhodium, ruthenium, iridium and copper.
  • the nanoparticles may be polymetallic, i.e. they may comprise said metal selected from rhodium, ruthenium, iridium and copper and a further metal.
  • the nanoparticles which comprise a metal selected from rhodium, ruthenium, iridium and copper are monometallic nanoparticles.
  • Said nanoparticles may have a mean particle size of less than or equal to 400 nm.
  • said nanoparticles may have a mean particle size of from 0.5 nm to 400 nm, or for instance from 1 nm to 400 nm.
  • the particle size distribution of the nanoparticles is such that 90 % of the particles have a particle size of less than 400 nm.
  • said nanoparticles have a mean particle size of less than or equal to
  • said nanoparticles may have a mean particle size of from 0.5 nm to 200 nm, or for instance from 1 nm to 200 nm.
  • the particle size distribution of the nanoparticles is such that 90 % of the particles have a particle size of less than 200 nm.
  • said nanoparticles have a mean particle size of less than or equal to 100 nm.
  • said nanoparticles may have a mean particle size of from 0.5 nm to 100 nm, or for instance from 1 nm to 100 nm.
  • the particle size is typically 0.5 nm to 100 nm, or for instance from 1 nm to 100 nm.
  • the distribution of the nanoparticles is such that 90 % of the particles have a particle size of less than 100 nm.
  • said nanoparticles have a mean particle size of less than or equal to 60 nm.
  • said nanoparticles may have a mean particle size of from 0.5 nm to 60 nm, or for instance from 1 nm to 60 nm.
  • nanoparticles is such that 90 % of the particles have a particle size of less than 60 nm.
  • said nanoparticles have a mean particle size of less than or equal to 50 nm.
  • said nanoparticles may have a mean particle size of from 0.5 nm to 50 nm, or for instance from 1 nm to 50 nm.
  • the particle size distribution of the nanoparticles is such that 90 % of the particles have a particle size of less than 50 nm.
  • said nanoparticles have a mean particle size of less than or equal to 20 nm.
  • said nanoparticles may have a mean particle size of from 0.5 nm to 20 nm, or for instance from 1 nm to 20 nm.
  • the particle size distribution of the nanoparticles is such that 90 % of the particles have a particle size of less than 20 nm.
  • said nanoparticles have a mean particle size of less than or equal to 15 nm.
  • said nanoparticles may have a mean particle size of from 0.5 nm to 15 nm, or for instance from 1 nm to 15 nm.
  • the particle size distribution of the nanoparticles is such that 90 % of the particles have a particle size of less than 15 nm.
  • said nanoparticles comprise a metal selected from palladium, rhodium and ruthenium.
  • the nanoparticles may for instance comprise a metal selected from palladium and rhodium.
  • the nanoparticles (b) may comprise a metal selected from ruthenium and rhodium.
  • Rhodium is a preferred metal.
  • the nanoparticles (b) comprise rhodium.
  • the nanoparticles (b) may comprise palladium.
  • the nanoparticles have a mean particle size of less than or equal to 10 nm. They may for instance have a mean particle size of less than or equal to 5 nm, or even less than or equal to 3 nm.
  • the nanoparticles may have a mean particle size of from 0.5 nm to 15 nm, or for instance from 1 nm to 15 nm.
  • the particle size distribution of the nanoparticles is such that 90 % of the particles have a particle size of less than 15 nm.
  • the nanoparticles may have a mean particle size of from 0.5 nm to 5 nm, or for instance from 0.5 nm to 3 nm.
  • the particle size distribution of the nanoparticles is such that 90 % of the particles have a particle size of less than 5 nm or less than 3 nm, as the case may be.
  • the catalyst comprises (a) said polymetallic nanoparticles.
  • the polymetallic nanoparticles comprise a core which comprises said second metal, and a shell surrounding said core, which shell comprises said first metal.
  • “Surrounding" in this context means completely surrounding, so that none of the core atoms are exposed, or partially surrounding, so that some of the core atoms are exposed.
  • the shell completely surrounds the core such that none of the core atoms are exposed.
  • said first metal is selected from palladium, platinum, rhodium or iridium. More typically, the first metal is palladium.
  • the work function of the second metal is less than the work function of the first metal.
  • the lower work function of the second (core) metal compared to the first (shell) metal causes charge transfer from the core (lower work function) to the shell (higher work function).
  • This in turn causes stronger adsorption of the compound of fomula (I), (II), (III), or (IV) onto the surface of the nanoparticle. This is thought to be due to increased back-bonding from the metal d-orbitals into the pi orbitals of the adsorbed molecule.
  • Work function here means the work function of the (1 11) crystal plane for metals having a face centred cubic (fee) lattice structure, or the work function of the (001) crystal plane for metals having a hexagonal closest packed (hep) lattice structure.
  • the second (core) metal typically has a work function which is lower than the work function of Pd, i.e. less than 5.6 eV.
  • the work function of the second metal is less than 5.6 eV. More typically, it is less than or equal to 5.3 eV. In a preferred embodiment, it is less than or equal to 5.0 eV.
  • the second metal is selected from: a d-block metal of any one of Groups 8, 9, 10, 1 1 and 12, a Group 1 (alkali) metal, or a Group 2 (alkaline earth) metal, provided that said second metal is other than said first metal. More typically, the second metal is selected from copper, silver, gold, nickel, palladium, platinum, cobalt, rhodium, iridium, ruthenium, iron, osmium, zinc, cadmium, lithium, sodium, potassium, rubidium, caesium, beryllium, magnesium, calcium, strontium and barium.
  • the second metal may for instance be selected from copper, silver, gold, nickel, palladium, platinum, cobalt, rhodium, iridium and ruthenium.
  • the second metal is selected from copper, silver, gold, platinum, rhodium and ruthenium. More typically, the second metal is silver or rhodium. In one embodiment, the second metal is silver.
  • the second metal is a d- block metal of any one of Groups 8, 9, 10, 11 and 12, a Group 1 (alkali) metal, or a Group 2 (alkaline earth) metal, provided that the second metal is other than palladium, platinum, gold, iron, cobalt and nickel.
  • the second metal is other than palladium, platinum, gold, iron, cobalt, nickel, titanium, tungsten, tantalum, vanadium and niobium.
  • said second metal is selected from silver, rhodium, ruthenium, copper and iridium. More typically, said second metal is silver, rhodium, ruthenium or copper.
  • said second metal may be silver, rhodium or copper. Preferably, it is silver or copper.
  • said second metal may be selected from silver, rhodium and ruthenium.
  • the second metal is silver.
  • the second metal may however be selected from rhodium and copper.
  • the second metal may be rhodium.
  • the second metal is copper.
  • the second metal is silver.
  • the first metal is palladium.
  • said catalyst comprises said polymetallic nanoparticles, which nanoparticles comprise a core which comprises said second metal, and a shell surrounding the core, which shell comprises said first metal which is palladium.
  • the polymetallic nanoparticles when polymetallic nanoparticles are employed as the catalyst in the process of the invention for producing 3 ⁇ 4, the polymetallic nanoparticles have a mean particle size of less than or equal to 50 nm.
  • said polymetallic nanoparticles may have a mean particle size of from 0.5 nm to 50 nm, or for instance from 1 nm to 50 nm.
  • the particle size distribution of the polymetallic nanoparticles is such that 90 % of the particles have a particle size of less than 50 nm. More typically, said polymetallic nanoparticles have a mean particle size of less than or equal to 40 nm.
  • said polymetallic nanoparticles may have a mean particle size of from 0.5 nm to 40 nm, or for instance from 1 nm to 40 nm.
  • the particle size distribution of the polymetallic nanoparticles is such that 90 % of the particles have a particle size of less than 40 nm.
  • said polymetallic nanoparticles have a mean particle size of less than or equal to 30 nm.
  • said polymetallic nanoparticles may have a mean particle size of from 0.5 nm to 30 nm, or for instance from 1 nm to 30 nm.
  • the particle size distribution of the polymetallic nanoparticles is such that 90 % of the polymetallic nanoparticles have a particle size of less than 30 nm.
  • said polymetallic nanoparticles have a mean particle size of less than or equal to 25 nm.
  • said polymetallic nanoparticles may have a mean particle size of from 0.5 nm to 25 nm, or for instance from 1 nm to 25 nm.
  • the particle size distribution of the polymetallic nanoparticles is such that 90 % of the polymetallic nanoparticles have a particle size of less than 25 nm. Even more typically, said polymetallic nanoparticles have a mean particle size * of less than or equal to 20 nm. For instance said polymetallic nanoparticles may have a mean particle size of from 0.5 nm to 20 nm, or for instance from 1 nm to 20 nm. Typically, the particle size distribution of the polymetallic nanoparticles is such that 90 % of the polymetallic nanoparticles have a particle size of less than 20 nm.
  • said polymetallic nanoparticles have a mean particle size of less than or equal to 15 nm.
  • said polymetallic nanoparticles may have a mean particle size of from 0.5 nm to 15 nm, or for instance from 1 nm to 15 nm.
  • the particle size distribution of the polymetallic nanoparticles is such that 90 % of the polymetallic nanoparticles have a particle size of less than 15 run.
  • said polymetallic nanoparticles have a mean particle size of less than or equal to 5 nm.
  • said polymetallic nanoparticles may have a mean particle size of from 0.5 nm to 5 nm, or for instance from 1 nm to 5 nm.
  • the particle size distribution of the polymetallic nanoparticles is such that 90 % of the polymetallic nanoparticles have a particle size of less than 5 nm.
  • the molar ratio of the second metal to the first metal in said polymetallic nanoparticles may for instance be from 3:1 to 1 :3.
  • molar ratios closer to 1:1 are often advantageous, resulting in the benefits associated with full coverage of the core by the shell (so that no core atoms are exposed) whilst at the same time the shell is thin enough for effective charge transfer from the core to the outer surface of the polymetallic nanoparticle (the metal in the shell typically having a higher work function than the metal in the core).
  • the molar ratio of the second metal to the first metal in said polymetallic nanoparticles is from 2.5:1 to 1 :2.5. More typically, it is from 2:1 to 1:2.
  • the molar ratio of the second metal to the first metal in said polymetallic nanoparticles is from 1.5:1 to 1 :1.5. More typically, the ratio is from 1.2:1 to 1 :1.2.
  • said molar ratio of the second metal to the first metal in said polymetallic nanoparticles is about 1 : 1.
  • said catalyst comprises said polymetallic nanoparticles, which polymetallic nanoparticles comprise a core which comprises said second metal, and a shell surrounding the core, which shell comprises said first metal, wherein the first metal is palladium and the second metal is silver.
  • these polymetallic palladium/silver nanoparticles have a mean particle size of less than or equal to 35 nm, preferably less than or equal to 25 nm, more preferably less than or equal to 20 nm. More typically, they have a mean particle size of from 1 nm to 35 nm, preferably from 10 run to 25 nm, more preferably from 17 to 20 nm.
  • the polymetallic nanoparticles have a mean particle size of from 1 nm to 20 nm, preferably from 10 nm to 20 nm, or in some cases from 17.0 to 20.0 nm.
  • the standard deviation from said mean is less than or equal to 5.0 nm. More typically, it is less than or equal to 3.0 nm.
  • the polymetallic nanoparticles comprise a core which comprises said second metal, and a shell surrounding the core, which shell comprises said first metal, wherein the first metal is palladium and the second metal is silver, and the polymetallic nanoparticles have a mean particle size of from 17.0 to 20.0 nm, wherein the standard deviation from said mean is less than or equal to 3.0 nm.
  • the silver cores of said polymetallic nanoparticles have a mean particle size of from 10.0 nm to 17.0 nm, preferably from 13.0 nm to 17.0 nm, more preferably about 15.0 nm.
  • the standard deviation from said mean is less than or equal to 3.5 nm. More typically, it is less than or equal to 1.5 nm.
  • the silver cores of said polymetallic nanoparticles have a mean particle size of about 15.0 nm, wherein the standard deviation from said mean is less than or equal to 1.5 nm.
  • the molar ratio of the silver to the palladium in said polymetallic nanoparticles is from 1.5: 1 to 1 :1.5. Preferably it is about 1 :1.
  • said catalyst comprises said polymetallic nanoparticles, which polymetallic nanoparticles comprise a core which comprises said second metal, and a shell surrounding the core, which shell comprises said first metal, wherein the first metal is palladium and the second metal is rhodium.
  • the polymetallic nanoparticles have a mean particle size of less than or equal to 4 nm.
  • the polymetallic nanoparticles may have a mean particle size of from 0.5 nm to 4 nm.
  • the standard deviation from said mean is less than or equal to 1.0 nm. More typically, it is less than or equal to 0.5 nm.
  • the polymetallic nanoparticles have a mean particle size of from 2.3 to 3.5 nm, wherein the standard deviation from said mean is less than or equal to 0.5 nm.
  • the rhodium cores of said polymetallic nanoparticles have a mean particle size of about 0.5 to 2.5 nm, preferably from 1.5 to 2.5 nm, more preferably about 2.0 nm.
  • the standard deviation from said mean is less than or equal to 0.5 nm, or for instance less than or equal to about 0.4 nm. More typically, it is less than or equal to 0.2 nm. More typically, the rhodium cores of said polymetallic nanoparticles have a mean particle size of about 2.0 nm, wherein the standard deviation from said mean is less than or equal to 0.2 nm.
  • the molar ratio of the rhodium to the palladium in said polymetallic nanoparticles is from 1.5: 1 to 1 : 1.5, preferably wherein said molar ratio is about 1 : 1.
  • said catalyst comprises said polymetallic nanoparticles, which polymetallic nanoparticles comprise a core which comprises said second metal, and a shell surrounding the core, which shell comprises said first metal, wherein the first metal is palladium and the second metal is ruthenium.
  • these polymetallic nanoparticles have a mean particle size of less than or equal to 5 nm. More typically, the polymetallic nanoparticles have a mean particle size of from 0.5 nm to 5 nm.
  • the polymetallic nanoparticles may for instance have a mean particle size of from 2.6 to 4.0 nm. Typically, the standard deviation from said mean is less than or equal to 2.0 nm. More typically, it is less than or equal to 1.0 nm, for instance less than or equal to 0.6 nm. Thus, in one embodiment the polymetallic nanoparticles have a mean particle size of from 2.6 to 4.0 nm, wherein the standard deviation from said mean is less than or equal to 0.6 nm.
  • the ruthenium cores of said polymetallic nanoparticles may have a mean particle size of about 1.0 to 2.6 nm. Typically, the standard deviation from said mean is less than or equal to 1.0 nm, more typically less than or equal to 0.5 nm, for instance less than or equal to 0.2 nm. Thus, for instance, the ruthenium cores of said polymetallic nanoparticles may have a mean particle size of about 2.3 nm, wherein the standard deviation from said mean is less than or equal to 0.2 nm.
  • the molar ratio of the ruthenium to the palladium in said polymetallic nanoparticles is from 1.5: 1 to 1 : 1.5, preferably wherein said molar ratio is about 1 : 1.
  • said catalyst comprises said polymetallic nanoparticles, which polymetallic nanoparticles comprise a core which comprises said second metal, and a shell surrounding the core, which shell comprises said first metal, wherein the first metal is palladium and the second metal is gold.
  • the polymetallic nanoparticles have a mean particle size of less than or equal to 15 nm.
  • the polymetallic nanoparticles may for instance have a mean particle size of from 1.0 to 15.0 nm. Typically, the standard deviation from said mean is less than or equal to 2.5 nm. More typically,- it is less than or equal to 1.5 nm.
  • the polymetallic nanoparticles may for instance have a mean particle size of from 8.0 to 12.0 nm, wherein the standard deviation from said mean is less than or equal to 1.5 nm.
  • the molar ratio of the gold to the palladium in said polymetallic nanoparticles is from 1.5 : 1 to 1 : 1.5, preferably wherein said molar ratio is about 1 : 1.
  • said catalyst comprises said polymetallic nanoparticles, which polymetallic nanoparticles comprise a core which comprises said second metal, and a shell surrounding the core, which shell comprises said first metal, wherein the first metal is palladium and the second metal is platinum.
  • these polymetallic nanoparticles have a mean particle size of less than or equal to 15 nm.
  • the polymetallic nanoparticles may have a mean particle size of from 1 nm to 15 nm. Typically, the standard deviation from said mean is less than or equal to 4.5 nm. More typically, it is less than or equal to 2.5 nm.
  • the polymetallic nanoparticles may have a mean particle size of from 8.0 to 12.0 nm, wherein the standard deviation from said mean is less than or equal to 2.5 nm.
  • the platinum cores of said nanoparticles have a mean particle size of from 2.0 to 8.0 nm, preferably from 3.0 to 7.0 nm, more preferably from 5.0 to 6.0 nm.
  • the standard deviation from said mean is less than or equal to 3.5 nm. More typically, it is less than or equal to 2.5 nm, for instance less than or equal to 1.5 nm.
  • the platinum cores of said nanoparticles have a mean particle size of about 5.0 to 6.0 nm, wherein the standard deviation from said mean is less than or equal to 1.5 nm.
  • the molar ratio of the platinum to the palladium in said polymetallic nanoparticles is from 1.5: 1 to 1 :1.5, preferably wherein said molar ratio is about 1 : 1.
  • said catalyst comprises said polymetallic nanoparticles, which polymetallic nanoparticles comprise an alloy comprising said first metal and said second metal, wherein said first metal is silver or platinum, and said second metal is palladium.
  • these polymetallic nanoparticles have a mean particle size of less than or equal to 25 nm, preferably less than or equal to 15 nm, more preferably less than or equal to 10 nm.
  • the polymetallic nanoparticles have a mean particle size of from 1 nm to 25 nm, preferably from 1 nm to 1 nm, more preferably from 1 nm to 10 nm.
  • the catalyst used in the process of the invention for producing H 2 typically further comprises a polymer.
  • the polymer is typically referred to as a stabilising polymer.
  • the polymer may for instance be polyvinyl pyrrolidone) (PVP), polyvinyl alcohol) (PVA) or poly(ethylenimine) (PEI)-It has been found that the presence of certain polymers can improve the activity of decomposition of a compound of formula (I), (II), (III) or (IV) (typically formic acid), to produce hydrogen.
  • PVP polyvinyl pyrrolidone
  • PVA polyvinyl alcohol
  • PEI poly(ethylenimine)
  • the presence of certain polymers can improve the rate and total volume of hydrogen production at lower temperatures such as room temperature.
  • One category of polymer that has been particularly useful in this regard is a polymer bearing pendant amine groups.
  • Poly(ethylenimine) (PEI) is an example of such a polymer.
  • the catalyst used in the process of the invention for producing H 2 further comprises a polymer.
  • said polymer is a polymer which comprises a plurality of amino, Ci.io alkylamino and/or di(C 1- jo)alkylamino groups.
  • the polymer is poly(ethylenimine) (PEI).
  • the catalyst used in the process of the invention for producing H 2 may or may not further comprise a solid support material, in addition to said nanoparticles or said polymetallic nanoparticles, wherein the nanoparticles or polymetallic nanoparticles are supported on said support material.
  • a solid support material Any suitable support material may be used, for instance the solid support material may comprise carbon, alumina or titania. Typically, however, it comprises carbon.
  • the support comprises an oxide, a nitride, carbon or nanotubes.
  • the nanotubes are usually carbon nanotubes.
  • the oxide is typically a metal oxide.
  • the nitride is typically a metal nitride.
  • the nanoparticles or polymetallic nanoparticles are typically present in an amount of from 10 to 30 weight %, based on the total weight of the catalyst including the support, preferably in an amount of from 15 to 25 weight %, based on the total weight of the catalyst including the support.
  • the catalyst does not comprise a solid support material.
  • the nanoparticles or polymetallic nanoparticles may be unsupported.
  • the nanoparticles or polymetallic nanoparticles may be present as a suspension, for instance a colloidal suspension, in the liquid phase employed in the process of the invention.
  • the nanoparticles or polymetallic nanoparticles may for instance initially be present in the solid state, and subsequently contacted with the liquid phase, to form a colloidal suspension of the nanoparticles or polymetallic nanoparticles in the liquid phase.
  • a suspension typically a colloidal suspension, of the nanoparticles or polymetallic nanoparticles in a solvent may be contacted with said liquid phase, resulting in a colloidal suspension of said nanoparticles or said polymetallic nanoparticles in said liquid phase.
  • said step of contacting of said liquid phase with said catalyst results in a colloidal suspension of said nanoparticles or said polymetallic nanoparticles in said liquid phase.
  • the liquid phase does not comprise a solvent, but comprises a neat liquid which is the compound of formula (I), (II), (III) or (IV).
  • the liquid phase may comprise neat formic acid.
  • the liquid phase consists of, or consists essentially of, the compound of formula (I), (II), (III) or (IV).
  • the liquid phase may consist of, or consist essentially of, formic acid.
  • the liquid phase comprises said compound of formula (I), (II), (III) or (IV) and a solvent.
  • the liquid phase may comprise formic acid and a solvent. Any suitable solvent may be used.
  • the solvent comprises a polar protic solvent, for instance an alcohol or water.
  • the solvent comprises water.
  • the concentration of said compound of formula (I), (II), (III) or (IV) in said liquid phase is typically from 0.01 M to 26.52 M, more typically from 0.1 M to 10.0 M.
  • the concentration of said compound of formula (I), (II), (III) or (IV) may be from 0.01 M to 20.0 M, or for instance from 0.5 M to 10.0 M.
  • the concentration of the compound in the liquid phase is from 0.2 M to 5.0 M, from 0.3 M to 5.0 M. More typically, it is from 0.5 M to 5.0 M, or for instance from 0.5 to 4.0 M.
  • the concentration of the compound of formula (I), (II), (III) or (IV) in said liquid phase is from 0.3 M to 6.0 M, or for instance from 0.3 M to 5.0 M. In other embodiments, however, it is from 0.4 M to 3.0 M, of for instance from 0.5 M to 2.5 M.
  • the concentration of the compound of formula (I), (II), (III) or (IV) in said liquid phase is from 0.5 M to 1.6 M. More typically, in these embodiments, it is from 0.6 M to 1.4 M, or for instance from 0.7 M to 1.3 M. Usually, it is from 0.8 M to 1.2 M, or for instance from 0.9 M to 1.1 M, i.e. about 1 M. Typically, in these embodiments, it is from 0.5 M to 1.6 M. More typically, in these embodiments, it is from 0.6 M to 1.4 M, or for instance from 0.7 M to 1.3 M. Usually, it is from 0.8 M to 1.2 M, or for instance from 0.9 M to 1.1 M, i.e. about 1 M. Typically, in these
  • the compound of formula (I), (II), (III) or (IV) is formic acid.
  • the catalyst may be any of the catalysts defined above. More typically, however, it is a catalyst which comprises said polymetallic nanoparticles, which polymetallic nanoparticles comprise a core which comprises silver and a shell surrounding the core, which shell comprises palladium.
  • the hydrogen generation activity of such systems is shown in Fig. 26 filed herewith. 5
  • the concentration of said catalyst in the liquid phase is less than or equal to 0.01 M, preferably less than or equal to 0.005 M, more preferably less than or equal to 0.0005 M.
  • the process of the invention for producing 3 ⁇ 4 may further comprise recovering said H 2 .
  • the process of the invention produces a mixture of gases comprising hydrogen gas, for instance a mixture of 3 ⁇ 4 and C0 .
  • the step of recovering said H 2 typically therefore comprises collecting the product gas mixture and separating the 3 ⁇ 4 from said mixture.
  • the separation may be effected by any suitable method known in the art, for instance by using a filter material which selectively retains contaminants and lets the hydrogen pass through.
  • the separated 3 ⁇ 4 gas may also for instance be compressed and/or stored for later use.
  • the compound of formula (I), (II), (III) or (IV) is formic acid.
  • said compound of formula (I), (II), (III) or (IV) is formic acid.
  • gaseous product mixture comprising H 2 and C0 2 .
  • gaseous product mixture comprises a 1 :1 molar ratio of H 2 and C0 2 .
  • gaseous product mixture comprises no more than lOppm by volume carbon monoxide.
  • said compound of formula (I), (II), (III) or (IV) is formic acid and the production of 3 ⁇ 4 from formic acid occurs in a single step, in accordance with the following reaction:
  • the present invention provides a process for producing H 2 from a compound of formula (I), (II), (III) or (IV): R'COOH (I)
  • R 1 is H or unsubstituted or substituted CMO alkyl
  • R 2 is unsubstituted or substituted Q.io alkyl
  • R 3 is H or unsubstituted or substituted CMO alkyl
  • R 4 is H, unsubstituted or substituted Ci -!0 alkyl, or C(0)NR 5 R 6 ;
  • R 5 and R 6 which are the same or different, are independently selected from H and unsubstituted or substituted CMO alkyl;
  • nanoparticles which comprise a metal selected from palladium, rhodium,
  • ruthenium, iridium, copper and silver or - polymetallic nanoparticles, each of which comprises a first metal and a second metal, which first metal is selected from a Group 9, Group 10, Group 1 1 or Group 12 d-block metal, and which second metal is other than said first metal.
  • the polymetallic nanoparticles comprise a core which comprises said second metal, and a shell surrounding said core, which shell comprises said first metal.
  • “surrounding” in this context means completely surrounding, so that none of the core atoms are exposed, or partially surrounding, so that some of the core atoms are exposed.
  • the shell completely surrounds the core such that none of the core atoms are exposed.
  • the polymetallic nanoparticles may comprise an alloy comprising said first metal and said second metal.
  • This process may be as further defined hereinbefore on pages 13 to 27.
  • the catalyst used in this process may also be as further defined anywhere herein for the processes or the catalysts of the invention.
  • the invention provides a catalyst for the production of hydrogen from a compound of formula (I), (II), (III) or (IV), or for the electro-oxidation of a compound of formula (I), (II), (III) or (IV):
  • R 1 is H or unsubstituted or substituted d-io alkyl
  • R 2 is unsubstituted or substituted C 1-10 alkyl
  • R 3 is H or unsubstituted or substituted C O alkyl
  • R 4 is H, unsubstituted or substituted C M0 alkyl, or C(0)NR 5 R 6 ;
  • R 5 and R 6 which are the same or different, are independently selected from H and unsubstituted or substituted CMO alkyl;
  • the catalyst comprises polymetallic nanoparticles, which polymetallic nanoparticles comprise a core and a shell surrounding the core; wherein the shell comprises a first metal which is palladium, and the core comprises a second metal, wherein the second metal is other than palladium, platinum, gold, iron, cobalt, nickel, titanium, tungsten, tantalum, vanadium and niobium.
  • the catalyst of the invention is for the production of formic acid or for the electro-oxidation of formic acid.
  • the second metal in the catalyst of the invention is a d-block metal of any one of Groups 8, 9, 10, 11 and 12, a Group 1 (alkali) metal, or a Group 2 (alkaline earth) metal, provided that the second metal is other than palladium, platinum, gold, iron, cobalt and nickel. More typically, the second metal is a said d-block metal of any one of Groups 8, 9, 10, 11 and 12.
  • the work function of the second metal is less than the work function of the first metal, palladium.
  • This is advantageous in core-shell type polymetallic nanoparticles, because the lower work function of the second (core) metal compared to the palladium shell causes charge transfer from the core to the shell. This in turn causes stronger adsorption of the compound of fomula (I), (II), (III), or (IV) onto the surface of the nanoparticle. This is thought to be due to increased back-bonding from the metal d-orbitals into the pi orbitals of the adsorbed molecule.
  • Work function here means the work function of the (11 1) crystal plane for metals having a face centred cubic (fee) lattice structure, or the work function of the (001) crystal plane for metals having a hexagonal closest packed (hep) lattice structure.
  • the second (core) metal typically has a work function which is lower than the work function of Pd, i.e. less than 5.6 eV.
  • the work function of the second metal is less than 5.6 eV. More typically, it is less than or equal to 5.3 eV. In a preferred embodiment, it is less than or equal to 5.0 eV.
  • the second metal is an electron-rich
  • d-block a d-block metal of any one of Groups 8, 9, 10; 1 1 and 12 provided that the second metal is other than palladium, platinum, gold, iron, cobalt and nickel.
  • said second metal is selected from silver, rhodium, ruthenium, copper, iridium, osmium, zinc, cadmium, lithium, sodium, potassium, rubidium, caesium, beryllium, magnesium, calcium, strontium and barium. More typically, said second metal is selected from silver, rhodium, ruthenium, copper and iridium. In one embodiment, the second metal is selected from copper, silver, rhodium and ruthenium. Thus, the second metal may for instance be silver or rhodium. In a preferred embodiment, the second metal is silver.
  • Said second metal may for instance be silver, rhodium or copper. Preferably, it is silver or copper. Alternatively, said second metal may be selected from silver, rhodium and ruthenium.
  • the second metal is silver.
  • the second metal may however be selected from rhodium and copper.
  • the second metal may be rhodium.
  • the second metal is copper
  • the polymetallic nanoparticles of the catalyst of the invention have a mean particle size of less than or equal to 50 nm.
  • said polymetallic nanoparticles may have a mean particle size of from 0.5 nm to 50 nm, or for instance from 1 nm to 50 nm.
  • the particle size distribution of the polymetallic nanoparticles is such that 90 % of the particles have a particle size of less than 50 nm.
  • said polymetallic nanoparticles have a mean particle size of less than or equal to 40 nm.
  • said polymetallic nanoparticles may have a mean particle size of from 0.5 nm to 40 nm, or for instance from 1 nm to 40 nm.
  • the particle size distribution of the polymetallic nanoparticles is such that 90 % of the particles have a particle size of less than 40 nm.
  • said polymetallic nanoparticles of the catalyst of the invention have a mean particle size of less than or equal to 30 nm.
  • said polymetallic nanoparticles may have a mean particle size of from 0.5 nm to 30 nm, or for instance from 1 nm to 30 nm.
  • the particle size distribution of the polymetallic nanoparticles is such that 90 % of the polymetallic nanoparticles have a particle size of less than 30 nm. More typically, said polymetallic nanoparticles of the catalyst of the invention have a mean particle size of less than or equal to 25 nm.
  • said polymetallic nanoparticles may have a mean particle size of from 0.5 nm to 25 nm, or for instance from " " " ' 1 nm to 25 nm.
  • the particle size distribution of the polymetallic nanoparticles is such that 90 % of the polymetallic nanoparticles have a particle size of less than 25 nm.
  • said polymetallic nanoparticles have a mean particle size of less than or equal to 20 nm.
  • said polymetallic nanoparticles may have a mean particle size of from 0.5 nm to 20 nm, or for instance from 1 nm to 20 nm.
  • the particle size distribution of the polymetallic nanoparticles is such that 90 % of the polymetallic nanoparticles have a particle size of less than 20 nm.
  • said polymetallic nanoparticles have a mean particle size of less than or equal to 15 nm.
  • said polymetallic nanoparticles may have a mean particle size of from 0.5 nm to 15 nm, or for instance from 1 nm to 15 nm.
  • the particle size distribution of the polymetallic nanoparticles is such that 90 % of the polymetallic nanoparticles have a particle size of less than 15 nm. More typically, said polymetallic nanoparticles have a mean particle size of less than or equal to 5 nm.
  • said polymetallic nanoparticles may have a mean particle size of from 0.5 nm to 5 nm, or for instance from 1 nm to 5 nm.
  • the particle size distribution of the polymetallic nanoparticles is such that 90 % of the polymetallic nanoparticles have a particle size of less than 5 nm.
  • the molar ratio of the second metal to the first metal in said polymetallic nanoparticles of the catalyst of the invention may for instance be from 3:1 to 1 :3.
  • molar ratios closer to 1 : 1 are often advantageous, resulting in the benefits associated with full coverage of the core by the shell (so that no core atoms are exposed) whilst at the same time the shell is thin enough for effective charge transfer from the core to the outer surface of the polymetallic nanoparticle (the metal in the shell typically having a higher work function than the metal in the core).
  • the molar ratio of the second metal to the first metal in said polymetallic nanoparticles is from 2.5:1 to 1 :2.5. More typically, it is from 2:1 to 1 :2.
  • the molar ratio of the second metal to the first metal in said polymetallic nanoparticles is from 1.5: 1 to 1 : 1.5. More typically, the ratio is from 1.2: 1 to 1:1.2. Usually, said molar ratio of the second metal to the first metal in said polymetallic nanoparticles is about 1 :1.
  • the second metal is silver.
  • these polymetallic palladium/silver nanoparticles have a mean particle size of less than or equal to 35 nm, preferably less than or equal to 25 nm, more preferably less than or equal to 20 nm. More typically, they have a mean particle size of from 1 nm to 35 nm, preferably from 10 nm to 25 nm, more preferably from 17 to 20 nm.
  • the polymetallic nanoparticles have a mean particle size of from 1 nm to 20 nm, preferably from 10 nm to 20 nm, or in some cases from 17.0 to 20.0 nm.
  • the standard deviation from said mean is less than or equal to 5.0 nm.
  • the polymetallic nanoparticles have a mean particle size of from 17.0 to 20.0 nm, wherein the standard deviation from said mean is less than or equal to 3.0 nm.
  • the silver cores of said polymetallic nanoparticles have a mean particle size of from 10.0 nm to 17.0 nm, preferably from 13.0 nm to 17.0 nm, more preferably about 15.0 nm.
  • the standard deviation from said mean is less than or equal to 3.5 nm. More typically, it is less than or equal to 1.5 nm.
  • the silver cores of said polymetallic nanoparticles have a mean particle size of about 15.0 nm, wherein the standard deviation from said mean is less than or equal to 1.5 nm.
  • the molar ratio of the silver to the palladium in said polymetallic nanoparticles is from 1.5:1 to 1:1.5. Preferably it is about 1 :1.
  • the second metal is rhodium.
  • the polymetallic nanoparticles have a mean particle size of less than or equal to 4 nm.
  • nanoparticles may have a mean particle size of from 0.5 nm to 4 nm. Typically, the standard deviation from said mean is less than or equal to 1.0 nm. More typically, it is less than or equal to 0.5 nm. Thus, for instance, the polymetallic nanoparticles may have a mean particle size of from 2.3 to 3.5 nm, wherein the standard deviation from said mean is less than or equal to 0.5 nm.
  • the rhodium cores of said polymetallic nanoparticles have a mean particle size of about 0.5 to 2.5 nm, preferably from 1.5 to 2.5 nm, more preferably about 2.0 nm.
  • the standard deviation from said mean is less than or equal to 0.5 nm, or for instance less than or equal to about 0.4 nm. More typically, it is less than or equal to 0.2 nm. More typically, the rhodium cores of said polymetallic nanoparticles have a mean particle size of about 2.0 nm, wherein the standard deviation from said mean is less than or equal to 0.2 nm.
  • the molar ratio of the rhodium to the palladium in said polymetallic nanoparticles is from 1.5: 1 to 1 : 1.5, preferably wherein said molar ratio is about 1 : 1.
  • the second metal is ruthenium.
  • the polymetallic nanoparticles have a mean particle size of less than or equal to 5 rim. More typically, the polymetallic nanoparticles have a mean particle size of from 0.5 nm to 5 nm. The polymetallic nanoparticles may for instance have a mean particle size of from 2.6 to 4.0 nm. Typically, the standard deviation from said mean is less than or equal to 2.0 nm. More typically, it is less than or equal to 1.0 nm, for instance less than or equal to 0.6 nm.
  • the polymetallic nanoparticles have a mean particle size of from 2.6 to 4.0 nm, wherein the standard deviation from said mean is less than or equal to 0.6 nm.
  • the ruthenium cores of said polymetallic nanoparticles may have a mean particle size of about 1.0 to 2.6 nm.
  • the standard deviation from said mean is less than or equal to 1.0 nm, more typically less than or equal to 0.5 nm, for instance less than or equal to 0.2 nm.
  • the ruthenium cores of said polymetallic nanoparticles may have a mean particle size of about 2.3 nm, wherein the standard deviation from said mean is less than or equal to 0.2 nm.
  • the molar ratio of the ruthenium to the palladium in said polymetallic nanoparticles is from 1.5: 1 to 1 : 1.5, preferably wherein said molar ratio is about 1 :1.
  • the catalyst of the invention further comprises a polymer.
  • the polymer is typically refened to as a stabilising polymer.
  • the polymer may for instance be polyvinyl pyrrolidone) (PVP), poly( vinyl alcohol) (PVA) or poly(ethylenimine) (PEI).
  • the presence of certain polymers can improve the activity of decomposition of a compound of formula (I), (II), (III) or (IV) (typically formic acid), to produce hydrogen.
  • the presence of certain polymers can improve the rate and total volume of hydrogen production at lower temperatures such as room temperature.
  • One category of polymer that has been particularly useful in this regard is a polymer bearing pendant amine groups.
  • Poly(ethylenimine) (PEI) is an example of such a polymer.
  • the catalyst of the invention further comprises a polymer.
  • said polymer is a polymer which comprises a plurality of amino, CMO alkylamino and/or di(Ci- io)alkylamino groups.
  • the polymer is poly(ethylenimine) (PEI).
  • the catalyst of the invention may or may not further comprise a solid support material, in addition to said polymetallic nanoparticles, wherein the polymetallic nanoparticles are supported on said solid support material.
  • a solid support material may be used, for instance the solid support material may comprise carbon, alumina or titania. Typically, however, it comprises carbon. A carbon is preferred when the catalyst is used in a fuel cell.
  • the support comprises an oxide, a nitride, carbon or nanotubes.
  • the nanotubes are usually carbon nanotubes.
  • the oxide is typically a metal oxide.
  • the nitride is typically a metal nitride.
  • the polymetallic nanoparticles are typically present in an amount of from 10 to 30 weight %, based on the total weight of the catalyst including the support, preferably in an amount of from 15 to 25 weight %, based on the total weight of the catalyst including the support.
  • the second metal in the catalyst of the invention is silver and the polymetallic nanoparticles have a mean particle size of less than or equal to 40 nm. More typically, in this embodiment, the polymetallic nanoparticles have a mean particle size of from 1 nm to 40 nm, from 10 nm to 40 nm, or from 20 nm to 40 nm.
  • the polymetallic nanoparticles may have a mean particle size of from 30.0 to 40.0 nm. Typically, the standard deviation from said mean is less than or equal to 5.0 nm. Usually, in this embodiment, the molar ratio of the silver to the palladium in said polymetallic nanoparticles is from 1.5:1 to 1 : 1.5. More typically, wherein said molar ratio is about 1: 1.
  • the catalyst does not comprise a solid support material.
  • the polymetallic nanoparticles may be unsupported.
  • the nanoparticles or polymetallic nanoparticles may be present as a suspension in a solvent (for instance a colloidal suspension in the solvent), or simply in powder form. Any suitable solvent may be used, but the solvent typically comprises a polar protic solvent, for instance an alcohol or water.
  • the invention provides a catalyst for the production of hydrogen from a compound of formula (I), (II), (III) or (IV), or for the electro-oxidation of a compound of formula (I), (II), (III) or (IV):
  • R 1 is H or unsubstituted or substituted C O alkyl
  • R is unsubstituted or substituted C 1-10 alkyl
  • R 3 is H or unsubstituted or substituted C O alkyl
  • R 4 is H, unsubstituted or substituted C 1-10 alkyl, or C(0)NR 5 R 6 ;
  • R s and R 6 which are the same or different, are independently selected from H and unsubstituted or substituted C] -10 alkyl;
  • the catalyst comprises polymetallic nanoparticles, which polymetallic nanoparticles comprise a core and a shell surrounding the core; wherein the shell comprises a first metal which is palladium, and the core comprises a second metal, wherein the second metal is other than palladium, platinum and gold.
  • the catalyst is for the production of formic acid or for the electro-oxidation of formic acid.
  • the second metal in the catalyst is a d-block metal of any one of Groups 8, 9, 10, 11 and 12, a Group 1 (alkali) metal, or a Group 2 (alkaline earth) metal, provided that the second metal is other than palladium, platinum and gold. More typically, the second metal is a d-block metal of any one of Groups 8, 9, 10, 1 1 and 12.
  • the work function of the second metal is less than the work function of the first metal, palladium.
  • This is advantageous in core-shell type polymetallic nanoparticles, because the lower work function of the second (core) metal compared to the palladium shell causes charge transfer from the core to the shell. This in turn causes stronger adsorption of the compound of fomula (I), (II), (III), or (IV) onto the surface of the nanoparticle. This is thought to be due to increased back-bonding from the metal d-orbitals into the pi orbitals of the adsorbed molecule.
  • Work function here means the work function of the (1 1 1) crystal plane for metals having a face centred cubic (fee) lattice structure, or the work function of the (001) crystal plane for metals having a hexagonal closest packed ⁇ hep) lattice structure.
  • the second (core) metal typically has a work function which is lower than the work function of Pd, i.e. less than 5.6 eV.
  • the work function of the second metal is less than 5.6 eV. More typically, it is less than or equal to 5.3 eV. In a preferred embodiment, it is less than or equal to 5.0 eV.
  • the second metal is an electron-rich
  • d-block a d-block metal of any one of Groups 8, 9, 10, 11 and 12.
  • said second metal is selected from silver, rhodium, ruthenium, copper, iridium, nickel, cobalt, iron, osmium, zinc, cadmium, lithium, sodium, potassium, rubidium, caesium, beryllium, magnesium, calcium, strontium and barium. More typically, said second metal is selected from silver, rhodium, ruthenium, copper, iridium, nickel and cobalt. In one embodiment, the second metal is selected from copper, silver, rhodium and ruthenium. Thus, the second metal may for instance be silver or rhodium. In a preferred embodiment, the second metal is silver.
  • the catalyst may be as further defined hereinbefore for the catalyst of the invention (see pages 29 to 35).
  • the above-defined catalyst may be produced by the process of the invention for producing said catalyst, which process comprises:
  • Step (b) is typically performed after step (a), in a sequential reduction process. However, for some second metals, step (b) be performed at the same time as step (a), in a co-reduction process.
  • any suitable palladium salt may be used: such Pd salts are well known in the art. Typically, however, the palladium salt is palladium nitrate.
  • any suitable solvents may be employed as the first and second solvents.
  • the first solvent comprises a polar protic solvent.
  • an alcohol or water, or a glycol, for instance ethylene glycol may be employed as the first solvent.
  • the second solvent also usually comprises a polar protic solvent.
  • an alcohol or water, or a glycol, for instance ethylene glycol may be employed as the second solvent.
  • the process of the invention for producing the catalyst of the invention may advantageously make use of stabilising polymers.
  • the process of the invention for producing the catalyst of the invention typically comprises:
  • Step (b) is typically performed after step (a), but may, for some second metals, be performed at the same time as step (a).
  • the sequential reduction process may comprise a hydrogen sacrificial protective step. Without such a step, metals which have a reduction potential which is lower than that of Pd, such as Rh and Ru, tend to segregate to the surface of particles produced during reduction, instead of remaining at the core.
  • a hydrogen sacrificial protective strategy can advantageously be used in order to obtain a Pd shell around metals having a lower reduction potential than Pd ("reversed" core-shell nanoparticles).
  • the process of the invention for producing the catalysts of the invention comprises:
  • the first and second stabilising polymers are independently selected from polyvinyl pyrrolidone) (PVP), polyvinyl alcohol) (PVA) and poly(ethylenimine) (PEI).
  • said suspension or solution of core nanoparticles produced in step (a) is a colloidal suspension or solution.
  • step (a) the step of reducing said salt of said second metal is performed by heating said salt in the presence of said first solvent and, when present, said stabilising polymer, under an inert atmosphere.
  • the salt of said second metal is heated to a temperature of at least 80 °C, preferably to a temperature of from 80 °C to 170 °C, preferably for a duration of at least 2 hours.
  • step (b), or step (b2) the step of reducing said palladium salt is performed by heating said salt in the presence of said second solvent and, when present, said second stabilising polymer, under an inert atmosphere.
  • the palladium salt is heated to a temperature of at least 80 °C, preferably to a temperature of from 80 °C to 100 °C, preferably for a duration of at least 2 hours.
  • Step (a) of the process of the invention may or may not further comprise isolating said core nanoparticles from said solvent.
  • step (b), or step (b2) may or may not further comprise isolating said polymetallic nanoparticles from said solvent.
  • Supported catalysts of the invention may be produced by employing a further step
  • the process further comprises (c) depositing said polymetallic nanoparticles on a support material, thereby producing a catalyst which comprises said polymetallic nanoparticles and a support material, wherein the polymetallic nanoparticles are supported on said support material.
  • the process may further comprise: (d) heating said catalyst to remove any residual stabilising polymer.
  • the catalysts of the invention may be used as catalysts for the electro-oxidation of a compound of formula (I), (II), (III) or (IV), as defined hereinbefore, to produce protons (H*).
  • electro-oxidation means oxidation at the surface of an electrode. It is thought that when a compound of formula (I), (II), (III) or (IV) is contacted with an electrode comprising the catalyst of the present invention, the compound is adsorbed onto the surface of the catalyst, and the catalyst catalyses cleavage of hydrogen atoms from the adsorbed molecules. The adsorbed hydrogen atoms are then converted into protons at the electrode. C-H bond cleavage is thought to be the rate-determining step.
  • the catalysts of the present invention can catalyse the electro- oxidation of a compound of formula (I), (II), (III) or (IV), as defined hereinbefore, to produce protons (H + ) at an electrode.
  • catalysts of the invention can be used as the catalyst in a fuel cell electrode, in fuel cells in which the fuel is a compound of formula (I), (II), (III) or (IV) as defined hereinbefore.
  • Such fuel cells are powered by the electro-oxidation of a said compound of formula (I); (II), (III) or (IV).
  • DFAFC direct formic acid fuel cell
  • the electro-oxidation reaction at the anode is very similar to the catalytic decomposition of formic acid to H 2 and C0 2 , and it is this reaction at the anode which is catalysed by the catalysts of the present invention.
  • C-H breakage is the rate-limiting, step, but this time protons are formed instead of hydrogen gas.
  • the present invention provides a process for the electro-oxidation of a compound of formula (I), (II), (III) or (IV), which compound is as defined hereinbefore, which process comprises contacting a liquid phase which comprises said compound of formula (I), (II), (III) or (IV) with a catalyst of the invention in the presence of an electrode.
  • the process is for the electro-oxidation of a compound of formula (I), (II), (III) or (IV) to produce protons at said electrode.
  • the catalyst of the invention may be as defined hereinbefore.
  • the liquid phase with which the catalyst is contacted may also be as further defined hereinbefore for the process of the invention for producing 3 ⁇ 4.
  • the invention provides a process for the electro-oxidation of a compound of formula (I), (II), (III) or (IV) as defined above; which process comprises contacting a liquid phase which comprises said compound of formula (I), (II), (III) or (IV) with an electrode, which electrode comprises a catalyst of the invention as defined hereinbefore.
  • the process is for the electro-oxidation of a compound of formula (I), (II), (III) or (IV) to produce protons at said electrode.
  • the electrode comprises a conducting substrate and a catalyst of the invention as defined hereinbefore.
  • the liquid phase may be as further defined hereinbefore for the process of the invention for producing 3 ⁇ 4.
  • the invention further provides the use of a catalyst of the invention as defined hereinbefore for the electro-oxidation of a compound of formula (I), (II), (III) or (IV), which compound of formula (I), (II), (III) or (IV) is as defined hereinbefore.
  • the invention further provides the use of a catalyst of the invention as defined hereinbefore for the electro-oxidation of a compound of formula (I), (II), (III) or (IV) as defined hereinbefore to produce protons at an electrode.
  • the electrode comprises the catalyst of the invention. More typically, the electrode comprises a conducting substrate and a catalyst of the invention as defined hereinbefore.
  • the compound is typically a compound of formula (I) which is formic acid.
  • the invention further provides the use of a catalyst of the invention as defined hereinbefore for the electro-oxidation of formic acid. Typically, said electro-oxidation proceeds in accordance with the following reaction:
  • the electrode comprises the catalyst of the invention. More typically, the electrode comprises a conducting substrate and a catalyst of the invention as defined hereinbefore.
  • said electro-oxidation proceeds in accordance with the following reaction:
  • the invention further provides the use of a catalyst of the invention as defined hereinbefore in a fuel cell.
  • the fuel cell comprises a compound of formula (I), (II), (III) or (IV) as defined hereinbefore.
  • the invention further provides the use of a catalyst of the invention as defined hereinbefore for the electro-oxidation of a compound of formula (I), (II), (III) or (IV) as defined hereinbefore in a fuel cell.
  • a catalyst of the invention as defined hereinbefore, for the electro-oxidation of formic acid in a direct formic acid fuel cell.
  • the invention further provides an electrode suitable for use in a fuel cell, which electrode comprises a catalyst of the invention as defined hereinbefore.
  • the electrode comprises a conducting substrate and a catalyst of the invention as defined hereinbefore.
  • the invention further provides a fuel cell which comprises: a catalyst of the invention as defined hereinbefore, or an electrode of the invention as defined above.
  • the fuel cell is a direct formic acid fuel cell.
  • Hydrogen tetrachloroaurate (III) (HAuCl 4 , 52 %), silver nitrate (99%), ethylene glycol 99%, diethylene glycol 99%, polyvinyl pyrrolidone) (PVP, MW 40,000), 98% polyvinyl alcohol) (PVA, MW 13,000- 23,000), 80% hydrolysed polyvinyl alcohol) (PVA, MW 9000-10000), H 13 COOH (95% weight in H 2 0, 99 atom % 13 C), sulphuric acid (97.5%, analytical grade), perchloric acid (70%) and absolute ethanol were purchased from Aldrich.
  • Poly(ethylenimine) (branched PEI, MW 10,000), acetone (laboratory reagent grade), nitric acid (70%, analytical grade), sodium hydrogen carbonate were obtained from Fischer. Triethylene glycol (99%), formic acid puriss (-98%) were procured from Fluka. .
  • Perfluorosulfuric acid PTFE copolymer 5% w/w solution was purchased from Alfa Aesar.
  • Vulcan ® carbon XC 72R was obtained from Cabot Company Limited.
  • 1% CO in helium gas was purchased from BOC gases.
  • Synthesis of polymer stabilised metal nanoparticles was carried out by the polyol process using PVP as a main stabiliser and polyol such as ethylene glycol, diethylene glycol, triethylene glycol as both solvent and reducing agent.
  • the size of nanoparticles was controlled by using various reaction parameters such as reaction temperature, reaction time, polyol type, concentration of metal salt and mole ratio of stabiliser to metal salt.
  • PVP-Pd nanoparticles In a 100 mL round bottom flask, 0.0560g of Pd(N0 3 ) 2
  • PVA-Pd and PEI-Pd nanoparticles The method for the synthesis of PVA-Pd and PEI- Pd nanoparticles were the same as those described for PVP-Pd nanoparticles except that the polymer (PVA 0.1 g or PEI 0.4g) and ethylene glycol were heated to 120 °C for 30 min before the addition of Pd(N0 3 ) 2 .
  • Polymer stabilized Pd nanoparticles in colloidal form were prepared by using a water soluble polymer, Polyvinyl pyrrolidone) (PVP), 98% Poly(vinyl alcohol) (98% PVA), 80% hydrolyzed poly( vinyl alcohol) (80% PVA), or hyper-branched Poly(ethylenimine) (HB-PEI).
  • PVP Polyvinyl pyrrolidone
  • HB-PEI hyper-branched Poly(ethylenimine)
  • reaction parameters are controlled; ratio of polymer-stabiliser to Pd(II) ion is 10 times, reaction time is 2 hr, heating rate is 7°C/min. Reaction temperature is 160 °C. Concentration of Pd ion is 7.1 mM.
  • solubility of polymer in polyol media affects the stability of the polymer stabilised nanoparticles.
  • PVP with amide group can be well dissolved in ethylene glycol in homogeneous solution at room temperature while HB-PEI and 80% PVA are partially soluble.
  • PVA with high degree of hydrolysis (98%) is only dissolved in ethylene glycol at temperature above 80°C.
  • Polarity of polymer After the reduction reaction, Pd nanoparticles stabilised by PVP and 80%PVA are in suspension form while Pd stabilised by HB-PEI and 98% PVA are precipitated from the reaction.
  • the stabilisation of metal particles by polymers strongly depends on the extent of solvation of the polymer in the surrounding medium (ethylene glycol). Therefore, in order to stabilise nanoparticles, polymers should typically not only dissolve in a solvent but also have more polarity than solvent.
  • ethylene glycol acts as solvent and reducing agent.
  • the amide group of PVP and acetyl group of 80% hydrolysed PVA have a higher polarity than the hydroxyl group and the oxidized forms of ethylene glycol whereas the amine group in HB-PEI and the hydroxyl group in 98% PVA have a lower polarity.
  • a higher polarity increases the interactions between the functional groups of the polymer and the metal causing of the precipitation of metal nanoparticles.
  • the solvent used in the reaction medium is therefore an important factor.
  • the selected solvent should be a good solvent for the metal salt and the polymer.
  • the optimum solvent system should have lower polarity than the most polar constituent of the polymer, and the polymer must coordinate to the nanoparticle's surface to be an effective stabilizer.
  • PVP-Ru nanoparticles of various sizes were synthesized according to the following procedure.
  • 0.0520g (2.0652 1 ⁇ - 4 moles) of RuCl 3 xH 2 0 and 0.24 g (2.1628 ⁇ 10 '3 moles) of PVP were dissolved in 30 mL of diethylene glycol under stirring.
  • the solution was then heated (7 °C/min) to 160°C under N 2 atmosphere. After 2 hrs at 160 °C, a dark brown solution of colloidal PVP-Ru nanoparticles was obtained.
  • the PVP-Ru nanoparticles were precipitated in acetone, washed with acetone twice and dried under N 2 atmosphere.
  • PVP-Ru nanoparticles obtained by this method were 2.3 nm.
  • Different sizes of PVP-Ru nanoparticles were synthesized by varying the mole ratio of PVP to Ru 3+ ion, reaction temperature, heating rate and polyols.
  • the list of experiments with various reaction parameters along with particle size achieved are presented below.
  • suitable and effective methods of controlling the metal particle size were studied. This research examined a number of variables and parameters affecting the characteristics of the Ru nanoparticles. These include reaction conditions such as reaction temperature, time, heating rate, the polymer to metal ratios and various reducing agents. It was found that these parameters mainly affect the particle size of the colloidal Ru nanoparticles and its distribution within the polymer, as shown in Table 2.
  • Size, shape and distribution of nanoparticles can be characterized by transmission electron microscope.
  • TEM images of PVP-Ru nanoparticles are shown in Fig 2. Standard deviations were calculated from the distribution of particle size about 100 particles. The standard deviation is less than 0.3 for all the reactions carried out under various parameters. It is indicated that mono-dispersed PVP-Ru nanoparticles were obtained by this preparation method
  • Pd nanoparticles were synthesized by step growth using pre-formed PVP-Pd nanoparticles as seed.
  • the first step growth of PVP-Pd nanoparticles was carried out by mixing 10 mL of colloidal PVP-Pd nanoparticles with a solution containing 0.056g (2.1417x 1 ⁇ "4 moles) of Pd(N0 3 ) 2 , 0.24g of PVP and 30 mL of diethylene glycol, followed by heating the mixture at 90°C for 2 hrs.
  • the second step growth was conducted in the same way.
  • PVP-Pd nanoparticles' sizes in range 2.3-5.2 nm were prepared by polyol process using Pd(NO) 3 as CI " free precursor and PVP as stabilizer.
  • PVP-Pd nanoparticles size of 2.7 nm were used as the seed for stepwise growth reduction in order to obtain the larger particles with a small change of size distribution as shown in Table 3.
  • the TEM images of PVP-Pd nanoparticles are shown in Fig 4. Table 3: Sizes and distribution of PVP-Pd nanoparticles prepared by step growth formation
  • Monodispersed PVP-Pt nanoparticles were prepared by polyol process. 3 ⁇ 4PtCl 6 as precursor for Pd(IV) was reduced at different temperature and heating rate for 2 hr. In ethylene glycol, the Pt(IV) ion can be reduced at a wider range of temperature (110-180°C) than in alcohol. At these reduction temperatures, near spherical shape of Pt particles were obtained with narrowed-size distribution as shown in Table 4 and Fig 5. It can be seen that the obtained particle sizes of Pt particles strongly depend on the heating rate of reaction mixture as the nucleation and growth step are mainly depending on reduction rate during the particle formation period.
  • the reaction time is 2 hr.
  • Mole ratio of PVP to Pt ion is 10.
  • Solvent is ethylene glycol.
  • Nanoparticles In a 100 mL round bottom flask, 0.025g (2.4270x 10 "4 moles) of Rh(N0 3 ) 3 was dissolved in 300 ⁇ 1 of water and then 0.24 g (2.1628 l0 "3 moles) of PVP was added. The mixture was dissolved in 30 mL of ethylene glycol under stirring and heated (7°C/min) to 160°C under N 2 atmosphere. A dark brown of colloidal PVP-Rh nanoparticles was obtained after 2 hrs at 160 °C. The PVP-Rh nanoparticles were precipitated in acetone, washed with acetone twice and dried under N 2 atmosphere. The particle size of obtained PVP-Rh nanoparticles was 2.0 nm. The particle size of PVP-Rh nanoparticles was controlled by varying reaction temperature, heating rate and polyol solvent as shown in Table 5 below.
  • PVP-Rh nanoparticles were prepared from Rh(N0 3 ) 3 as precursor. Since this precursor gave a low solubility in the polyol solvent, it was then dissolved in a minimum amount of water before mixing with ethylene glycol. PVP-Rh nanoparticles sizes in range 2-10 nm were prepared by varying the reduction rate which strongly influence on controlling the particle size. The sizes of the obtained PVP-Rh nanoparticles are shown in Table 5. The size distribution was found to increase with an increase of particle size and the particle shape seems to change from cubo-octaheral to polyhedral when the particle size is increased. The TEM images of the obtained particles are shown in Fig 6.
  • PVP-Ag nanoparticles particle sizes in range 15-50 nm were prepared by the polyol process with different reaction conditions as shown in Table 6. TEM images of some sample are shown in Fig. 7.
  • Colloidal Au nanoparticles size in range 10-50 nm were prepared by polyol process using ethylene glycol as reducing agent.
  • the optimum condition for the preparation of nanosized Au particles with high dispersity was examined from change of various parameters. The results are shown in Table 7.
  • the TEM images of colloidal PVP-Au nanoparticle are shown in Fig 8.
  • the heating rate is controlled to 7°C/min.
  • Bimetallic nanoparticles were prepared by polyol process using PVP as stabilizer. Salts of two different metals were mixed together and simultaneously reduced to obtain bimetallic nanoparticles with alloy structure whereas core-shell structure was obtained by reduction of two different metal salts in two stages. The first stage involved the reduction of metal salt to form the metal core while the second stage involved the reduction of another metal salt on the surface of the metal core to form the shell.
  • the alloy bimetallic of Pt/Pd and Ag/Pd were prepared by continuous reduction.
  • core-shell structured nanoparticles having a Pd shell and a core of Pt, Ru, Rh or Ag were prepared by successive reduction.
  • the core-shell structured Au@Pd was prepared by co-reduction.
  • Nanoparticles of Ru, Pt, Rh and Ag metal cores were prepared first by following the procedure outlined in sections 1.2, 1.4, 1.5 and 1.6, respectively. Pd salts were then reduced in the presence of these metal cores to obtain bimetallic nanoparticles of various metal-cores with Pd-shell. A typical procedure for the synthesis of a polymer protected bimetallic nanoparticles with 1 : 1 mole ratio of metal-core Pd-shell is described here.
  • TEM images were recorded on JOEL 2000FX.
  • TEM samples were prepared by placing a drop of colloidal dispersion of metal nanoparticles in methanol onto a carbon-coated copper grid followed by natural evaporation of the solvent. At least 100 nanoparticles were considered for reporting the mean diameter with standard deviation.
  • Pt-Pd bimetallic 1 : 1 molar ratio was prepared as detailed above by co-reduction of Pd( 0 3 ) 2 and H 2 PtCl by polyol process in the presence of ethylene glycol as reducing agent and PVP as stabilizer. The mixture of the metal salts was reduced at 160°C with high heating rate (20°C/min). The TEM image of the obtained nanoparticles is shown in Fig 9 a).
  • Ag-Pd and Au-Pd bimetallic nanoparticles were also prepared by the same method as the Pt-Pd bimetallic nanoparticles, AgN0 3 and HAuCI 4 being used as the metal precursor respectively.
  • the TEM images of obtained nanoparticles are shown in Fig 9 b) and c). From the images in Fig 9, the obtained Pt-Pd, Ag-Pd and Au-Pd bimetallic nanoaprticles are stable (no aggregation). The results suggest these bimetallic nanoparticles are not mixtures of monometallics of both metals but consist of single bimetallic particles.
  • Pt-Pd and Ag-Pd bimetallic nanoparticles were also prepared by successive reduction as detailed above.
  • Pt and Ag nanoparticles were prepared as a core metal first follow by the reduction of Pd ion deposited on these metal cores.
  • the reduction temperature for the reduction of Pd shell is low at 90°C in order to avoid re-oxidation of core atom and the creation of new nuclei of Pd shell replacing deposit core surface.
  • the obtained bimetallic nanoparticles are uniform and have a narrow size distribution as shown in Fig 10.
  • the Pt-Pd bimetallic nanoparticles were prepared from 6.0 nm Pt cores and the Ag-Pd bimetallic nanoparticles were prepared from 15.0 nm Ag cores with the ratio of metal core to shell being 1 : 1. It can be seen from the TEM images in Fig. 10 a and b that the obtained bimetallic nanoparticles are larger than the metal core. The implication is that the Pt and Ag cores are covered by Pd atoms. Also, the difference in contrast between the core and shell metals is clearly observed in the larger bimetallic nanoparticles shown in Fig 10 c.
  • Rh-Pd and Ru-Pd bimetallic nanoparticles were also prepared by successive reduction. As the reduction potential of Rh and Ru are lower than Pd, Rh and Ru atom tend to segregate to the surface of particles during reduction. In order to obtain a Pd shell (reversed core- shell) a hydrogen sacrificial protective strategy was used to modify these nanoparticles.
  • Noble metals like Pd, Pt, and many others have the ability to adsorb hydrogen and split it to form metal-H bonds on the metal surface. Hydrogen atoms adsorbed on noble metals have a very strong reducing ability, implying a very low redox potential.
  • the hydrogen gas was passed through Rh and Ru monometallic colloidal nanoparticles at room temperature for 1 hr before mixing and reduction of the Pd presursor.
  • the TEM images of the obtained bimetallic nanoparticles are shown in Fig. 11. The images show very good dispersity of the particles.
  • UV-visible absorption spectra of Ag, Au and their bimetallic nanoparticles in aqueous solution were recorded at room temperature on Cintra 10 UV-Vis spectrometer using a quartz cuvette with an optical path length of 1 cm. Important information about the structure of nanoparticles such as alloy or core-shell structure is obtained by analysing the change of the position of plasmon absorption peak.
  • UV-visible spectra of Ag compared with Ag@Pd nanoparticle prepared at different molar ratios are shown in Fig. 12.
  • Ag nanoparticle has a characteristic surface plasmon resonance at 420 nm while Pd nanoparticle hasn't strong absorption and only shows a broad absorption tail (not shown).
  • Pretreatment of carbon lg of Vulcan ® XC-72R was pretreated with 60% nitric acid under reflux for 3 hrs. It was then filtered, washed with water until water washings neutral pH and dried overnight at 120°C.
  • Catalyst ink was prepared by ultrasonically dispersing 5.0 mg of M/C catalyst in a mixture of 200 ⁇ of ethanol and 50 ⁇ 1 of 5% w/w solution of perfluorosulfuric acid PTFE copolymer for 15 min.
  • Vulcan carbon has been thought to be one of the best candidate supports for electrocatalysts for PEMFCs due to its proper surface area and pore structure. Therefore, it was used as a catalyst supported for this study.
  • the as-prepared mono and bimetallic nanoparticles were loaded on Vulcan carbon with 20% metal loading by physical deposition.
  • the obtained metal/C supported nanoparticles were filtered and washed many times with water and ethanol to remove excess PVP stabilizer, polyol solvent and inorganic ion impurity.
  • TEM images of Pd/C are shown in Fig 14. The images clearly show that the obtained Pd/C nanoparticles are well dispersed and do not aggregate after deposition on the carbon support.
  • Electrochemical measurements were carried out on an electrochemical cell with conventional three electrode configuration.
  • the glassy carbon thin film electrode coated with the metal/C catalyst under investigation was used as working electrode.
  • the saturated calomel electrode (SCE) was used as the reference electrode.
  • a Pt disk electrode with Surface area 0.0314 cm 2 was used as the counter electrode. All potentials were recorded with respect to SCE.
  • the cell was filled with 0.5 M H2SO4 as an electrolyte and purged with N 2 to remove dissolved oxygen. All formic acid oxidation experiments were performed in 0.5M H2SO4 + 2.0 HCOOH solution. MilliQ water was used to prepare the solutions. Electrochemical experiments were performed on compactstat, Ivium electrochemical analysis instrument. 2.4 Electrochemical Pretreatment
  • Cyclic Voltammetry Measurements Cyclic voltammetry measurements for formic acid electro-oxidation were carried out at room temperature in 0.5 M H 2 S0 4 and 2 M aqueous solution of formic acid at potential range between -0.2 and 1.2 V vs SCE and at a potential sweep rate of 50 mV/s.
  • Core-shell Ag@Pd catalysts having different molar ratios of Ag to Pd were prepared and characterized as detailed in Example 1.
  • the chemical shifts of adsorbed formate species on different compositions of Ag to Pd are presented in Table 9.
  • the correlation between chemical shift of bridging formate and mole fraction of Pd overlayer in Ag@Pd core-shell is shown in Fig. 16.
  • the obtained Ag@Pd samples also showed an increase in lattice constant, which is indicative of surface expansion ( ⁇ 0.5-3%) compared to monometallic Pd.
  • an increase in expansion of Pd lattice was clearly observed. This could also lead to stronger adsorption of formate.
  • the adsorption strength of adsorbed formate on the catalysts was analysed by measuring the chemical shift; this indicated that charge transfer and lattice strain effects influence adsorption strength.
  • the chemical shift of adsorbed formate in bridging form varies with the mole fraction of Pd overlayer as shown in Fig 16.
  • the adsorbed formate exhibits a higher chemical shift than those of pure Pd in the 13 C NMR spectra.
  • the resonance for l3 C nuclei of adsorbed formate on Ag@Pd catalyst containing 0.33 mole fraction of Pd had almost a similar chemical shift value to that of monometallic Pd, while the resonances for adsorbed formate on Ag@Pd catalysts containing 0.50 and 0.66 mole ratio of Pd appeared further downfield (higher chemical shifts).
  • Ag@Pd nanoparticles were deposited on carbon support and the polymer stabilizer was burnt off before catalytic testing.
  • the electrochemical activity of Ag@Pd/C catalysts for formic acid oxidation was examined as a function of overlayer thickness over different mole fractions of Pd by using cyclic voltammetry.
  • the current densities achieved for Ag- core Pd-shell nanoparticles with different mole ratio of Ag:Pd are shown in Fig 17.
  • the catalytic activity of various Ag@Pd catalysts is presented in terms of their mass activity and specific activity (see Figs. 18 and 19, respectively).
  • the maximum mass activity and specific activity was achieved for Ag@Pd catalyst with 1 : 1 mole ratio, which is in a very good agreement with the results obtained from solution 13 C NMR spectroscopy as detailed above.
  • the mass activity of Ag@Pd was found to decrease with either increasing or decreasing mole ratio of Ag or Pd. If some of Ag atoms are exposed on the surface of the Ag@Pd catalysts with high mole ratio of Ag-core, the less active Ag atoms causes a decrease in the activity per gram of the catalyst. When the molar ratio of Pd increases above 1, the particle size of Ag@Pd catalyst become larger, thus, lowering the total surface area and lowering the mass activity of the catalyst.
  • the specific activity of a catalyst depends on its electrochemical surface area (ECSA).
  • ECSA electrochemical surface area
  • the change in ECSA of the catalysts with mole fraction of Pd overlayer in Ag@Pd catalysts is presented in Fig. 20. From Fig. 20 it is clear that the maximum ECSA was observed for Ag@Pd catalyst with 1:1 mole ratio. Both the specific activity (Fig 19) and ECS A (Fig 20) for Ag@Pd catalysts with various molar ratios of Ag:Pd exhibited the same trend.
  • the surface probing by solution C NMR spectroscopy for determination of adsorption strength of Ag@Pd catalysts can clearly reflect their electro-oxidation activities. Weaker adsorption of formate results in lower activity of the catalyst while stronger adsorption of formate results in higher activity.
  • the surface structure of the bimetallic catalysts was investigated by CO adsorption using ATR-IR spectroscopy.
  • the electronic properties of core-shell type catalysts were inferred by analysing the chemical shifts of adsorbed formate (i.e., to assess the adsorption strength for formate on various core-shell catalysts by solution 13 C NMR spectroscopy) and their catalytic activity for formic acid electro-oxidation was examined by electrochemical techniques.
  • Fig. 22(a) shows the relationship between C chemical shifts of three modes of adsorbed formates on Ag@Pd, Rh@Pd, Au@Pd, Ru@Pd and Pt@Pd bimetallics and work functions of Ag, Rh, Au, Ru, Pd and Pt from (111) fee lattice plane are used while (001) of hep Ru with identical surface feature is used.
  • Work function is the minimuim energy needed to remove an electron from the Fermi level. In chemical language, it is similar to the ionization potential (binding energy) that reflects the energy state of electrons on solid. It is clear from Fig.
  • the charge transfer between metal-core and metal-shell is related to the work function and the work function in turn is related to the adsorption strength.
  • work function is determined by surface orientation and surface charge redistribution. Charge transfer can determine the sign and magnitude of surface dipole change leading to a strong dependence on the orientation of the substrate. Therefore, the work function is governed by the details of the charge redistribution. Charge redistribution is a factor which contributes to the shift of d-band of Pd-shell. Therefore, the data on work-function anisotropy obtained from the (1 1 1 ) crystal plane of fee structure of Pt, Pd, Rh, Ag and Au metals were used for the plot as shown in Fig.
  • FIG. 22(b) A plot of specific activity against the chemical shift of adsorbed formate for different monometallic and Metal-core Pd-shell bimetallic catalysts is shown in Fig. 22(b). The maximum mass activity for formic acid electro-oxidation was observed for the
  • nanocatalyst based on Ag-core Pd-shell structure nanocatalyst based on Ag-core Pd-shell structure.
  • Formic acid is nontoxic and a liquid at room temperature with a density of 1.22 g. mL "3 and it can be safely handled in aqueous solution.
  • the present work shows for the first time that solid Ag-Pd core-shell nano-catalysts can rapidly decompose HCOOH in water to form H 2 and C0 2 (1 : 1) gas mixture with CO concentration of lower than 10 ppm at room temperature (20°C).
  • a turnover frequency (TOF) per surface metal site of around 88 h "1 is estimated, giving a large amount of hydrogen gas (2.8L.g "1 .h '1 ) at ambient conditions with no additive(s) required.
  • Figure 23(a) shows the rates of formic acid decomposition in water over different metal colloids at room temperature. As seen from the figure, the rate of formic acid
  • transition metal nanoparticles can help to catalyse formic acid decomposition in water.
  • This catalyst also gives the highest activity for formic acid decomposition to CO and H 2 at room temperature.
  • the surface modification of Ag-core with different molar ratios of Pd overlayer has brought changes in the chemical shift of adsorbed formate, as shown in Fig.25(a).
  • the resonances for different molar ratios (3:1, 2: 1 and 1 : 1 Ag to Pd) were shifted to higher chemical shifts compared to that of adsorbed formate on monometallic Pd catalyst but the 1 :3 molar ratio gave a very similar value as the pure Pd.
  • the catalytic activity for formic acid decomposition of various Ag@Pd catalysts at different molar ratios is presented in Fig. 25(b).
  • the highest activity was achieved for Ag@Pd catalyst with 1 : 1 molar ratio, which is in very good agreement with the highest chemical shift values observed from solution C NMR spectroscopy.
  • the activity of Ag@Pd was found to decrease with either increasing or decreasing mole ratio of Ag or Pd. If some of Ag atoms are exposed on the surface of the Ag@Pd catalyst when a high molar ratio of the Ag-core is used, the relatively inactive Ag atoms can cause a decrease in catalyst activity. On the other hand, too thick a Pd shell can also decrease catalytic activity, which is presumably influenced by the lower degree of electronic perturbation from the Ag inner core.
  • Turnover number (TON) is defined as (number of moles of formic acid converted to H 2 /C0 2 )/(number of mole of catalyst) for 3.5 h reaction.
  • the estimated surface area of 80m g ' of this catalyst was obtained by the electrochemical surface area technique (ECSA).
  • ECSA electrochemical surface area technique

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Abstract

L'invention concerne un procédé de fabrication de H2 à partir d'un composé de formule (I), (II), (III) or (IV) : R1COOH (I); R2OH (II); R3CHO (III); R4NH2 (IV), où R1 représente H ou alkyle en C1-10 non substitué ou substitué; R2 représente alkyle en C1-10 non substitué ou substitué; R3 représente H ou alkyle en C1-10 non substitué ou substitué; R4 représente H, alkyle en C1-10 non substitué ou substitué ou C(O)NR5R6; et R5 et R6, qui sont identiques ou différents, sont indépendamment choisis parmi H et alkyle en C1-10 non substitué ou substitué. Ce procédé comprend la mise en contact d'une phase liquide qui comprend ledit composé de formule (I), (II), (III) ou (IV) avec un catalyseur, lequel catalyseur comprend : (a) des nanoparticules polymétalliques, dont chacune comprend un premier métal et un second métal, lequel premier métal est choisi parmi un métal du bloc d du Groupe (9), Groupe (10), Groupe (11) ou Groupe (12), et lequel second métal est autre que ledit premier métal, les particules polymétalliques comprenant un cœur qui comprend ledit second métal et une écorce entourant ledit cœur, ladite écorce comprenant ledit premier métal; ou (b) des nanoparticules qui comprennent un métal choisi parmi le palladium, le rhodium, le ruthénium, l'iridium, le cuivre et l'argent, et qui ont une dimension moyenne de particule de moins de ou égale à 50 nm, à la condition que, lorsque ledit composé est un composé de formule (II), le catalyseur comprend (a) lesdites nanoparticules polymétalliques. L'invention porte également sur un catalyseur pour la production d'hydrogène à partir d'un composé de formule (I)-(IV) ou pour l'électro-oxydation d'un composé de formule (I)-(IV), lequel catalyseur comprend des nanoparticules polymétalliques, lesquelles nanoparticules polymétalliques comprennent un cœur et une écorce entourant le cœur, l'écorce comprenant un premier métal qui est le palladium, et le cœur comprenant un second métal, le second métal étant autre que le palladium, le platine, l'or, le fer, le cobalt, le nickel, le titane, le tungstène, le tantale, le vanadium et le niobium. L'invention porte également sur un procédé de fabrication des catalyseurs de l'invention, et les utilisations suivantes des catalyseurs de l'invention : utilisation pour l'électro-oxydation d'un composé de formule (I)-(IV); utilisation pour l'électro-oxydation d'acide formique; utilisation dans une pile à combustible; utilisation pour l'électro-oxydation d'un composé de formule (I)-(IV) dans une pile à combustible; et utilisation pour l'électro-oxydation d'acide formique dans une pile à combustible à acide formique direct. L'invention porte également sur une électrode appropriée pour être utilisée dans une pile à combustible, comprenant un catalyseur de l'invention, et sur une pile à combustible comprenant un catalyseur ou une électrode de l'invention. L'invention porte aussi sur un procédé pour l'électro-oxydation d'un composé de formule (I)-(IV) avec un catalyseur de l'invention.
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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015003680A1 (fr) 2013-07-09 2015-01-15 Universität Zu Köln Traitement des eaux usées et production d'hydrogène
WO2015187100A1 (fr) * 2014-06-05 2015-12-10 Agency For Science, Technology And Research Electrocatalyseur pour la production d'hydrogène
WO2016073827A1 (fr) * 2014-11-06 2016-05-12 The University Of North Carolina At Chapel Hill Cellules de photo-électrosynthèse à colorant à haut rendement
WO2016136939A1 (fr) * 2015-02-28 2016-09-01 株式会社フルヤ金属 Procédé de production d'un catalyseur supporté exempt de matériaux polymères protecteurs
JP2017000948A (ja) * 2015-06-09 2017-01-05 国立大学法人大阪大学 コア−シェル触媒およびこれを利用したアルケンの製造方法
JP2018118877A (ja) * 2017-01-25 2018-08-02 飯田グループホールディングス株式会社 水素供給システムおよび水素供給方法
CN111354953A (zh) * 2018-12-20 2020-06-30 现代自动车株式会社 一种制备无碳载体的燃料电池的催化剂的方法
CN113042069A (zh) * 2021-03-31 2021-06-29 泉州师范学院 一种甲酸还原的钯铜纳米催化剂的合成方法与应用
CN113413922A (zh) * 2021-07-19 2021-09-21 中国科学院成都有机化学有限公司 一种用于甲酸液相分解制氢的多相催化剂及其制备方法

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5082187B2 (ja) * 2003-10-06 2012-11-28 日産自動車株式会社 固体高分子型燃料電池用電極触媒粒子の製造方法
US7704919B2 (en) * 2005-08-01 2010-04-27 Brookhaven Science Associates, Llc Electrocatalysts having gold monolayers on platinum nanoparticle cores, and uses thereof
WO2009135189A1 (fr) * 2008-05-01 2009-11-05 Monsanto Technology Llc Utilisation de métal dans des catalyseurs supportés de piles à combustible contenant du métal
DE102008050577A1 (de) * 2008-10-06 2010-04-08 RUHR-UNIVERSITäT BOCHUM Verfahren zur Herstellung von Kern-Schale-Katalysatoren und Elektrode daraus
JP5482095B2 (ja) * 2008-10-30 2014-04-23 ソニー株式会社 白金含有触媒を含有する電極及びその製造方法、並びに、電気化学デバイス

Non-Patent Citations (10)

* Cited by examiner, † Cited by third party
Title
ANGEW. CHEM. INT. ED., vol. 47, 2008, pages 3962 - 3965
ANGEW. CHEM. INT. ED., vol. 47, 2008, pages 3966 - 3968
ANGEW. CHEM., vol. 120, 2008, pages 4026 - 4029
ANGEW. CHEM., vol. 120, 2008, pages 4030 - 4032
CHEM. EUR. J., vol. 15, 2009, pages 3752 - 3760
CHEMSUSCHEM, vol. 1, 2008, pages 751 - 758
CHEMSUSCHEM, vol. 3, 2010, pages 71 - 74
OJEDA, IGLESIA, ANGEW. CHEM. INT. ED., vol. 48, 2009, pages 4800 - 4803
YOSHIDA, Y. UEDA, S. OTSUKA, J. AM. CHEM. SOC., vol. 100, 1978, pages 3941 - 3942
ZHOU, W. J., LEE, J. Y., ELECTROCHEM. COMMUN., vol. 9, 2007, pages 1725 - 1729

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015003680A1 (fr) 2013-07-09 2015-01-15 Universität Zu Köln Traitement des eaux usées et production d'hydrogène
DE102013011379A1 (de) * 2013-07-09 2015-01-15 Universität Zu Köln H2-Produktion
DE102013011379B4 (de) * 2013-07-09 2018-10-25 Martin Prechtl H2-Produktion
WO2015187100A1 (fr) * 2014-06-05 2015-12-10 Agency For Science, Technology And Research Electrocatalyseur pour la production d'hydrogène
WO2016073827A1 (fr) * 2014-11-06 2016-05-12 The University Of North Carolina At Chapel Hill Cellules de photo-électrosynthèse à colorant à haut rendement
WO2016136939A1 (fr) * 2015-02-28 2016-09-01 株式会社フルヤ金属 Procédé de production d'un catalyseur supporté exempt de matériaux polymères protecteurs
JPWO2016136939A1 (ja) * 2015-02-28 2017-12-07 株式会社フルヤ金属 高分子保護材フリー担持触媒の製造方法
JP2017000948A (ja) * 2015-06-09 2017-01-05 国立大学法人大阪大学 コア−シェル触媒およびこれを利用したアルケンの製造方法
JP2018118877A (ja) * 2017-01-25 2018-08-02 飯田グループホールディングス株式会社 水素供給システムおよび水素供給方法
CN111354953A (zh) * 2018-12-20 2020-06-30 现代自动车株式会社 一种制备无碳载体的燃料电池的催化剂的方法
CN113042069A (zh) * 2021-03-31 2021-06-29 泉州师范学院 一种甲酸还原的钯铜纳米催化剂的合成方法与应用
CN113413922A (zh) * 2021-07-19 2021-09-21 中国科学院成都有机化学有限公司 一种用于甲酸液相分解制氢的多相催化剂及其制备方法

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