WO2012018818A1 - Macrocycle modified ag nanoparticulate catalysts with variable oxygen reduction activity in alkaline media - Google Patents
Macrocycle modified ag nanoparticulate catalysts with variable oxygen reduction activity in alkaline media Download PDFInfo
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- WO2012018818A1 WO2012018818A1 PCT/US2011/046271 US2011046271W WO2012018818A1 WO 2012018818 A1 WO2012018818 A1 WO 2012018818A1 US 2011046271 W US2011046271 W US 2011046271W WO 2012018818 A1 WO2012018818 A1 WO 2012018818A1
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- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 title claims abstract description 31
- 239000001301 oxygen Substances 0.000 title claims abstract description 31
- 229910052760 oxygen Inorganic materials 0.000 title claims abstract description 31
- 239000003054 catalyst Substances 0.000 title claims description 95
- 150000002678 macrocyclic compounds Chemical class 0.000 title claims description 7
- 230000010757 Reduction Activity Effects 0.000 title description 2
- 239000002105 nanoparticle Substances 0.000 claims abstract description 40
- 239000000203 mixture Substances 0.000 claims abstract description 22
- 229910052709 silver Inorganic materials 0.000 claims abstract description 21
- 238000006722 reduction reaction Methods 0.000 claims abstract description 18
- 229910052723 transition metal Inorganic materials 0.000 claims abstract description 16
- -1 transition-metal macrocycles Chemical class 0.000 claims abstract description 15
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 14
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 13
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 9
- 238000006479 redox reaction Methods 0.000 claims description 50
- 229910052799 carbon Inorganic materials 0.000 claims description 26
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 18
- 229910052742 iron Inorganic materials 0.000 claims description 9
- 238000000034 method Methods 0.000 claims description 9
- 239000002245 particle Substances 0.000 claims description 8
- 150000004032 porphyrins Chemical class 0.000 claims description 8
- 239000006229 carbon black Substances 0.000 claims description 7
- 150000001875 compounds Chemical class 0.000 claims description 6
- XMWRBQBLMFGWIX-UHFFFAOYSA-N C60 fullerene Chemical class C12=C3C(C4=C56)=C7C8=C5C5=C9C%10=C6C6=C4C1=C1C4=C6C6=C%10C%10=C9C9=C%11C5=C8C5=C8C7=C3C3=C7C2=C1C1=C2C4=C6C4=C%10C6=C9C9=C%11C5=C5C8=C3C3=C7C1=C1C2=C4C6=C2C9=C5C3=C12 XMWRBQBLMFGWIX-UHFFFAOYSA-N 0.000 claims description 3
- 239000002134 carbon nanofiber Substances 0.000 claims description 3
- 239000002041 carbon nanotube Substances 0.000 claims description 3
- 229910021393 carbon nanotube Inorganic materials 0.000 claims description 3
- 229910003472 fullerene Inorganic materials 0.000 claims description 3
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical class C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 3
- 238000006243 chemical reaction Methods 0.000 claims description 2
- 238000004381 surface treatment Methods 0.000 claims description 2
- 239000010944 silver (metal) Substances 0.000 description 80
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 48
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Substances [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 31
- 239000000243 solution Substances 0.000 description 18
- 229910052751 metal Inorganic materials 0.000 description 16
- 239000002184 metal Substances 0.000 description 15
- 230000000694 effects Effects 0.000 description 14
- 238000005516 engineering process Methods 0.000 description 13
- 239000000446 fuel Substances 0.000 description 13
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 12
- 238000004833 X-ray photoelectron spectroscopy Methods 0.000 description 11
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 10
- 230000010287 polarization Effects 0.000 description 9
- 230000037361 pathway Effects 0.000 description 8
- 230000009467 reduction Effects 0.000 description 8
- 229920006395 saturated elastomer Polymers 0.000 description 8
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 7
- 239000000758 substrate Substances 0.000 description 7
- 230000003197 catalytic effect Effects 0.000 description 6
- 238000001179 sorption measurement Methods 0.000 description 6
- 125000004429 atom Chemical group 0.000 description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 5
- 239000011572 manganese Substances 0.000 description 5
- 230000004048 modification Effects 0.000 description 5
- 238000012986 modification Methods 0.000 description 5
- 239000011865 Pt-based catalyst Substances 0.000 description 4
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 4
- 238000002848 electrochemical method Methods 0.000 description 4
- 239000003792 electrolyte Substances 0.000 description 4
- AMWRITDGCCNYAT-UHFFFAOYSA-L hydroxy(oxo)manganese;manganese Chemical compound [Mn].O[Mn]=O.O[Mn]=O AMWRITDGCCNYAT-UHFFFAOYSA-L 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 229910044991 metal oxide Inorganic materials 0.000 description 4
- 238000002156 mixing Methods 0.000 description 4
- KDLHZDBZIXYQEI-UHFFFAOYSA-N palladium Substances [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 4
- 229910052763 palladium Inorganic materials 0.000 description 4
- IEQIEDJGQAUEQZ-UHFFFAOYSA-N phthalocyanine Chemical compound N1C(N=C2C3=CC=CC=C3C(N=C3C4=CC=CC=C4C(=N4)N3)=N2)=C(C=CC=C2)C2=C1N=C1C2=CC=CC=C2C4=N1 IEQIEDJGQAUEQZ-UHFFFAOYSA-N 0.000 description 4
- 229910052697 platinum Inorganic materials 0.000 description 4
- 230000027756 respiratory electron transport chain Effects 0.000 description 4
- 239000004332 silver Substances 0.000 description 4
- 239000013522 chelant Substances 0.000 description 3
- 229910052804 chromium Inorganic materials 0.000 description 3
- 229910052802 copper Inorganic materials 0.000 description 3
- 125000004122 cyclic group Chemical group 0.000 description 3
- 230000002349 favourable effect Effects 0.000 description 3
- 125000001153 fluoro group Chemical group F* 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 150000004706 metal oxides Chemical class 0.000 description 3
- 150000002739 metals Chemical class 0.000 description 3
- 238000001228 spectrum Methods 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- 229910052718 tin Inorganic materials 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 229910052725 zinc Inorganic materials 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 238000003775 Density Functional Theory Methods 0.000 description 2
- OAKJQQAXSVQMHS-UHFFFAOYSA-N Hydrazine Chemical compound NN OAKJQQAXSVQMHS-UHFFFAOYSA-N 0.000 description 2
- 229920000557 Nafion® Polymers 0.000 description 2
- 239000003011 anion exchange membrane Substances 0.000 description 2
- 238000012512 characterization method Methods 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 239000010941 cobalt Substances 0.000 description 2
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 2
- MPMSMUBQXQALQI-UHFFFAOYSA-N cobalt phthalocyanine Chemical compound [Co+2].C12=CC=CC=C2C(N=C2[N-]C(C3=CC=CC=C32)=N2)=NC1=NC([C]1C=CC=CC1=1)=NC=1N=C1[C]3C=CC=CC3=C2[N-]1 MPMSMUBQXQALQI-UHFFFAOYSA-N 0.000 description 2
- 239000000084 colloidal system Substances 0.000 description 2
- 238000002484 cyclic voltammetry Methods 0.000 description 2
- 239000010411 electrocatalyst Substances 0.000 description 2
- 229910021397 glassy carbon Inorganic materials 0.000 description 2
- 229910052737 gold Inorganic materials 0.000 description 2
- 239000010931 gold Substances 0.000 description 2
- 125000004435 hydrogen atom Chemical class [H]* 0.000 description 2
- 230000003993 interaction Effects 0.000 description 2
- 229910052741 iridium Inorganic materials 0.000 description 2
- 239000003446 ligand Substances 0.000 description 2
- 238000011068 loading method Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000012528 membrane Substances 0.000 description 2
- 239000003863 metallic catalyst Substances 0.000 description 2
- 238000001478 photoelectron diffraction Methods 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 239000000725 suspension Substances 0.000 description 2
- 229910052720 vanadium Inorganic materials 0.000 description 2
- 229910052726 zirconium Inorganic materials 0.000 description 2
- ZCAPDAJQDNCVAE-UHFFFAOYSA-N 5,6,7,8,14,15,16,17,23,24,25,26,32,33,34,35-hexadecafluoro-2,11,20,29,37,38,39,40-octazanonacyclo[28.6.1.13,10.112,19.121,28.04,9.013,18.022,27.031,36]tetraconta-1,3,5,7,9,11,13(18),14,16,19,21(38),22(27),23,25,28,30(37),31(36),32,34-nonadecaene Chemical compound C12=C(F)C(F)=C(F)C(F)=C2C(N=C2NC(C3=C(F)C(F)=C(F)C(F)=C32)=N2)=NC1=NC([C]1C(F)=C(F)C(F)=C(F)C1=1)=NC=1N=C1[C]3C(F)=C(F)C(F)=C(F)C3=C2N1 ZCAPDAJQDNCVAE-UHFFFAOYSA-N 0.000 description 1
- 229910018089 Al Ka Inorganic materials 0.000 description 1
- 229910020676 Co—N Inorganic materials 0.000 description 1
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- WQZGKKKJIJFFOK-GASJEMHNSA-N Glucose Natural products OC[C@H]1OC(O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-GASJEMHNSA-N 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000012670 alkaline solution Substances 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 230000003466 anti-cipated effect Effects 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 125000003118 aryl group Chemical group 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 229910002090 carbon oxide Inorganic materials 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- 229910000428 cobalt oxide Inorganic materials 0.000 description 1
- LBFUKZWYPLNNJC-UHFFFAOYSA-N cobalt(ii,iii) oxide Chemical compound [Co]=O.O=[Co]O[Co]=O LBFUKZWYPLNNJC-UHFFFAOYSA-N 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000005518 electrochemistry Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 238000007306 functionalization reaction Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 239000008103 glucose Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 238000003384 imaging method Methods 0.000 description 1
- 230000003116 impacting effect Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 229920002521 macromolecule Polymers 0.000 description 1
- 239000011943 nanocatalyst Substances 0.000 description 1
- 125000004433 nitrogen atom Chemical group N* 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 125000001997 phenyl group Chemical group [H]C1=C([H])C([H])=C(*)C([H])=C1[H] 0.000 description 1
- 229920000128 polypyrrole Polymers 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 238000009790 rate-determining step (RDS) Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- SQGYOTSLMSWVJD-UHFFFAOYSA-N silver(I) nitrate Inorganic materials [Ag+].[O-]N(=O)=O SQGYOTSLMSWVJD-UHFFFAOYSA-N 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 239000012279 sodium borohydride Substances 0.000 description 1
- 229910000033 sodium borohydride Inorganic materials 0.000 description 1
- 239000001509 sodium citrate Substances 0.000 description 1
- NLJMYIDDQXHKNR-UHFFFAOYSA-K sodium citrate Chemical compound O.O.[Na+].[Na+].[Na+].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O NLJMYIDDQXHKNR-UHFFFAOYSA-K 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 150000003624 transition metals Chemical class 0.000 description 1
Classifications
-
- B01J35/23—
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
- B01J21/18—Carbon
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
- B01J23/48—Silver or gold
- B01J23/50—Silver
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
- B01J23/74—Iron group metals
- B01J23/75—Cobalt
-
- B01J35/19—
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M4/90—Selection of catalytic material
- H01M4/9008—Organic or organo-metallic compounds
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M4/90—Selection of catalytic material
- H01M4/9041—Metals or alloys
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M4/90—Selection of catalytic material
- H01M4/9075—Catalytic material supported on carriers, e.g. powder carriers
- H01M4/9083—Catalytic material supported on carriers, e.g. powder carriers on carbon or graphite
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2531/00—Additional information regarding catalytic systems classified in B01J31/00
- B01J2531/02—Compositional aspects of complexes used, e.g. polynuclearity
- B01J2531/0238—Complexes comprising multidentate ligands, i.e. more than 2 ionic or coordinative bonds from the central metal to the ligand, the latter having at least two donor atoms, e.g. N, O, S, P
- B01J2531/0241—Rigid ligands, e.g. extended sp2-carbon frameworks or geminal di- or trisubstitution
- B01J2531/025—Ligands with a porphyrin ring system or analogues thereof, e.g. phthalocyanines, corroles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2531/00—Additional information regarding catalytic systems classified in B01J31/00
- B01J2531/80—Complexes comprising metals of Group VIII as the central metal
- B01J2531/84—Metals of the iron group
- B01J2531/845—Cobalt
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
- B01J31/16—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes
- B01J31/1616—Coordination complexes, e.g. organometallic complexes, immobilised on an inorganic support, e.g. ship-in-a-bottle type 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 novel technology relates generally to the field of electrochemistry, and, more particularly, to cobalt phthalocyanine and/or N4 macrocycle promoted Ag- based nano-metallic oxidation reduction reaction (ORR] catalysts.
- ORR nano-metallic oxidation reduction reaction
- Fuel cells typically employ a catalyst system for the oxygen electrode or air electrode to catalyze the ORR of the electrochemical device in alkaline media.
- Electrochemical devices include metal-air or sugar-air cells or batteries, and fuel cells such as H 2 /O 2 fuel cells or direct alcohol fuel cells.
- non-Pt catalysts including Ag, Au, Pd, Ni, manganese oxide, prophyrins, and phthalocyanines, are active and affordable for the ORR in alkaline media.
- the relatively inexpensive and abundant Ag is a top candidate to replace Pt for the ORR in alkaline media due to its relative high activity for the ORR through an approximated 4-electron pathway.
- the present novel technology relates to hybrid electrocatalytic systems including metallic nanoparticles incorporating transition-metal macrocycles exterior coatings or sheathes for catalyzing oxygen reduction reaction (ORR] in alkaline media, such as Ag nanopartiocles modified with a Co-based phthalocyanine surface treatment, for oxygen reduction reaction (ORR] in alkaline media.
- ORR oxygen reduction reaction
- One object of the present novel technology is to provide an improved catalyst for oxygen reduction reactions. Related objects and advantages of the present novel technology will be apparent from the following description.
- FIG. 1A graphically illustrates the molecular structure of CoPc.
- FIG. IB graphically illustrates the molecular structure of CoPcFi 6 .
- FIG. 1C graphically illustrates the Mulliken charge of FIG. 1A.
- FIG. ID graphically illustrates the Mulliken charge of FIG. IB.
- FIG. 2A shows the XPS narrow scan spectra of Co2p3/2 core level for Ag/C, CoPc@Ag/C, CoPcFi6@Ag/C, CoPc/C and CoPcFi 6 /C catalysts.
- FIG. 2B shows the XPS narrow scan spectra of Ag3ds/2 for Ag/C
- FIG. 3 shows the ORR polarization curves obtained on CoPc/C, CoPcFi6/C,
- FIG. 4 presents the mass-corrected Tafel plots of log Ik (mA cm 2 ) vs. the electrode potential E (vs. Hg/HgO] for the ORR on the electrodes prepared with various catalysts in an 02-saturated 0.1 M NaOH solution.
- FIG. 5 graphically illustrates current density vs. potential for CoPc/C, CoPcFie/C, Ag/C, CoPc@Ag/C, CoPcFi 6 @Ag/C, and Pt/C, respectively.
- FIG. 6A graphically illustrates a comparison of cyclic voltammetris of different catalysts in Ar-purged 0.1 M NaOH solution at 5 th cycle, CoPc and CoPcFi 6 .
- FIG. 6B graphically illustrates a comparison of cyclic voltammetris of different catalysts in Ar-purged 0.1 M NaOH solution at 5 th cycle,Ag/C, CoPc@Ag/C and CoPcFi 6 @Ag/C.
- FIG. 6C graphically illustrates a comparison of cyclic voltammetris at first cycle at CoPc@Ag/C and CoPcFi 6 @Ag/C.
- FIG. 7A-7F graphically illustrate the oxygen reduction polarization curves at 400,900, 1600 and 2500 rpm in 0 2 -purged 0.1 M NaOH.
- FIG.8 graphically illustrates Levich plots of (3 ⁇ 4 reduction on Ag/C
- CoPc@Ag/C, CoPcF 16 @Ag/C, CoPc/C, CoPcF 16 /C and Pt/C catalysts
- AEMFCs anion exchange membrane fuel cells
- ORRs oxygen reduction reactions
- PEMFCs proton exchange membrane fuel cells
- AFCs alkaline fuel cells
- non-Pt catalysts including Ag, Au, Pd, cobalt and manganese oxide, prophyrins, and
- phthalocyanines have been well studied.
- the relatively inexpensive and abundant Ag is an economically advantageous choice to replace Pt as the cathode catalyst for applying in AEMFCs.
- Ag has a relative high electrocatalytic activity for reducing O2 via an approximated 4-electron ORR pathway.
- ORR kinetics on Ag nano- particles in alkaline media are problematic, as ORR overpotentials on Ag catalysts are more than 100 mV higher than that on Pt catalysts under the same conditions.
- Adsorbed coordination compounds on metallic substrates show promise with respect to the controlled functionalization of surfaces on the nanoscale.
- Planar metal complexes such as M(II]-porphyrins (MP] and M(II ⁇ - phthalocyanines (MPc] are particularly interesting due to their physical and chemical properties.
- the metal centers of MP or MPc molecules typically possess no axial ligands and represent coordinatively unsaturated sites with potential catalytic functionality.
- CoPc and FePc molecules are well known to have desirable electrocatalytic activities for reducing O2 molecules.
- Co-tetraphenyl-porphyrin Co-tetraphenyl-porphyrin
- PED photoelectron diffraction
- NXAFS near-edge x-ray absorption fine-structure
- DFT discrete Fourier transform
- the present novel technology relates to hybrid catalysts, specifically hybrid electrocatalytic systems 100 incorporating metal chelate compounds or transition-metal macrocycles 105 with metallic or metal oxide nano-particles 110 for catalyzing oxygen reduction reaction (ORR] in alkaline media.
- Co-macrocycles 105 may include Co-phthalocyanines (CoPc],
- the transition-metal macrocycles 105 are typically large organic molecules containing transition-metals (Co, Fe, Mn, Ni, and the like], which are typically bonded with two or four nitrogen atoms.
- the large organic molecules are typically selected to be phthalocyanine, porphyrin, derives thereof, or the like.
- Metallic nanoparticles include Ag/Ag-based, Co/Co-based and other metal/metal-based particles.
- Metals in metallic nanoparticles 110 may be in various forms, such as metallic, alloyed with other metals, metal oxide, and etc.
- the metallic nanoparticles may include Ag, Pt, Pd, Ni, Co, Au, W, Mo, Mn, Fe, Ir, Sn, Cu, Zn, Os, Rh, Ru, Ti, V, Cr, Zr, Mo, their oxides, and combinations thereof.
- the particle size of metallic nanoparticles 110 is typically in the range of about 0.1 nm to about 5000 nm, more typically from about 1 nm to about 1000 nm.
- Metallic nanoparticles 110 may be supported on carbon, unsupported, or mixed with carbon or other electrically conducting or semiconducting material.
- Typical support structures include carbon black, carbon nanotubes, carbon nanofibers, fullerenes, and other carbon materials with different morphologies, or
- Macrocycles 105 can be physically mixed with carbon-supported or non- carbon supported metallic nanoparticles 110, or adsorbed physically or chemically on carbon-supported or non-carbon supported metallic nanoparticle 110 surfaces to form a hybrid catalyst system 100.
- transition-metal macrocycles 105 onto metallic nano-particles 110, physical and electrochemical properties of the surface of nano-metallic catalysts 100 can be modified significantly.
- coating Co-phthalocyanines (CoPc] 105 on carbon supported Ag or AgCo nano- particles 110 modifies both the electronic properties and geometrical structures of both metallic surfaces and CoPc surface, yielding improved oxygen and/or water adsorption and reducing OH- adsorption. Therefore, improved ORR activity and stability on the invented hybrid CoPc + Ag/Ag-based catalysts 100 are achieved.
- ORR activities on carbon supported Ag nano-particles 110 modified with CoPc or CoPcFie molecules 105 (CoPc@Ag/C and CoPcFi 6 @Ag/Q.
- CoPc@Ag/C or CoPcFi6@Ag/C catalysts lOOhave more favorable O2 reduction potentials and rate constants than CoPc/C (and the CoPcFi6/C] catalysts or Ag/C catalysts.
- the ORR activity of the Ag nano-catalysts 100 is variable or tunable by adjusting the compositions of the adsorbed organic molecules.
- a new class of "hybrid" catalysts 100 based on the adsorption of organic molecules 110 on metallic nano- particles 105 for meeting performance and durability requirements in fuel cell applications is thus developed.
- CoPc or CoPcFi6-modified Ag/C catalyst 110 were prepared by mixing 15 weight percent CoPc or 15 weight percent CoPcFi 6 with 85 weight percent (60 weight percent Ag/C] uniformly in ethanol by ultrasonic stirring, which were denoted as CoPc@Ag/C and CoPcFi6@Ag/C respectively.
- the CoPc@Ag/C and CoPcFi6@Ag/C samples could also be prepared by adsorbing CoPc directly onto the Ag/C electrodes from a DMF solution containing 10 -5 M CoPc.
- the geometrical and electronic structures of CoPc and CoPcFi 6 molecules were calculated using DFT Composition and electrochemical properties of the catalysts 100 were characterized by x-ray photoelectron spectroscopy (XPS], cyclic voltammetry (CV], rotating ring disk electrode (RRDE] and oxygen electrode tests.
- XPS x-ray photoelectron spectroscopy
- CV cyclic voltammetry
- RRDE rotating ring disk electrode
- a cathode for catalyzing ORRs in alkaline media may be produced comprising metal chelate compounds 105 and metallic and/or oxide
- nanoparticles 110 may be used to produce an anode for catalyzing hydrogen, hydrazine, alcohol, and/or glucose oxidation reactions in alkaline media.
- the metallic nanoparticles 110 may be sleected from the group including Ag, Pt, Pd, Ni, Co, Au, W, Mo, Mn, Fe, Ir, Sn, Cu, Zn, Os, Rh, Ru, Ti, V, Cr, Zr, Mo, their oxides, and combinations thereof.
- the metal chelate 105 may be selected from the group including Co, Fe, Ni, Mn, Zn, Cr, Cu, and/or Sn phthalocyanines, porphyrins, and their derivatives, with or without heat treatment and in concentrations of from about 1 ppm to about 80 weight percent of the catalyst material.
- the transition-metal macrocycles 105 and nanoparticles 110 may or may not be dispersed in carbon and/or metal oxide supports for electronic conductivit catalyst distribution, and stability purposes.
- anodes and cathodes prepared as described above may be used in the production of anion exchange membrane fuel cells or metal-air batteries.
- FIG. 1 shows the DFT optimized CoPc and CoPcFi 6 molecular structures, which are planar 4-fold symmetrical aromatic macrocyclic organic molecule.
- FIG. 2A illustrates the XPS narrow scan spectra of Co2p3/2 core level for Ag/C, CoPc@Ag/C, CoPcFi6@Ag/C, CoPc/C and CoPcFi 6 /C catalysts.
- a peak at 780.9 eV for CoPc/C and at 781.4 eV for CoPcFi6/C was observed and can be attributed to Co 2+ .
- the binding energy of Co2p3/2 was positively shifted 0.5 eV for the CoPcFi6 catalyst, which agrees with the DFT calculation results (FIGs.lC and ID ⁇ . More positive charges on the central Co of CoPcFi 6 tend to increase the Co 2+ peak energy in the XPS.
- Ag20 agrees well with what was reported.
- the contents of Ag20 on silver surface are calculated from the areas of two peaks at 368.8 and 368.1 eV, which are 10.36%, 11.56% and 12.78% for Ag/C, CoPc@Ag/C and CoPcFi 6 @Ag/C,
- the XPS results imply that electron transfer occurs between Ag and Co 2+ in CoPc@Ag/C and CoPcFi6@Ag/C catalysts, which are likely due to back electron donation from Ag to the Co metal atom.
- the electron transfer between the adsorbed organic molecules and the Ag substrate can be tuned by changing the ligand groups of the adsorbed molecules.
- FIG. 3 shows the ORR polarization curves obtained on CoPc/C, CoPcFi6/C, Ag/C, CoPc@Ag/C, CoPcFie@Ag/C and Pt/C (50 wt.%, ⁇ with a rotation rate at 2500 rpm in 0.1 M NaOH solutions saturated with oxygen.
- the half-wave potential, E1/2 (the potential corresponding to 50% of the peak current] for CoPc@Ag/C or CoPcFi6@Ag/C is 50 mV - 80 mV more positive compared to the E1/2 observed for the Ag/C.
- Ag-nanoparticles modified with CoPc or CoPcFi 6 macromolecules thus more actively interact with O2 than do the Ag/C catalysts.
- CoPcFi6@Ag/C catalysts is 50-80 mV more favorable than that on CoPc/C
- CoPc@Ag/C, CoPcFi6@Ag/C, CoPc/C and CoPcFi6/C catalysts are calculated as 3.85, 3.93, 3.97, 2.07 and 2.05 respectively.
- the ORR on either the CoPc/C or the CoPcFi6/C catalysts are mainly through a 2-electron pathway, both the CoPc@Ag/C and the CoPcFi6@Ag/C catalysts show a close 4 electron transfer, which is comparable to that on the Ag/C catalysts that carry the ORR via a 4- electron pathway in alkaline solutions.
- the formation of H2O2 during the ORR process can be monitored and the ORR pathways on the electrodes prepared with various catalysts can be verified.
- the inset of FIG. 3 gives the H2O2 yields on six catalyst specimens. On both Ag/C and Pt/C electrodes, no significant solution phase H2O2 was detected and thus the H2O2 yield was negligible, which supports a direct 4-electron pathway to produce water.
- the CoPc/C and the CoPcFi6/C electrodes a significant ring current was detected starting at the ORR onset potential of the disk electrode and up to 50% and 30% of the H2O2 yield was measured on the CoPc and the CoPcFi 6 electrode, respectively.
- H2O2 is a main product for the ORR catalyzed by the CoPc/C or the CoPcFi6/C catalysts.
- the disk limiting currents are as high as that on the Ag/ C catalyst, but the ring currents are slightly higher than that on the Ag/ C catalyst and much lower than those on the CoPc/C and the CoPcFi6/C catalysts.
- FIG. 4 illustrates mass-corrected Tafel plots of log Ik (mA cm 2 ) vs. the electrode potential E (vs. Hg/HgO] for the ORR on the electrodes prepared with various catalysts in an 02-saturated 0.1 M NaOH solution.
- E vs. Hg/HgO
- FIG. 4 illustrates mass-corrected Tafel plots of log Ik (mA cm 2 ) vs. the electrode potential E (vs. Hg/HgO] for the ORR on the electrodes prepared with various catalysts in an 02-saturated 0.1 M NaOH solution.
- These Tafel curves were obtained from the polarization curves of Fig.3 with a rotation rate of 2500 rpm.
- the Tafel plot slopes listed in Table 1 ⁇ at the lower overpotential region (where E > 0 V vs.
- Hg/HgO] for Pt/C and Ag/C catalysts are 58 and 59 mV dec 1 respectively, which close to 60 mV dec 1 and indicate that the first electron transfer is the rate- determining step at the low overpotentials.
- Electrode E1/2/V Iiim/mA Tafel plot slopes (mV dec 1 ⁇ f@ 0.5V, 2500) Low n High n
- the Tafel slope for Ag/C is 133 mV dec 1 , which is much higher than that of Pt/C (116 mV dec 1 ⁇ and accounts for the lower activity of Ag/C catalysts.
- the Tafel slopes for the CoPc@Ag/C and the CoPcFi6@Ag/C catalysts at the higher overpotential region drop significantly to 101 and 95 mV dec 1 respectively.
- the ORR kinetic current on the CoPc@Ag/C and the CoPcFi6@Ag/C is 1.46 mA cm -2 and 2.73 mA cm -2 , which is about 3.2 times higher than that of the Ag/C electrode(0.85 mA cm -2 ⁇ .
- the CoPc@Ag/C and the CoPcFi6@Ag/C catalysts display better performance than the Ag/C and the CoPc/C or the CoPcFi6/C catalysts, and are much close to that of Pt/C catalysts.
- the performance of the oxygen cathode prepared with various catalysts was tested in a cell in an oxygen saturated 6.0 M NaOH solution as the electrolyte. The i-E curves were recorded point-by-point with increasing current. The performance of the oxygen cathode was highly dependent on the catalyst used. FIG.
- FIG. 5 shows the polarization curves for oxygen reduction on the Ag/C, CoPc/C, CoPcFi6/C, CoPc@Ag/C,CoPcFi6@Ag/C and Pt/C cathodes.
- the polarization of the CoPc@Ag/ C and the CoPcFi6@Ag/ C cathode is significant lower than Ag/ C, CoPc/C and CoPcFi6/C electrodes in both low current density and high current density regions.
- the polarization of the CoPcFi6@Ag/ C electrode is almost the same as what was observed on the Pt/ C electrode, which improved significantly by comparing with the Ag/C, CoPc/C or CoPcFi6/C electrodes.
- the performance of oxygen electrodes with Ag/C, CoPc/C, CoPcFi6/C, CoPc@Ag/C, CoPcFi6@Ag/C and Pt/C catalysts are consistent with those obtained by the RRDE measurements.
- the electrocatalytic activity toward oxygen reduction was demonstrated to be tunable by adsorbing various CoPc or CoPcFi6 molecules on Ag nano-particle surfaces.
- 200 mg 60 wt.% silver loadings 110 on carbon black were prepared by a citrate-protecting method as following. 1066.2 mg sodium citric and 666.0 mg NaOH were mixed to prepared 111.0 mL 50 mM sodium citrate solution, and then 111.0 mL 10 mM AgN0 3 was added. 150 mL 7.4 mM NaBH 4 solution was added dropwise under vigorous stirring to obtain a yellowish-brown Ag colloid. 80 mg carbon black was taken to disperse into the above Ag colloid. After the suspension was stirred for 12 hours, the black suspension was filtered, washed and dried, and a 60 wt. Ag/C catalyst sample was obtained.
- CoPc or CoPcFi6- modified Ag/C 110, and carbon supported CoPc or CoPcFi6 105 catalyst were prepared by mixing 15 weight percent cobalt phthalocyanine or 15 weight percent cobalt hexadecafluoro phthalocyanine with 85 weight percent (60% weight percent Ag/C] or 85 weight percent carbon black uniformly in ethanol by ultrasonic stirring. After drying, the obtained samples were denoted as
- X-ray photoelectron spectroscopy was recorded by an imaging spectrometer using an Al Ka radiation (1486.6 eV ⁇ . The binding energies were calibrated relative to C (Is] peak from carbon composition of samples at 284.8 eV.
- Electrochemical activities of catalysts were measured by a setup consisting of a computer-controlled potentiostat, a radiometer speed control unit, and a rotating ring disk electrode radiometer (RRDE, glassy carbon with a diameter of 5.5 mm as the disk and with platinum as the ring ⁇ .
- Catalyst ink was prepared by ultrasonically mixing 2.0 mg of catalyst samples with 10 uL of the Nafion solution (5%], lmL of ethanol and lmL of de-ionized water. Then, 40 uL of the prepared catalyst ink was dropped on the surface of the glassy carbon to form a working electrode.
- the electrochemical measurements were conducted in an argon or oxygen-purged 0.1 M NaOH solution using a standard three- electrode cell with a Pt wire serving as the counter electrode and a Hg/HgO/0.1M OH- electrode used as the reference electrode respectively.
- H2O2 production in O2- saturated 0.1 M NaOH electrolytes was monitored in a RRDE configuration using a polycrystalline Pt ring biased at 0.3 V vs. Hg/HgO/0.1M
- the ring current firin ] was recorded simultaneously with the disk current (Idisk ⁇ . Collection efficiency (N] of the ring electrode was calibrated by K3Fe(CN ⁇ 6 redox reaction in an Ar-saturated 0.1 M NaOH solution.
- CoPcFi6@Ag/C and Pt/C catalysts were further characterized on oxygen electrode in a cell containing 6M NaOH solutions saturated with oxygen.
- a catalyst ink was prepared by ultrasonically-mixing 3 mg of the catalyst, 200 uL of ethanol and 44.5 uL of Nafion solution (5 wt.% ⁇ . The ink was pipetted on a 1.61 cm 2 gas diffusion layer to prepare oxygen electrode. The oxygen electrode was assembled into a cell with 0.71 cm 2 active surface area in the working electrode.
- a carbon sheet was used as the counter-electrode, and a Hg/HgO/6.0 M OH- electrode was used as the reference electrode.
- a 6.0 M NaOH solution was adopted as electrolyte to decrease the influence of IR drop in instead of 0.1M NaOH solution. Polarization curves were recorded galvanostatically with a stepwise increasing current at room temperature.
Abstract
A composition for catalyzing oxygen reduction reactions in alkaline media, including transition-metal macrocycles and metallic nano-particles. The metallic nanoparticles have diameters ranging from about 1 nm to about 500 nm and are typically selected from the group including Ag, Ni, Co, Au, W, Mo, Mn and combinations thereof.
Description
MACROCYCLE MODIFIED AG NANOPARTICULATE CATALYSTS WITH VARIABLE OXYGEN REDUCTION ACTIVITY IN ALKALINE MEDIA
CROSS-REFERENCE TO RELATED APPLICATIONS
This patent application claims priority to co-pending U.S. provisional patent application serial number 61/369,891, filed on August 2, 2010, and to copending U.S. provisional patent application serial number 61/418,060, filed on November 30, 2010.
ACKNOWLEDGEMENT
Research leading to this novel technology was federally supported by grant no. W911NF-07-2-0036 from the United States Army Research Laboratory. The government retains certain rights in this novel technology.
TECHNICAL FIELD
The novel technology relates generally to the field of electrochemistry, and, more particularly, to cobalt phthalocyanine and/or N4 macrocycle promoted Ag- based nano-metallic oxidation reduction reaction (ORR] catalysts.
BACKGROUND
Fuel cells, among other devices, typically employ a catalyst system for the oxygen electrode or air electrode to catalyze the ORR of the electrochemical device in alkaline media. Electrochemical devices include metal-air or sugar-air cells or batteries, and fuel cells such as H2/O2 fuel cells or direct alcohol fuel cells. Compared with the Pt-based catalysts for the ORR in the state-of-the-art proton exchange membrane fuel cells, non-Pt catalysts, including Ag, Au, Pd, Ni, manganese oxide, prophyrins, and phthalocyanines, are active and affordable for the ORR in alkaline media. Among these catalysts, the relatively inexpensive and abundant Ag is a top candidate to replace Pt for the ORR in alkaline media due to its relative high activity for the ORR through an approximated 4-electron pathway.
However, the ORR operation potential on Ag-based catalysts is still more than 100 mV lower than that on Pt-based catalysts, and the stability of Ag or Ag-based catalysts for the ORR is also a big concern. To develop non-Pt electrocatalysts with ORR activity and stability to be comparable with that of Pt-based catalysts is highly desirable for commercializing solid alkaline fuel cells, alkaline fuel cells or metal-air batteries. Thus, there remains a need to catalyst system that utilize more abundant and less expensive materials to yield an ORR operation potential comparable to that of Pt-based catalysts. The present invention addresses this need.
SUMMARY
The present novel technology relates to hybrid electrocatalytic systems including metallic nanoparticles incorporating transition-metal macrocycles exterior coatings or sheathes for catalyzing oxygen reduction reaction (ORR] in alkaline media, such as Ag nanopartiocles modified with a Co-based phthalocyanine surface treatment, for oxygen reduction reaction (ORR] in alkaline media.
One object of the present novel technology is to provide an improved catalyst for oxygen reduction reactions. Related objects and advantages of the present novel technology will be apparent from the following description.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A graphically illustrates the molecular structure of CoPc. FIG. IB graphically illustrates the molecular structure of CoPcFi6. FIG. 1C graphically illustrates the Mulliken charge of FIG. 1A. FIG. ID graphically illustrates the Mulliken charge of FIG. IB.
FIG. 2A shows the XPS narrow scan spectra of Co2p3/2 core level for Ag/C, CoPc@Ag/C, CoPcFi6@Ag/C, CoPc/C and CoPcFi6/C catalysts.
FIG. 2B shows the XPS narrow scan spectra of Ag3ds/2 for Ag/C,
CoPc@Ag/C, and CoPcFi6@Ag/C catalysts.
FIG. 3 shows the ORR polarization curves obtained on CoPc/C, CoPcFi6/C,
Ag/C, CoPc@Ag/C, CoPcFie@Ag/C and Pt/C (50 wt.%,} with a rotation rate at 2500 rpm in 0.1 M NaOH solutions saturated with oxygen.
FIG. 4 presents the mass-corrected Tafel plots of log Ik (mA cm 2) vs. the electrode potential E (vs. Hg/HgO] for the ORR on the electrodes prepared with various catalysts in an 02-saturated 0.1 M NaOH solution.
FIG. 5 graphically illustrates current density vs. potential for CoPc/C, CoPcFie/C, Ag/C, CoPc@Ag/C, CoPcFi6@Ag/C, and Pt/C, respectively.
FIG. 6A graphically illustrates a comparison of cyclic voltammetris of different catalysts in Ar-purged 0.1 M NaOH solution at 5th cycle, CoPc and CoPcFi6.
FIG. 6B graphically illustrates a comparison of cyclic voltammetris of different catalysts in Ar-purged 0.1 M NaOH solution at 5th cycle,Ag/C, CoPc@Ag/C
and CoPcFi6@Ag/C.
FIG. 6C graphically illustrates a comparison of cyclic voltammetris at first cycle at CoPc@Ag/C and CoPcFi6@Ag/C.
FIG. 7A-7F graphically illustrate the oxygen reduction polarization curves at 400,900, 1600 and 2500 rpm in 02-purged 0.1 M NaOH.
FIG.8 graphically illustrates Levich plots of (¾ reduction on Ag/C,
CoPc@Ag/C, CoPcF16@Ag/C, CoPc/C, CoPcF16/C and Pt/C catalysts.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
For the purposes of promoting an understanding of the principles of the novel technology and presenting its currently understood best mode of operation, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the novel technology is thereby intended, with such alterations and further modifications in the illustrated device and such further applications of the principles of the novel technology as illustrated therein being contemplated as would normally occur to one skilled in the art to which the novel technology relates.
The development of anion exchange membrane fuel cells (AEMFCs] has driven renewed interest in catalysts utilizing oxygen reduction reactions (ORRs] in alkaline media. Compared to proton exchange membrane fuel cells (PEMFCs], one of the advantages of the AEMFCs or alkaline fuel cells (AFCs] is the possibility of using other catalyst materials instead of the standard platinum or carbon-supported Pt electrocatalysts for the ORR. Several non-Pt catalysts, including Ag, Au, Pd, cobalt and manganese oxide, prophyrins, and
phthalocyanines, have been well studied. Among various catalyst systems, the relatively inexpensive and abundant Ag is an economically advantageous choice to replace Pt as the cathode catalyst for applying in AEMFCs. In addition to cost advantages, Ag has a relative high electrocatalytic activity for reducing O2 via an
approximated 4-electron ORR pathway. However, the ORR kinetics on Ag nano- particles in alkaline media are problematic, as ORR overpotentials on Ag catalysts are more than 100 mV higher than that on Pt catalysts under the same conditions.
Adsorbed coordination compounds on metallic substrates show promise with respect to the controlled functionalization of surfaces on the nanoscale. Planar metal complexes such as M(II]-porphyrins (MP] and M(II}- phthalocyanines (MPc] are particularly interesting due to their physical and chemical properties. The metal centers of MP or MPc molecules typically possess no axial ligands and represent coordinatively unsaturated sites with potential catalytic functionality. For example, CoPc and FePc molecules are well known to have desirable electrocatalytic activities for reducing O2 molecules. Electronic and geometric properties of Co-tetraphenyl-porphyrin (CoTPP] layers on Ag(lll] have been investigated using photoelectron diffraction (PED], near-edge x-ray absorption fine-structure (NEXAFS] measurements and discrete Fourier transform (DFT] calculations, revealing that the central Co atom of the Co-TPP resides predominantly above fee and hep hollow sites of the Ag (111] substrate and that the interaction of the CoTPP with the Ag(lll] substrate can induce modifications of the CoTPP molecular configuration, such as a distorted macrocycle with a shifted position of the Co metal center. Similarly, the interaction of a number of phthalocyanine molecules (SnPc, PbPc, and CoPc] with the Ag(lll] surface has been investigated. Each of the phthalocyanine molecules (SnPc, PbPc and CoPc] has been found to donate charge to the silver surface, and
that back donation from Ag to the metal atom Co, Sn, or Pb is only significant for CoPc. The adsorbed MP or MPcs molecules were found to induce a local restructuring process of the metallic Ag substrate, which could alter Ag's functionality and the morphology of the adsorbed MP or MPc molecules.
The present novel technology relates to hybrid catalysts, specifically hybrid electrocatalytic systems 100 incorporating metal chelate compounds or transition-metal macrocycles 105 with metallic or metal oxide nano-particles 110 for catalyzing oxygen reduction reaction (ORR] in alkaline media. The ORR catalytic activity and stability of the hybrid catalysts 100 combining transition- metal macrocycles 105 with metallic nano-particles llOare significantly improved over the ORR catalytic activity and stability of either the transition- metal macrocycles 105 or the nano-sized metallic catalysts 110, and is comparable to the ORR catalytic activity and stability of traditional, and significantly more expensive, catalytic systems such as carbon supported Pt (Pt/C}. For example, integration of Co-macrocycles 105 with Ag or Ag-based nanoparticles 110 (typically about 1 nm to about 1000 nm) yields a high performance and stable hybrid catalytic system for the ORR in alkaline media. The Co-macrocycles 105 may include Co-phthalocyanines (CoPc],
cobalt(II]l,2,3,4,8,9,10,ll,15,16,17,18,22,23,24,25-hexadecafluoro-29H,31H- phthalocyanine (CoPc Fi6], Co-tetramethoxyphenylporphirine (CoTMPP], and other Co-organic molecules containing Co-N2 or Co-N4 structures and the like.
The transition-metal macrocycles 105 are typically large organic molecules containing transition-metals (Co, Fe, Mn, Ni, and the like], which are typically bonded with two or four nitrogen atoms. The large organic molecules are typically selected to be phthalocyanine, porphyrin, derives thereof, or the like. Metallic nanoparticles include Ag/Ag-based, Co/Co-based and other metal/metal-based particles. Metals in metallic nanoparticles 110 may be in various forms, such as metallic, alloyed with other metals, metal oxide, and etc. The metallic nanoparticles may include Ag, Pt, Pd, Ni, Co, Au, W, Mo, Mn, Fe, Ir, Sn, Cu, Zn, Os, Rh, Ru, Ti, V, Cr, Zr, Mo, their oxides, and combinations thereof. The particle size of metallic nanoparticles 110 is typically in the range of about 0.1 nm to about 5000 nm, more typically from about 1 nm to about 1000 nm.
Metallic nanoparticles 110 may be supported on carbon, unsupported, or mixed with carbon or other electrically conducting or semiconducting material. Typical support structures include carbon black, carbon nanotubes, carbon nanofibers, fullerenes, and other carbon materials with different morphologies, or
electrically conducting polypyrrole and its derivates, nickel powder, and the like.
Macrocycles 105 can be physically mixed with carbon-supported or non- carbon supported metallic nanoparticles 110, or adsorbed physically or chemically on carbon-supported or non-carbon supported metallic nanoparticle 110 surfaces to form a hybrid catalyst system 100. By incorporating transition-metal macrocycles 105 onto metallic nano-particles 110, physical and electrochemical properties of the surface of nano-metallic catalysts 100 can be modified significantly. For example,
coating Co-phthalocyanines (CoPc] 105 on carbon supported Ag or AgCo nano- particles 110 modifies both the electronic properties and geometrical structures of both metallic surfaces and CoPc surface, yielding improved oxygen and/or water adsorption and reducing OH- adsorption. Therefore, improved ORR activity and stability on the invented hybrid CoPc + Ag/Ag-based catalysts 100 are achieved.
By combining electrochemical measurements with theoretical DFT calculations, key factors that control ORR activity and stability on CoPc and FePc model electrodes may be better understood. Adsorption energy of O2, OH- and HOOH on CoPc or FePc molecules plays a key role to determine the ORR activity and stability. DFT simulation and electrochemical measurement results suggest that the ORR on fully halogenated CoPcFi6 has more favorable O2 reduction potentials than on CoPc due to the fluorine substitution, impacting the molecular electron affinity. The electronic and geometric properties of the metal centers (Co or Fe] of the adsorbed molecules 105 can be co-determined by the underlying substrate atoms 110.
ORR activities on carbon supported Ag nano-particles 110 modified with CoPc or CoPcFie molecules 105 (CoPc@Ag/C and CoPcFi6@Ag/Q. CoPc@Ag/C or CoPcFi6@Ag/C catalysts lOOhave more favorable O2 reduction potentials and rate constants than CoPc/C (and the CoPcFi6/C] catalysts or Ag/C catalysts. The ORR activity of the Ag nano-catalysts 100 is variable or tunable by adjusting the compositions of the adsorbed organic molecules. A new class of "hybrid"
catalysts 100 based on the adsorption of organic molecules 110 on metallic nano- particles 105 for meeting performance and durability requirements in fuel cell applications is thus developed.
Example 1
Sixty weight percent Ag loadings 110 on carbon black were prepared by a citrate-protecting method. CoPc or CoPcFi6-modified Ag/C catalyst 110 were prepared by mixing 15 weight percent CoPc or 15 weight percent CoPcFi6 with 85 weight percent (60 weight percent Ag/C] uniformly in ethanol by ultrasonic stirring, which were denoted as CoPc@Ag/C and CoPcFi6@Ag/C respectively. The CoPc@Ag/C and CoPcFi6@Ag/C samples could also be prepared by adsorbing CoPc directly onto the Ag/C electrodes from a DMF solution containing 10-5 M CoPc. The geometrical and electronic structures of CoPc and CoPcFi6 molecules were calculated using DFT Composition and electrochemical properties of the catalysts 100 were characterized by x-ray photoelectron spectroscopy (XPS], cyclic voltammetry (CV], rotating ring disk electrode (RRDE] and oxygen electrode tests.
Example 2
A cathode for catalyzing ORRs in alkaline media may be produced comprising metal chelate compounds 105 and metallic and/or oxide
nanoparticles 110. Likewise, the same materials may be used to produce an anode for catalyzing hydrogen, hydrazine, alcohol, and/or glucose oxidation
reactions in alkaline media. The metallic nanoparticles 110 may be sleected from the group including Ag, Pt, Pd, Ni, Co, Au, W, Mo, Mn, Fe, Ir, Sn, Cu, Zn, Os, Rh, Ru, Ti, V, Cr, Zr, Mo, their oxides, and combinations thereof. The metal chelate 105 may be selected from the group including Co, Fe, Ni, Mn, Zn, Cr, Cu, and/or Sn phthalocyanines, porphyrins, and their derivatives, with or without heat treatment and in concentrations of from about 1 ppm to about 80 weight percent of the catalyst material. The transition-metal macrocycles 105 and nanoparticles 110 may or may not be dispersed in carbon and/or metal oxide supports for electronic conductivit catalyst distribution, and stability purposes. Likewise, anodes and cathodes prepared as described above may be used in the production of anion exchange membrane fuel cells or metal-air batteries.
FIG. 1 shows the DFT optimized CoPc and CoPcFi6 molecular structures, which are planar 4-fold symmetrical aromatic macrocyclic organic molecule. When the peripherical hydrogen atoms of the benzene rings of the CoPc (FIG.1A] are substituted with fluorine atoms of the CoPcFi6 (FIG.1B], the Co-N bond distance is increased, and the charges on the central Co become increasingly positive. Using DFT, the adsorption energy of O2 on the CoPcFi6 is calculated as 0.467 eV, which is 0.065 eV higher than that on the CoPc molecule. Higher O2 adsorption energy results more positive ORR onset and half-wave potentials. Fluorine atoms induce a higher electron affinity to the entire CoPc molecule, consequently leading to a much more reactive system.
FIG. 2A illustrates the XPS narrow scan spectra of Co2p3/2 core level for
Ag/C, CoPc@Ag/C, CoPcFi6@Ag/C, CoPc/C and CoPcFi6/C catalysts. A peak at 780.9 eV for CoPc/C and at 781.4 eV for CoPcFi6/C was observed and can be attributed to Co2+. The binding energy of Co2p3/2 was positively shifted 0.5 eV for the CoPcFi6 catalyst, which agrees with the DFT calculation results (FIGs.lC and ID}. More positive charges on the central Co of CoPcFi6 tend to increase the Co2+ peak energy in the XPS. For the CoPc@Ag/C and CoPcFi6@Ag/C, the peak positions of Co2p3/2 of Co2+ do not shift compared those observed for the CoPc/C and the CoPcFi6/C catalysts. However, another new peak at 779.3 eV appears clearly for the CoPc@Ag/C and the CoPcFi6@Ag/C catalysts, which is attributed to Co2p3/2 of Co0 and indicates that the electronic properties of the metal centers (Co] of the adsorbed CoPc or CoPcFi6 molecules are affected by the underlying Ag substrate atoms. From the XPS narrow scan spectral of Ag3ds/2 in FIG. 2B, two peaks located at 368.8 and 368.1 eV are distinguished by de-convolution, which are attributed to Ag3ds/2 of Ag° and Ag+ respectively. The observed binding energy shift of the 3d peak toward the negative direction for Ag metal versus
Ag20 agrees well with what was reported. The contents of Ag20 on silver surface are calculated from the areas of two peaks at 368.8 and 368.1 eV, which are 10.36%, 11.56% and 12.78% for Ag/C, CoPc@Ag/C and CoPcFi6@Ag/C,
respectively. The XPS results imply that electron transfer occurs between Ag and Co2+ in CoPc@Ag/C and CoPcFi6@Ag/C catalysts, which are likely due to back electron donation from Ag to the Co metal atom. The electron transfer between the adsorbed organic molecules and the Ag substrate can be tuned by changing
the ligand groups of the adsorbed molecules.
FIG. 3 shows the ORR polarization curves obtained on CoPc/C, CoPcFi6/C, Ag/C, CoPc@Ag/C, CoPcFie@Ag/C and Pt/C (50 wt.%,} with a rotation rate at 2500 rpm in 0.1 M NaOH solutions saturated with oxygen. The half-wave potential, E1/2 (the potential corresponding to 50% of the peak current] for CoPc@Ag/C or CoPcFi6@Ag/C is 50 mV - 80 mV more positive compared to the E1/2 observed for the Ag/C. Ag-nanoparticles modified with CoPc or CoPcFi6 macromolecules thus more actively interact with O2 than do the Ag/C catalysts. The effect for shifting the E1/2 to the positive direction by the adsorbed CoPcFi6 molecules on the Ag/C catalysts is more significant than the CoPc molecules. By further precisely varying the geometry and electronic structures of the adsorbed Co-macrocyclic molecules on the Ag-nano particle surfaces, additional improvement to the E1/2 is anticipated.
While the half-wave potential for the ORR on the CoPc@Ag/C or
CoPcFi6@Ag/C catalysts is 50-80 mV more favorable than that on CoPc/C,
CoPcFi6/C or Ag/ C catalysts, the observed limiting currents on the CoPc@Ag/ C or CoPcFi6@Ag/C catalysts are as high as what is observed on the Ag/C catalyst, and almost twice higher than that of CoPc/C and CoPcFi6/C catalysts (FIG. 3}. The electrochemical reduction of O2 is a multi-electron reaction that has two main pathways. The first involves the transfer of 2-electrons to produce H2O2, while the second involves a direct 4-electron pathway to produce water. The limiting currents at different rotation rates can be used to construct the Levich
plots (FIG. 8}. The number of electron transferred for the ORR on Ag/ C,
CoPc@Ag/C, CoPcFi6@Ag/C, CoPc/C and CoPcFi6/C catalysts are calculated as 3.85, 3.93, 3.97, 2.07 and 2.05 respectively. Although the ORR on either the CoPc/C or the CoPcFi6/C catalysts are mainly through a 2-electron pathway, both the CoPc@Ag/C and the CoPcFi6@Ag/C catalysts show a close 4 electron transfer, which is comparable to that on the Ag/C catalysts that carry the ORR via a 4- electron pathway in alkaline solutions.
By using the rotating ring disk electrode (RRDE] measurements, the formation of H2O2 during the ORR process can be monitored and the ORR pathways on the electrodes prepared with various catalysts can be verified. The inset of FIG. 3 gives the H2O2 yields on six catalyst specimens. On both Ag/C and Pt/C electrodes, no significant solution phase H2O2 was detected and thus the H2O2 yield was negligible, which supports a direct 4-electron pathway to produce water. For the CoPc/C and the CoPcFi6/C electrodes, a significant ring current was detected starting at the ORR onset potential of the disk electrode and up to 50% and 30% of the H2O2 yield was measured on the CoPc and the CoPcFi6 electrode, respectively. This indicates that H2O2 is a main product for the ORR catalyzed by the CoPc/C or the CoPcFi6/C catalysts. For the CoPc@Ag/C and the CoPcFi6@Ag/C catalysts, the disk limiting currents are as high as that on the Ag/ C catalyst, but the ring currents are slightly higher than that on the Ag/ C catalyst and much lower than those on the CoPc/C and the CoPcFi6/C catalysts. The observed ring currents on either the CoPc@Ag/C or the CoPcFi6@Ag/C
catalysts are likely due to the non-optimized preparation method, such that CoPc or CoPcFi6 molecules are not fully adsorbed on the silver surfaces and the ORR could carry out on the CoPc/C or the CoPcFi6/C catalysts to produce H2O2 as the final product. However, less than 10% of the H2O2 yields are observed to be at potentials lower than -0.5V vs. Hg/HgO for either the CoPc@Ag/ C or the
CoPcFi6@Ag/C catalysts, which indicates that the ORRs occur mainly on the CoPc or CoPcFi6 modified Ag nano-particle surfaces. These RRDE results also confirm the results calculated from the Levich equation that the ORR electron exchange number is close to 4 electrons for the ORR on the Ag/C, the CoPc@Ag/C or the CoPcFi6@Ag/C catalysts, but about 2 electrons for the ORR on the CoPc/C or the CoPcFie/C.
FIG. 4 illustrates mass-corrected Tafel plots of log Ik (mA cm 2) vs. the electrode potential E (vs. Hg/HgO] for the ORR on the electrodes prepared with various catalysts in an 02-saturated 0.1 M NaOH solution. These Tafel curves were obtained from the polarization curves of Fig.3 with a rotation rate of 2500 rpm. The Tafel plot slopes (listed in Table 1} at the lower overpotential region (where E > 0 V vs. Hg/HgO] for Pt/C and Ag/C catalysts are 58 and 59 mV dec 1 respectively, which close to 60 mV dec 1 and indicate that the first electron transfer is the rate- determining step at the low overpotentials.
Table 1: Electrochemical parameters for the oxygen reduction estimated from
polarization curves
Electrode E1/2/V Iiim/mA Tafel plot slopes (mV dec 1}
f@ 0.5V, 2500) Low n High n
CoPc/C -0.168 0.87 N/A 78
CoPcFie/C -0.152 0.93 N/A 70
Ag/C -0.214 1.56 59 133
CoPc@Ag/C -0.164 1.58 55 101
CoPcFi6@Ag/C -0.132 1.61 55 95
Pt/C -0.109 1.63 58 116
At the higher overpotential region (where E < -100 mV vs. Hg/HgO], the Tafel slope for Ag/C is 133 mV dec 1, which is much higher than that of Pt/C (116 mV dec 1} and accounts for the lower activity of Ag/C catalysts. After modification of Ag/C catalysts with either the CoPc or the CoPcFi6 molecules, the Tafel slopes for the CoPc@Ag/C and the CoPcFi6@Ag/C catalysts at the higher overpotential region drop significantly to 101 and 95 mV dec 1 respectively. At an alkaline fuel cell cathode working potential(-0.100 V vs Hg/HgO, equivalent to an overpotential of 0.320V], the ORR kinetic current on the CoPc@Ag/C and the CoPcFi6@Ag/C is 1.46 mA cm-2 and 2.73 mA cm-2, which is about 3.2 times higher than that of the Ag/C electrode(0.85 mA cm-2}. In a pure oxygen and 0.1 M NaOH electrolyte environment, the CoPc@Ag/C and the CoPcFi6@Ag/C catalysts display better performance than the Ag/C and the CoPc/C or the CoPcFi6/C catalysts, and are much close to that of Pt/C catalysts. The performance of the oxygen cathode prepared with various catalysts was tested in a cell in an oxygen saturated 6.0 M NaOH solution as the electrolyte. The i-E curves were recorded point-by-point with increasing current. The performance of the oxygen cathode was highly dependent on the catalyst used. FIG. 5 shows the polarization curves for oxygen reduction on the Ag/C, CoPc/C,
CoPcFi6/C, CoPc@Ag/C,CoPcFi6@Ag/C and Pt/C cathodes. The polarization of the CoPc@Ag/ C and the CoPcFi6@Ag/ C cathode is significant lower than Ag/ C, CoPc/C and CoPcFi6/C electrodes in both low current density and high current density regions. At the high current density region, the polarization of the CoPcFi6@Ag/ C electrode is almost the same as what was observed on the Pt/ C electrode, which improved significantly by comparing with the Ag/C, CoPc/C or CoPcFi6/C electrodes. The performance of oxygen electrodes with Ag/C, CoPc/C, CoPcFi6/C, CoPc@Ag/C, CoPcFi6@Ag/C and Pt/C catalysts are consistent with those obtained by the RRDE measurements. The electrocatalytic activity toward oxygen reduction was demonstrated to be tunable by adsorbing various CoPc or CoPcFi6 molecules on Ag nano-particle surfaces.
Other hybrid catalyst systems, including Co-N4 or N2 macrocycles with other forms of nano-sized metals (such as Ag, Ni, Co, Au, W, Mo, Mn] and their based nanoparticles, would likewise be expected to exhibit improved ORR activity and stability
Catalysts preparation
200 mg 60 wt.% silver loadings 110 on carbon black were prepared by a citrate-protecting method as following. 1066.2 mg sodium citric and 666.0 mg NaOH were mixed to prepared 111.0 mL 50 mM sodium citrate solution, and then 111.0 mL 10 mM AgN03 was added. 150 mL 7.4 mM NaBH4 solution was added dropwise under vigorous stirring to obtain a yellowish-brown Ag colloid.
80 mg carbon black was taken to disperse into the above Ag colloid. After the suspension was stirred for 12 hours, the black suspension was filtered, washed and dried, and a 60 wt. Ag/C catalyst sample was obtained. CoPc or CoPcFi6- modified Ag/C 110, and carbon supported CoPc or CoPcFi6 105 catalyst were prepared by mixing 15 weight percent cobalt phthalocyanine or 15 weight percent cobalt hexadecafluoro phthalocyanine with 85 weight percent (60% weight percent Ag/C] or 85 weight percent carbon black uniformly in ethanol by ultrasonic stirring. After drying, the obtained samples were denoted as
CoPc@Ag/C, CoPcFie@Ag/C, CoPc/C and CoPcFi6/C respectively.
XPS characterization
X-ray photoelectron spectroscopy (XPS] was recorded by an imaging spectrometer using an Al Ka radiation (1486.6 eV}. The binding energies were calibrated relative to C (Is] peak from carbon composition of samples at 284.8 eV.
Electrochemical characterization
Electrochemical activities of catalysts were measured by a setup consisting of a computer-controlled potentiostat, a radiometer speed control unit, and a rotating ring disk electrode radiometer (RRDE, glassy carbon with a diameter of 5.5 mm as the disk and with platinum as the ring}. Catalyst ink was prepared by ultrasonically mixing 2.0 mg of catalyst samples with 10 uL of the Nafion solution (5%], lmL of ethanol and lmL of de-ionized water. Then, 40 uL
of the prepared catalyst ink was dropped on the surface of the glassy carbon to form a working electrode. The electrochemical measurements were conducted in an argon or oxygen-purged 0.1 M NaOH solution using a standard three- electrode cell with a Pt wire serving as the counter electrode and a Hg/HgO/0.1M OH- electrode used as the reference electrode respectively. H2O2 production in O2- saturated 0.1 M NaOH electrolytes was monitored in a RRDE configuration using a polycrystalline Pt ring biased at 0.3 V vs. Hg/HgO/0.1M
The ring current firin ] was recorded simultaneously with the disk current (Idisk}. Collection efficiency (N] of the ring electrode was calibrated by K3Fe(CN}6 redox reaction in an Ar-saturated 0.1 M NaOH solution. The value of the collection efficiency (N = Iring/ Idisk] determined is 0.41 for the Pt/C electrode. The fractional yields of H2O2 in the ORR were calculated from the RRDE experiments as XH202 = [2 Iring/N) / (Idisk
+ Iring/N}. Oxygen electrode characterization
Catalyst performance of Ag/C, CoPc/C, CoPcFi6/C, CoPc@Ag/C,
CoPcFi6@Ag/C and Pt/C catalysts were further characterized on oxygen electrode in a cell containing 6M NaOH solutions saturated with oxygen. A catalyst ink was prepared by ultrasonically-mixing 3 mg of the catalyst, 200 uL of ethanol and 44.5 uL of Nafion solution (5 wt.%}. The ink was pipetted on a 1.61 cm2 gas diffusion layer to prepare oxygen electrode. The oxygen electrode was assembled into a cell with 0.71 cm2 active surface area in the working electrode.
A carbon sheet was used as the counter-electrode, and a Hg/HgO/6.0 M OH- electrode was used as the reference electrode. A 6.0 M NaOH solution was adopted as electrolyte to decrease the influence of IR drop in instead of 0.1M NaOH solution. Polarization curves were recorded galvanostatically with a stepwise increasing current at room temperature.
While the novel technology has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character. It is understood that the
embodiments have been shown and described in the foregoing specification in satisfaction of the best mode and enablement requirements. It is understood that one of ordinary skill in the art could readily make a nigh-infinite number of insubstantial changes and modifications to the above-described embodiments and that it would be impractical to attempt to describe all such embodiment variations in the present specification. Accordingly, it is understood that all changes and modifications that come within the spirit of the novel technology are desired to be protected.
Claims
1. A composition for catalyzing oxygen reduction reactions in alkaline media, comprising:
a plurality of metallic nanoparticles; and
transition-metal macrocycles operationally connected to the metallic nanoparticles to define catalyst compound particles;
wherein the metallic nanoparticles are generally spherical;
wherein the metallic nanoparticles are substantially between about 1 nanometer and about 1000 nanometers in diameter.
2. The composition of claim 1 wherein the transition-metal macrocycles are selected from the group including Co, Fe, Ni, and Mn
phthalocyanines, Co, Fe, Ni, and Mn porphyrins, and derivatives thereof.
3. The composition of claim 1 wherein the metallic nanoparticles are selected from the group including Ag, Ni, Co, Au, W, Mo, Mn and combinations thereof .
4. The composition of claim 1 wherein the metallic nanoparticles have diameters ranging from about 1 nm to about 500 nm.
5. The composition of claim 1 and further comprising carbon support structures connected to respective catalyst compound particles.
6. The composition of claim 5 wherein the carbon support structures are selected from the group including carbon nanotubes, fullerenes, carbon nanofibers, and carbon black.
7. The composition of claim 1 wherein the transition-metal macrocycles are selected from the group including fully halogenated CoPcFi6, fully halogenated CoPcCNi6, and combinations thereof.
8. A method for catalyzing oxygen reduction reactions in an alkaline environment, comprising:
preparing a combination of Co-based phthalocyanines macrocycles and metallic nano-particles to define a plurality of catalyst composition particles; enveloping the catalyst composition in an alkaline environment; and catalyzing an oxygen reaction at the catalyst composition;
wherein the catalyst composition particles are sized between about 1 nanometer and about 500 nanometers.
9. A method for catalyzing oxygen reduction reactions in an alkaline environment, comprising:
defining a catalyst composition as a combination of metallic nanoparticles, wherein each respective particle has a surface treatment of operationally connected transition-metal macrocycles;
enveloping the catalyst composition in an alkaline environment; and catalyzing an oxygen reduction reaction at the catalyst composition.
10. The method of claim 9 wherein the transition-metal macrocycles are selected from the group including Co, Fe, Ni, and Mn phthalocyanines, Co, Fe, Ni, and Mn porphyrins, and derivatives thereof.
11. The method of claim 9 wherein the metallic nanoparticles are selected from the group including Ag, Ni, Co, Au, W, Mo, Mn and combinations thereof .
12. The method of claim 9 wherein the metallic nanoparticles have diameters ranging from about 1 nm to about 500 nm.
13. A composition for catalyzing oxidation reduction reactions in alkaline media, comprising:
a nanoparticle selected from the group including Ag, Ni, Co, Au, W, Mo, Mn, and combinations thereof; and
a transition-metal macrocycle disposed on the surface of the
nanoparticles.
14. The composition of claim 13 wherein the transition-metal macrocycle is selected from the group including Co phthalocyanines, Fe phthalocyanines, Ni phthalocyanines, Mn phthalocyanines, Co porphyrins, Fe porphyrins, Ni porphyrins, Mn porphyrins, and derivatives thereof.
15. The composition of claim 13 and further comprising carbon support structures connected to respective catalyst compound particles.
16. The composition of claim 15 wherein the carbon support structures are selected from the group including carbon nanotubes, fullerenes, carbon nanofibers, and carbon black.
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