CA2160718C - Electrocatalyst material comprising a platinum alloy on a conductive support - Google Patents
Electrocatalyst material comprising a platinum alloy on a conductive support Download PDFInfo
- Publication number
- CA2160718C CA2160718C CA002160718A CA2160718A CA2160718C CA 2160718 C CA2160718 C CA 2160718C CA 002160718 A CA002160718 A CA 002160718A CA 2160718 A CA2160718 A CA 2160718A CA 2160718 C CA2160718 C CA 2160718C
- Authority
- CA
- Canada
- Prior art keywords
- gold
- electrocatalyst
- electrocatalyst material
- platinum
- catalyst
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- 239000000463 material Substances 0.000 title claims abstract description 32
- 239000010411 electrocatalyst Substances 0.000 title claims abstract description 29
- 229910001260 Pt alloy Inorganic materials 0.000 title abstract description 5
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims abstract description 46
- 239000010931 gold Substances 0.000 claims abstract description 32
- 229910052737 gold Inorganic materials 0.000 claims abstract description 27
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 claims abstract description 22
- 229910052697 platinum Inorganic materials 0.000 claims abstract description 18
- 239000003792 electrolyte Substances 0.000 claims abstract description 15
- 239000002253 acid Substances 0.000 claims abstract description 14
- 239000003054 catalyst Substances 0.000 claims description 29
- 239000000446 fuel Substances 0.000 claims description 20
- 239000002002 slurry Substances 0.000 claims description 13
- 238000005275 alloying Methods 0.000 claims description 10
- 229910052759 nickel Inorganic materials 0.000 claims description 10
- 238000000034 method Methods 0.000 claims description 8
- 238000011068 loading method Methods 0.000 claims description 5
- 229910052804 chromium Inorganic materials 0.000 claims description 4
- 229910052748 manganese Inorganic materials 0.000 claims description 4
- 238000004519 manufacturing process Methods 0.000 claims description 4
- 150000001875 compounds Chemical class 0.000 claims description 3
- 229910052802 copper Inorganic materials 0.000 claims description 2
- 229910052735 hafnium Inorganic materials 0.000 claims description 2
- 229910052742 iron Inorganic materials 0.000 claims description 2
- 230000000737 periodic effect Effects 0.000 claims description 2
- 229910052703 rhodium Inorganic materials 0.000 claims description 2
- 239000010948 rhodium Substances 0.000 claims description 2
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 claims description 2
- 229910052719 titanium Inorganic materials 0.000 claims description 2
- 229910052726 zirconium Inorganic materials 0.000 claims description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 14
- 229910052799 carbon Inorganic materials 0.000 description 12
- 230000000694 effects Effects 0.000 description 11
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 6
- 239000001301 oxygen Substances 0.000 description 6
- 229910052760 oxygen Inorganic materials 0.000 description 6
- 230000002572 peristaltic effect Effects 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 5
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 4
- 239000004810 polytetrafluoroethylene Substances 0.000 description 4
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 3
- 239000000706 filtrate Substances 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- 239000004215 Carbon black (E152) Substances 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 2
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 description 2
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical compound [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 239000008098 formaldehyde solution Substances 0.000 description 2
- 229930195733 hydrocarbon Natural products 0.000 description 2
- 150000002430 hydrocarbons Chemical class 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 230000002209 hydrophobic effect Effects 0.000 description 2
- 239000012528 membrane Substances 0.000 description 2
- 239000004570 mortar (masonry) Substances 0.000 description 2
- 239000007800 oxidant agent Substances 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 239000000376 reactant Substances 0.000 description 2
- 229910000030 sodium bicarbonate Inorganic materials 0.000 description 2
- 229910004042 HAuCl4 Inorganic materials 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 239000006230 acetylene black Substances 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- HSFWRNGVRCDJHI-UHFFFAOYSA-N alpha-acetylene Natural products C#C HSFWRNGVRCDJHI-UHFFFAOYSA-N 0.000 description 1
- 239000006229 carbon black Substances 0.000 description 1
- 235000019241 carbon black Nutrition 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 239000002322 conducting polymer Substances 0.000 description 1
- 229920001940 conductive polymer Polymers 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 125000002534 ethynyl group Chemical group [H]C#C* 0.000 description 1
- UQSQSQZYBQSBJZ-UHFFFAOYSA-N fluorosulfonic acid Chemical compound OS(F)(=O)=O UQSQSQZYBQSBJZ-UHFFFAOYSA-N 0.000 description 1
- 238000009472 formulation Methods 0.000 description 1
- 239000006232 furnace black Substances 0.000 description 1
- 229910052733 gallium Inorganic materials 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 229920001600 hydrophobic polymer Polymers 0.000 description 1
- 230000008676 import Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- -1 polytetrafluoroethylene Polymers 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 235000017557 sodium bicarbonate Nutrition 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229910052723 transition metal Inorganic materials 0.000 description 1
- 150000003624 transition metals Chemical class 0.000 description 1
Classifications
-
- 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
- H01M4/92—Metals of platinum group
- H01M4/925—Metals of platinum group supported on carriers, e.g. powder carriers
- H01M4/926—Metals of platinum group 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
- 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
- B01J23/52—Gold
-
- 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
- H01M4/92—Metals of platinum group
-
- 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
- H01M4/92—Metals of platinum group
- H01M4/921—Alloys or mixtures with metallic elements
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2300/00—Electrolytes
- H01M2300/0002—Aqueous electrolytes
- H01M2300/0005—Acid electrolytes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2300/00—Electrolytes
- H01M2300/0017—Non-aqueous electrolytes
- H01M2300/0065—Solid electrolytes
- H01M2300/0082—Organic polymers
-
- 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
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Catalysts (AREA)
- Conductive Materials (AREA)
- Contacts (AREA)
- Inert Electrodes (AREA)
- Electroplating And Plating Baths Therefor (AREA)
- Transition And Organic Metals Composition Catalysts For Addition Polymerization (AREA)
Abstract
An electrocatalyst material for use in an acid electrolyte environment, comprising platinum or a platinum alloy supported on a conductive support, and gold, gives unexpectedly improved performance over similar electrocatalysts without gold.
Description
ELECTROCATALYST MATERIAL COMPRISING A PLATINUM ALLOY ON
A CONDUCTIVE SUPPORT
This invention concerns an improved catalyst material, and in particular an improved electrocatalyst material for use in acid electrolyte fuel cell.
In the art of fuel cells, there have been very many proposals for the production of electrocatalysts which are used to coat one or both of the electrodes. It is useful to recall that in a fuel cell, a fuel, which may be hydrogen, a hydrocarbon or an oxygen-containing fuel such as methanol, is oxidised at a fuel electrode (anode) and oxygen is reduced at the cathode. An electrolyte contacts the electrodes, and may be alkaline or acidic, liquid or solid. The phosphoric acid fuel cell (PAFC) is the type of fuel cell closest to commercialisation and there are a number of demonstration units, especially in Japan where there are considerable economic and environmental pressures to reduce imports of hydrocarbon fuels and to cut polluting emissions from power generation. Many people consider that fuel cells are, however, unlikely to get beyond the demonstration stage, because the power output is too low for the capital costs involved. In the PAFC, power output is limited in part by the activity of the cathode catalyst. Increasing cathode catalyst activity can result in higher power density at the same efficiency. 'the capital cost per unit of power is therefore reduced in proportion to the increase in performance. Because the cost of the cathode catalyst is only a fraction of the cost of the fuel cell stack, increasing the power density of the stack reduces the capital cost per unit power out of all proportion to the value of the catalyst per se. It is therefore widely recognised that a cathode catalyst with improved performance would have great value in reducing overall capital cost per unit power.
We have found, surprisingly, that the addition of gold to an existing electrocatalyst, used in an acid electrolyte fuel cell, gives an improved performance catalyst. Previously, gold has been considered ineffective as an electrocatalysf under acid conditions, mainly because of the weakness of the metal-oxygen bond strength.
(See, for example, "Fuel Cell Handbook", Eds A J Appleby and F R Foulkes, p 383, Van Norstrand Reinhold, NY (1989) and US Patent No 3,223,556.) The present invention provides an electrocatalyst material for use in an acid electrolyte environment, comprising platinum alloyed with at least one alloying element and gold, supported on a conductive support, the atomic ratio of platinum to the alloying element being in the range 80:20 to 20:80, and wherein the gold is present in a loading of 0.0001 up to but not including 3wt% of the total catalyst weight.
WO 94/24710 _ ~ ~ PCT/GB94/00835 3 .,'~, ,..
This invention also provides an electrode for use in an acid electrolyte environment containing the electrocatalyst of the present invention.
Yet fiuther, this invention provides an acid electrolyte fuel cell employing the electrocatalyst material of the present invention.
Where the electrocaialyst material comprises a platinum alloy, preferably the alloying elements) are selected from the transition metals, more preferably from Groups IVB, VIB, VIIB, VIII, IB and IIIA of the Periodic Table in "Handbook of Chemistry and Physics"; 64th Edition, CRC Press. Even more preferably, the alloying elements are selected from one or more of Ti, Cr, Mn, Fe, Co, Ni, Cu, Ga, Zr and Hf, especially one or more of Cr, Mn, Co and Ni.
Suitable conductive supports are for example commercially available conductive carbons. Supports may be specifically prepared for this application.
Preferred carbons may be selected from the oil furnace carbon blacks or acetylene blacks. They may be used as prepared commercially, or specifically treated to increase their graphitic character.
Preferred gold loadings are in the range 0.1 to 1 wt% of the total catalyst weight.
In a method for the manufacture of the novel electrocatalyst material of the invention, one or more compounds of gold may be added to a slurry of an existing WO 94/24710 r PCTlGB94/00835 Pt catalyst material to obtain the electrocatalyst material. The method may comprise the steps of the addition of at least one compound of gold to a slurry of a platinum catalyst, followed by reduction of the gold. The method involves the preformation of the electrode followed by the retrospective deposition of gold rather than the co-deposition of platinum and gold. The platinum is in a reduced statewptior to the addition of a gold L
precursor. A chemical reducing agent is used to reduce the gold.
In some instances small amounts of rhodium such as 0.05 to O. Swt% may advantageously be added with the gold.
The electrocatalyst material of the present invention may be prepared by a number of methods, known to those skilled in the art of catalysis.
An electrode employing the electrocatalyst material of the present invention demonstrates unexpectedly superior performance compared to equivalent electrodes employing' electrocatalyst materials not comprising gold. In particular, performance over a wide range of test conditions, including with different carbon support materials, is demonstrated.
An added advantage of the use of the electrocatalyst materials of the present invention is believed to be improved control of the water content of the fuel cell catalyst. We believe gold provides this control more efficiently than the commonly used hydrophobic polymers, such as polytetrafluoroethylene (PTFE), which is used in WO 94/24710 ' PCT/GB94/00835 S
electrode manufacture both to bind the electrocatalyst material and to make it hydrophobic.
Problems associated with the use of PTFE include its inability to protect ' 5 all catalyst sites, especially those in small pores, and the danger that it may mask active catalytic sites. Since gold can be deposited as very small nuclei, of the same size as the active catalyst (eg 10.1 ~~ diameter), it is able to penetrate into the pores of the catalyst and therefore, we believe, provides more efficient control of the catalyst water content.
The electrocatalyst materials described here will be of use in the phosphoric acid fuel cell (PAFC) and in the other acid electrolyte fuel cells, for example in the solid polymer fuel cell (SPFC), also known as the proton exchange membrane fwel cell (PEMFC), in which the electrolyte comprises a solid proton-conducting polymer membrane commonly based on perfluorosulphonic acid materials. The materials described here will also be of use other acid electrolyte environments in addition to the acid electrolyte fuel cell.
The electrocatalyst materials of the present invention will now be described by Example.
Hereinafter, we shall use the terms "activity" and "performance" as defined below. Hydrophobic electrodes are prepared by mixing the catalyst with PTFE, applying to a wet-proofed carbon paper and sintering as is usually practised in the art.
Activity and performance are measured in a half cell using air and oxygen as reactants.
_z~6o~~g WO 94/24710 . ~ - PCT/GB94/00835 The measurements are made at 180°C, atmospheric pressure and in 100%
phosphoric acid electrolyte. Activity is a measure of the oxygen reduction ability per unit weight of the platinum present, and is measured by the current flow through the electrode at an IR
(Internal Resistance)-free potential of 900mV, versus a Dynamic Hydrogen Electrode (DHE), with oxygen as reactant, and is expressed, iii terms of milliamps per millligram of platinum present. In practice, PAFC cathodes=operate using air as oxidant gas, and :., at high current densities (greater than 100mA/cm2). For electrode performance measurement we quote the IR-free electrode potential at 200mA/cm2 with air as the oxidant.
Comparative Example Pt lO.Owt%, Ni 3.Owt%, on XC72R Carbon (XC72R carbon is a furnace black carbon available from Cabot Europe Ltd, Neuilly sur Seine, France.) XC72R (87g) was added to 6 litres of demineralised water (pH = 6.0) at 60 ° C with stirring. The slurry was maintained at 65 ° C for 30 minutes. Sodium bicarbonate solution (31.98 in 200cm3H20) was added and the temperature increased to 98°C and maintained for 30 mirwtes. Chloroplatinic acid (lOg Pt equivalent dissolved in 200cm3 H20) was added to the slurry via a peristaltic pump over 10 minutes.
NC12.6H20 (3g = Ni in 200cm3 H20) was then added via the peristaltic pump over 10 minutes, and the slurry boiled for a further 2 hours.
The slurry was allowed to cool to 90 ° C and a formaldehyde solution (1% v/v, 280cm3) was added from a peristaltic pump over 10 minutes. The slurry was further boiled for 1 hour, after which it was cooled to 90 ° C and filtered. The filtrate was washed free of soluble chloride ion with demineralised water.
The filtrate cake was dried overnight in an air oven at 105 ° C and crushed with a mortar and pestle.
The material was then heated to a temperature of 930 ° C in a flowing nitrogen atmosphere and maintained at this temperature for 60 minutes to form the alloy.
This gave a catalyst with a nominal composition of lOwt% Pt, 3wt% Ni and a Pt:Ni atomic ratio of 50:50.
romoarative Example Pt/Ni lO.Owt% on Shawinigan carbon (Shawinigan carbon is an acetylene black carbon available from Chevron Chemicals, Houston, Texas, USA.) WO 94/24710 _ PCT/GB94/00835 The preparation in Example 1 was repeated but with 87g Shawinigan carbon instead of XC72R.
>, ~,~[g Pt 10.0%, Ni 3.0%, Au 1;:0Q/o on XC72R carbon The method as described in Example 1 was used to prepare a Pt/Ni catalyst at lOwt% Pt loading. 24.75g of this catalyst was added to 6 litres of preheated (60 ° C) demineralised water (pH 6.0) and the resultant slurry maintained at 60 ° C for 30 minutes. NaHC03 (0.43g) was dissolved in H20 (150cm3) and added to the slurry via a peristaltic pump, over 10 minutes and the slurry was brought to boil.
This condition was maintained for 30 minutes at 100°C. HAuCl4 (0.258 Au metal equivalent), dissolved in 200cm3 H20, was added via a peristaltic pump over 10 minutes.
The slurry was boiled for a further 2 hours and then allowed to cool.
Formaldehyde solution, (7cm3, 1% v/v) was added via a peristaltic pump at -80°C. The slurry was then boiled for a further 1 hour after which it was cooled to 90 ° C, filtered and washed free of soluble chloride ion with demineralised water. The filtrate cake was dried overnight in an air oven at 105°C and crushed with a mortar and pestle.
This gave a catalyst with a nominal composition of lO.Owt% Pt, 3.Owt% Ni, and l.Owt% Au.
WO 94/24710 w ~ g 1 ~ PCT/GB94/00835 9 ' Examul~
Pt lO.Owt%, Ni 3.Owt%, Au l.Owt% on Shawinigan carbon The method as described in Example 2 was used to prepare a Pt/Ni ( l Owt% Pt) catalyst. The method as described in Example 3 was then used with this material to prepare a Pt/Ni/Au catalyst.
The activity of the Pt/Ni/Au catalysts for both types of carbon support demonstrated an unexpected increase in performance as shown by standard half cell polarisation measurements (Figures 1 and 2). Activity and performance data are collated in Table 1.
Example Formulation Nominal Activity Performance No. Loading mA/mg Pt mV at wt% on OZ 200mA/cm2 Pt, Ni, Au on air 1 Pt/Ni/XC72R 10, 3, 48.9 728 2 Pt/Ni/Sh 10, 3, 49.4 737 3 PtJN'>/Au/XC72R 10, 3, 51.7 741 4 Pt/Ni/Au/Sh 10, 3, 58.0 748 _216071 .
WO 94/24710 . PCT/GB94I00835 The activity and performance of the prior art catalysts, as exemplified in Examples 1 and 2 demonstrate activity and performance trends which are typical of those expected for platinum alloy catalysts (see, for example, F J Luczak and D A Landsman in USP 4,447,506).
S ~}"
It can be readily seen that the matecial's'.~of the invention, comprising Au addition to the alloy catalysts (Examples 3 and,~~')~ demonstrate improved activity and performance over the prior art materials.
A CONDUCTIVE SUPPORT
This invention concerns an improved catalyst material, and in particular an improved electrocatalyst material for use in acid electrolyte fuel cell.
In the art of fuel cells, there have been very many proposals for the production of electrocatalysts which are used to coat one or both of the electrodes. It is useful to recall that in a fuel cell, a fuel, which may be hydrogen, a hydrocarbon or an oxygen-containing fuel such as methanol, is oxidised at a fuel electrode (anode) and oxygen is reduced at the cathode. An electrolyte contacts the electrodes, and may be alkaline or acidic, liquid or solid. The phosphoric acid fuel cell (PAFC) is the type of fuel cell closest to commercialisation and there are a number of demonstration units, especially in Japan where there are considerable economic and environmental pressures to reduce imports of hydrocarbon fuels and to cut polluting emissions from power generation. Many people consider that fuel cells are, however, unlikely to get beyond the demonstration stage, because the power output is too low for the capital costs involved. In the PAFC, power output is limited in part by the activity of the cathode catalyst. Increasing cathode catalyst activity can result in higher power density at the same efficiency. 'the capital cost per unit of power is therefore reduced in proportion to the increase in performance. Because the cost of the cathode catalyst is only a fraction of the cost of the fuel cell stack, increasing the power density of the stack reduces the capital cost per unit power out of all proportion to the value of the catalyst per se. It is therefore widely recognised that a cathode catalyst with improved performance would have great value in reducing overall capital cost per unit power.
We have found, surprisingly, that the addition of gold to an existing electrocatalyst, used in an acid electrolyte fuel cell, gives an improved performance catalyst. Previously, gold has been considered ineffective as an electrocatalysf under acid conditions, mainly because of the weakness of the metal-oxygen bond strength.
(See, for example, "Fuel Cell Handbook", Eds A J Appleby and F R Foulkes, p 383, Van Norstrand Reinhold, NY (1989) and US Patent No 3,223,556.) The present invention provides an electrocatalyst material for use in an acid electrolyte environment, comprising platinum alloyed with at least one alloying element and gold, supported on a conductive support, the atomic ratio of platinum to the alloying element being in the range 80:20 to 20:80, and wherein the gold is present in a loading of 0.0001 up to but not including 3wt% of the total catalyst weight.
WO 94/24710 _ ~ ~ PCT/GB94/00835 3 .,'~, ,..
This invention also provides an electrode for use in an acid electrolyte environment containing the electrocatalyst of the present invention.
Yet fiuther, this invention provides an acid electrolyte fuel cell employing the electrocatalyst material of the present invention.
Where the electrocaialyst material comprises a platinum alloy, preferably the alloying elements) are selected from the transition metals, more preferably from Groups IVB, VIB, VIIB, VIII, IB and IIIA of the Periodic Table in "Handbook of Chemistry and Physics"; 64th Edition, CRC Press. Even more preferably, the alloying elements are selected from one or more of Ti, Cr, Mn, Fe, Co, Ni, Cu, Ga, Zr and Hf, especially one or more of Cr, Mn, Co and Ni.
Suitable conductive supports are for example commercially available conductive carbons. Supports may be specifically prepared for this application.
Preferred carbons may be selected from the oil furnace carbon blacks or acetylene blacks. They may be used as prepared commercially, or specifically treated to increase their graphitic character.
Preferred gold loadings are in the range 0.1 to 1 wt% of the total catalyst weight.
In a method for the manufacture of the novel electrocatalyst material of the invention, one or more compounds of gold may be added to a slurry of an existing WO 94/24710 r PCTlGB94/00835 Pt catalyst material to obtain the electrocatalyst material. The method may comprise the steps of the addition of at least one compound of gold to a slurry of a platinum catalyst, followed by reduction of the gold. The method involves the preformation of the electrode followed by the retrospective deposition of gold rather than the co-deposition of platinum and gold. The platinum is in a reduced statewptior to the addition of a gold L
precursor. A chemical reducing agent is used to reduce the gold.
In some instances small amounts of rhodium such as 0.05 to O. Swt% may advantageously be added with the gold.
The electrocatalyst material of the present invention may be prepared by a number of methods, known to those skilled in the art of catalysis.
An electrode employing the electrocatalyst material of the present invention demonstrates unexpectedly superior performance compared to equivalent electrodes employing' electrocatalyst materials not comprising gold. In particular, performance over a wide range of test conditions, including with different carbon support materials, is demonstrated.
An added advantage of the use of the electrocatalyst materials of the present invention is believed to be improved control of the water content of the fuel cell catalyst. We believe gold provides this control more efficiently than the commonly used hydrophobic polymers, such as polytetrafluoroethylene (PTFE), which is used in WO 94/24710 ' PCT/GB94/00835 S
electrode manufacture both to bind the electrocatalyst material and to make it hydrophobic.
Problems associated with the use of PTFE include its inability to protect ' 5 all catalyst sites, especially those in small pores, and the danger that it may mask active catalytic sites. Since gold can be deposited as very small nuclei, of the same size as the active catalyst (eg 10.1 ~~ diameter), it is able to penetrate into the pores of the catalyst and therefore, we believe, provides more efficient control of the catalyst water content.
The electrocatalyst materials described here will be of use in the phosphoric acid fuel cell (PAFC) and in the other acid electrolyte fuel cells, for example in the solid polymer fuel cell (SPFC), also known as the proton exchange membrane fwel cell (PEMFC), in which the electrolyte comprises a solid proton-conducting polymer membrane commonly based on perfluorosulphonic acid materials. The materials described here will also be of use other acid electrolyte environments in addition to the acid electrolyte fuel cell.
The electrocatalyst materials of the present invention will now be described by Example.
Hereinafter, we shall use the terms "activity" and "performance" as defined below. Hydrophobic electrodes are prepared by mixing the catalyst with PTFE, applying to a wet-proofed carbon paper and sintering as is usually practised in the art.
Activity and performance are measured in a half cell using air and oxygen as reactants.
_z~6o~~g WO 94/24710 . ~ - PCT/GB94/00835 The measurements are made at 180°C, atmospheric pressure and in 100%
phosphoric acid electrolyte. Activity is a measure of the oxygen reduction ability per unit weight of the platinum present, and is measured by the current flow through the electrode at an IR
(Internal Resistance)-free potential of 900mV, versus a Dynamic Hydrogen Electrode (DHE), with oxygen as reactant, and is expressed, iii terms of milliamps per millligram of platinum present. In practice, PAFC cathodes=operate using air as oxidant gas, and :., at high current densities (greater than 100mA/cm2). For electrode performance measurement we quote the IR-free electrode potential at 200mA/cm2 with air as the oxidant.
Comparative Example Pt lO.Owt%, Ni 3.Owt%, on XC72R Carbon (XC72R carbon is a furnace black carbon available from Cabot Europe Ltd, Neuilly sur Seine, France.) XC72R (87g) was added to 6 litres of demineralised water (pH = 6.0) at 60 ° C with stirring. The slurry was maintained at 65 ° C for 30 minutes. Sodium bicarbonate solution (31.98 in 200cm3H20) was added and the temperature increased to 98°C and maintained for 30 mirwtes. Chloroplatinic acid (lOg Pt equivalent dissolved in 200cm3 H20) was added to the slurry via a peristaltic pump over 10 minutes.
NC12.6H20 (3g = Ni in 200cm3 H20) was then added via the peristaltic pump over 10 minutes, and the slurry boiled for a further 2 hours.
The slurry was allowed to cool to 90 ° C and a formaldehyde solution (1% v/v, 280cm3) was added from a peristaltic pump over 10 minutes. The slurry was further boiled for 1 hour, after which it was cooled to 90 ° C and filtered. The filtrate was washed free of soluble chloride ion with demineralised water.
The filtrate cake was dried overnight in an air oven at 105 ° C and crushed with a mortar and pestle.
The material was then heated to a temperature of 930 ° C in a flowing nitrogen atmosphere and maintained at this temperature for 60 minutes to form the alloy.
This gave a catalyst with a nominal composition of lOwt% Pt, 3wt% Ni and a Pt:Ni atomic ratio of 50:50.
romoarative Example Pt/Ni lO.Owt% on Shawinigan carbon (Shawinigan carbon is an acetylene black carbon available from Chevron Chemicals, Houston, Texas, USA.) WO 94/24710 _ PCT/GB94/00835 The preparation in Example 1 was repeated but with 87g Shawinigan carbon instead of XC72R.
>, ~,~[g Pt 10.0%, Ni 3.0%, Au 1;:0Q/o on XC72R carbon The method as described in Example 1 was used to prepare a Pt/Ni catalyst at lOwt% Pt loading. 24.75g of this catalyst was added to 6 litres of preheated (60 ° C) demineralised water (pH 6.0) and the resultant slurry maintained at 60 ° C for 30 minutes. NaHC03 (0.43g) was dissolved in H20 (150cm3) and added to the slurry via a peristaltic pump, over 10 minutes and the slurry was brought to boil.
This condition was maintained for 30 minutes at 100°C. HAuCl4 (0.258 Au metal equivalent), dissolved in 200cm3 H20, was added via a peristaltic pump over 10 minutes.
The slurry was boiled for a further 2 hours and then allowed to cool.
Formaldehyde solution, (7cm3, 1% v/v) was added via a peristaltic pump at -80°C. The slurry was then boiled for a further 1 hour after which it was cooled to 90 ° C, filtered and washed free of soluble chloride ion with demineralised water. The filtrate cake was dried overnight in an air oven at 105°C and crushed with a mortar and pestle.
This gave a catalyst with a nominal composition of lO.Owt% Pt, 3.Owt% Ni, and l.Owt% Au.
WO 94/24710 w ~ g 1 ~ PCT/GB94/00835 9 ' Examul~
Pt lO.Owt%, Ni 3.Owt%, Au l.Owt% on Shawinigan carbon The method as described in Example 2 was used to prepare a Pt/Ni ( l Owt% Pt) catalyst. The method as described in Example 3 was then used with this material to prepare a Pt/Ni/Au catalyst.
The activity of the Pt/Ni/Au catalysts for both types of carbon support demonstrated an unexpected increase in performance as shown by standard half cell polarisation measurements (Figures 1 and 2). Activity and performance data are collated in Table 1.
Example Formulation Nominal Activity Performance No. Loading mA/mg Pt mV at wt% on OZ 200mA/cm2 Pt, Ni, Au on air 1 Pt/Ni/XC72R 10, 3, 48.9 728 2 Pt/Ni/Sh 10, 3, 49.4 737 3 PtJN'>/Au/XC72R 10, 3, 51.7 741 4 Pt/Ni/Au/Sh 10, 3, 58.0 748 _216071 .
WO 94/24710 . PCT/GB94I00835 The activity and performance of the prior art catalysts, as exemplified in Examples 1 and 2 demonstrate activity and performance trends which are typical of those expected for platinum alloy catalysts (see, for example, F J Luczak and D A Landsman in USP 4,447,506).
S ~}"
It can be readily seen that the matecial's'.~of the invention, comprising Au addition to the alloy catalysts (Examples 3 and,~~')~ demonstrate improved activity and performance over the prior art materials.
Claims (9)
1. An electrocatalyst material for use in an acid electrolyte environment, comprising platinum alloyed with at least one alloying element and gold which is unalloyed with the platinum, supported on a conductive support, the atomic ratio of platinum to the alloying element being in the range 80:20 to 20:80, and wherein the gold is present in a loading of 0.0001 up to but not including 3wt% of the total catalyst weight.
2. An electrocatalyst material according to claim 1, wherein the alloying element is one or more selected from groups IVB, VIB, VIIB, VIII, IB and IIIA of the Periodic Table.
3. An electrocatalyst material according to claim 2, wherein the alloying element is one or more of Ti, Cr, Mn, Fe, Co, Ni, Cu, Zr and Hf.
4. An electrocatalyst material according to claim 3, wherein the alloying element is one or more of Cr, Mn, Co and Ni.
5. An electrocatalyst material according to claim 4, wherein the alloying element is Ni.
6. An electrocatalyst material according to any one of claims 1 to 5, further comprising 0.05 to 0.5wt% rhodium which is unalloyed with the platinum.
7. An electrode comprising an electrocatalyst material according to any one of claims 1 to 6.
8. An acid electrolyte fuel cell comprising, as the electrocatalyst, the electrocatalyst material of any one of claims 1-4.
9. A method of manufacture of an electrocatalyst according to any one of claims 1 to 8, for use in an acid electrolyte environment comprising the steps of the addition of at least one compound of gold to a slurry of a platinum catalyst, followed by reduction of the gold.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9308094.3 | 1993-04-20 | ||
| GB939308094A GB9308094D0 (en) | 1993-04-20 | 1993-04-20 | Improved catalyst material |
| PCT/GB1994/000835 WO1994024710A1 (en) | 1993-04-20 | 1994-04-20 | Electrocatalyst material comprising a platinum alloy or a conductive support |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2160718A1 CA2160718A1 (en) | 1994-10-27 |
| CA2160718C true CA2160718C (en) | 2005-03-22 |
Family
ID=10734117
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002160718A Expired - Fee Related CA2160718C (en) | 1993-04-20 | 1994-04-20 | Electrocatalyst material comprising a platinum alloy on a conductive support |
Country Status (7)
| Country | Link |
|---|---|
| EP (1) | EP0698299B1 (en) |
| JP (1) | JP3512802B2 (en) |
| AT (1) | ATE153479T1 (en) |
| CA (1) | CA2160718C (en) |
| DE (1) | DE69403334T2 (en) |
| GB (1) | GB9308094D0 (en) |
| WO (1) | WO1994024710A1 (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5916702A (en) * | 1997-08-15 | 1999-06-29 | Exxon Research And Engineering Co. | CO tolerant platinum-zinc fuel cell electrode |
| US7201993B2 (en) | 2000-08-04 | 2007-04-10 | Matsushita Electric Industrial Co., Ltd. | Polymer electrolyte fuel cell |
| JP2003331855A (en) * | 2002-05-16 | 2003-11-21 | Tokyo Inst Of Technol | Cathode electrocatalyst for polymer electrolyte fuel cell and polymer electrolyte fuel cell |
| JP2006526880A (en) * | 2003-05-30 | 2006-11-24 | イー・アイ・デュポン・ドウ・ヌムール・アンド・カンパニー | Components using fuel cells and their high metal-to-support ratio catalysts |
| GB0419062D0 (en) | 2004-08-27 | 2004-09-29 | Johnson Matthey Plc | Platinum alloy catalyst |
| US20060280997A1 (en) * | 2005-03-09 | 2006-12-14 | Samsung Sdi Co., Ltd. | PtNi based supported electrocatalyst for proton exchange membrane fuel cell having CO tolerance |
| KR20190076999A (en) * | 2016-10-26 | 2019-07-02 | 쓰리엠 이노베이티브 프로퍼티즈 캄파니 | catalyst |
| EP3533097B1 (en) * | 2016-10-26 | 2021-04-21 | 3M Innovative Properties Company | Catalyst |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1047933A (en) * | 1962-09-12 | 1966-11-09 | Exxon Research Engineering Co | Catalysts |
| US3933684A (en) * | 1972-01-03 | 1976-01-20 | Prototech Company | Method of forming palladium oxide and palladium particles |
| US5068161A (en) * | 1990-03-30 | 1991-11-26 | Johnson Matthey Public Limited Company | Catalyst material |
| JPH04141236A (en) * | 1990-09-29 | 1992-05-14 | Stonehard Assoc Inc | Platinoid catalyst and its manufacturing process |
-
1993
- 1993-04-20 GB GB939308094A patent/GB9308094D0/en active Pending
-
1994
- 1994-04-20 DE DE69403334T patent/DE69403334T2/en not_active Expired - Lifetime
- 1994-04-20 WO PCT/GB1994/000835 patent/WO1994024710A1/en not_active Ceased
- 1994-04-20 AT AT94912653T patent/ATE153479T1/en active
- 1994-04-20 CA CA002160718A patent/CA2160718C/en not_active Expired - Fee Related
- 1994-04-20 EP EP94912653A patent/EP0698299B1/en not_active Expired - Lifetime
- 1994-04-20 JP JP52293394A patent/JP3512802B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| ATE153479T1 (en) | 1997-06-15 |
| EP0698299A1 (en) | 1996-02-28 |
| DE69403334D1 (en) | 1997-06-26 |
| JP3512802B2 (en) | 2004-03-31 |
| EP0698299B1 (en) | 1997-05-21 |
| JPH08509094A (en) | 1996-09-24 |
| CA2160718A1 (en) | 1994-10-27 |
| DE69403334T2 (en) | 1997-10-23 |
| WO1994024710A1 (en) | 1994-10-27 |
| GB9308094D0 (en) | 1993-06-02 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US5759944A (en) | Catalyst material | |
| CA2039464C (en) | Platinum containing electrocatalyst material | |
| Li et al. | Nano-stuctured Pt–Fe/C as cathode catalyst in direct methanol fuel cell | |
| US5939220A (en) | Catalyst | |
| EP0577291B1 (en) | Process for the preparation of electrode assemblies | |
| JP4401059B2 (en) | Process for preparing anode catalyst for fuel cell and anode catalyst prepared using the process | |
| CN1189966C (en) | Improved composition of a selective oxidation catalyst for use in fuel cells | |
| KR101797782B1 (en) | Catalyst with metal oxide doping for fuel cells | |
| Lee et al. | IrxCo1− x (x= 0.3–1.0) alloy electrocatalysts, catalytic activities, and methanol tolerance in oxygen reduction reaction | |
| CA2468262A1 (en) | Supported nanoparticle catalyst | |
| CA2458579A1 (en) | Ternary anode electrocatalysts for coated substrates used in fuel cells | |
| CA2666634A1 (en) | Catalyst support for fuel cell | |
| GB2242203A (en) | Catalyst material comprising platinum alloy supported on carbon | |
| Choudhary et al. | Synthesis of low-cost HNO3-functionalized acetylene black carbon supported Pt-Ru/C AB nano electrocatalysts for the application in direct ethanol fuel cell (DEFC) | |
| EP0899348B1 (en) | Co-tolerant platinum-zinc alloy suitable for use in a fuel cell electrode | |
| Reyes-Rodríguez et al. | Tailoring the morphology of Ni–Pt nanocatalysts through the variation of oleylamine and oleic acid: a study on oxygen reduction from synthesis to fuel cell application | |
| CA2160718C (en) | Electrocatalyst material comprising a platinum alloy on a conductive support | |
| WO2006046453A1 (en) | Electrode catalyst for fuel cell and fuel cell | |
| Gôtz et al. | Screening binary and ternary catalyst formulations for direct-methanol-PEM fuel cells | |
| Götz | Petersenstrasse 20, 64287 Darmstadt, Germany | |
| Golikand et al. | Gas Diffusion Electrodes for Direct Methanol Fuel Cells using Methanol-Resistant Catalyst | |
| Energy | Hydro-Quebec assisted in meeting the publication costs of this article. | |
| HK1018630B (en) | Co-tolerant platinum-zinc alloy suitable for use in a fuel cell electrode |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |