CONTAMINATION-TOLERANT ANODES FOR PROTON EXCHANGE MEMBRANE FUEL CELLS

THERE IS A RENEWED INTEREST IN FUEL CELLS AS PRIMARY POWER SOURCES FOR ELECTRIC VEHICLES. THE ACIDIC PROTON EXCHANGE MEMBRANE FUEL CELL OPERATES AT A MAXIMUM TEMPERATURE OF 95 DEGREES CENTIGRADE AND, AT PRESENT, RELIES ON THE USE OF PLATINUM-BASED ELECTROCATALYSTS. FOR ACID FUEL CELLS OPERATING AT TEMPERATURES BELOW 130 DEGREES CENTIGRADE, HYDROGEN IS THE MOST ACTIVE COMMON FUEL THAT CAN BE USED. HOWEVER, TO BE OF PRACTICAL USE FOR POWER GENERATION, A FUEL CELL MUST BE CAPABLE OF USING AN AVAILABLE FUEL, SUCH AS METHANOL OR NATURAL GAS. FOR TRANSPORTATION APPLICATIONS, IT HAS BEEN PROPOSED THAT THE HYDROGEN REQUIRED FOR PROTON EXCHANGE MEMBRANE FUEL CELLS WILL BE PRODUCED BY THE STEAM REFORMING OF METHANOL. HOWEVER, THE STEAM REFORMING OF METHANOL RESULTS IN THE PRODUCTION OF LOW LEVELS OF CARBON MONOXIDE. THE PRESENCE OF CARBON MONOXIDE AND TRACE CONTAMINANTS, SUCH AS FORMALDEHYDE, ACETALDEHYDE, FORMIC ACID, AND ACETIC ACID IN THE HYDROGEN FUEL GAS STREAM SEVERELY DEGRADES THE PERFORMANCE OF PROTON EXCHANGE MEMBRANE FUEL CELLS, SINCE CARBON MONOXIDE ACTA AS A POISON TO PLATINUM ELECTRODES OPERATING IN THE RANGE OF POTENTIALS, 0-0.5 V (NORMAL HYDROGEN ELECTRODE), AT TEMPERATURES LESS THAN 130 DEGREES CENTIGRADE IN ACIDIC ELECTROLYTES. IN ADDITION TO SELECTIVE CATALYTIC OXIDATION OF CARBON MONOXIDE IN THE REFORMER OUTPUT, A NUMBER OF OTHER METHODS HAVE BEEN CONSIDERED. AN ALTERNATIVE APPROACH TO AVOID THE DEGRADATION IN PERFORMANCE OF PROTEN EXCHANGE MEMBRANE FUEL CELLS BY CARBON MONOXIDE AND OTHER SMALL ORGANIC MOLECULE CONTAMINANTS, IS TO DEVELOP CONTAMINATION-TOLERANT ANODES FOR USE IN THIS FUEL CELL SYSTEM. THUS, THE GOAL OF THIS PROJECT IS TO OVERCOME TO POISONING PROBLEMS ENCOUNTERED IN USING PLATINUM METAL-BASED ELECTROCATALYSTS IN PROTON EXCHANGE MEMBRANE FUEL CELLS SUPPLIED WITH HYDROGEN FUEL DERIVED FROM STEAM-REFORMED METHANOL. PHASE I WILL INVESTIGATE THE FEASIBILITY OF USING NOVEL METAL OXIDE ANODES WHICH ARE NOT SENSITIVE TO THE PRESENCE OF SMALL ORGANIC MOLECULE CONTAMINANTS OR OTHER IMPURITIES FOR THE OXIDATION OF HYDROGEN GAS. IT IS ONLY RECENTLY THAT METAL OXIDE ELECTRODES HAVE BEEN USED FOR HYDROGEN EVOLUTION AS WELL AS HYDROGEN OXIDATION IN ACIDIC AND SOLUTIONS.