AT THE HEART OF THE PEM FUEL CELL IS THE MEMBRANE ELECTRODE ASSEMBLY (MEA). TODAY, THE MEA IS STILL A MAJOR OBSTACLE FOR COMMERCIALIZATION OF PEMFCS. FUEL CELL PERFORMANCE IS STRONGLY DEPENDENT ON MEA. THE MEA CONSISTS OF A PROTON EXCHANGE MEMBRANE, CATALYST LAYERS, AND GAS DIFFUSION LAYERS (GDL). THE CATALYST LAYER (CL) IS WHERE THE HYDROGEN OXIDATION REACTION (HOR) OR OXYGEN REDUCTION REACTION (ORR) TAKES PLACE. MEMBRANE REFERS TO A THIN LAYER OF ELECTROLYTE WHICH CONDUCTS PROTONS FROM THE ANODE TO THE CATHODE. THE PERFORMANCE OF POLYMER ELECTROLYTE MEMBRANE (PEM) FUEL CELL IS MAINLY INFLUENCED BY OHMIC, ACTIVATION, AND CONCENTRATION OVERPOTENTIALS. THE ACTIVATION OVERPOTENTIAL ORIGINATES FROM THE IRREVERSIBILITY OF THE ELECTROCHEMICAL REACTION. OHMIC OVERPOTENTIAL IS GENERATED BY THE IONIC AND ELECTRONIC CHARGE-TRANSFER RESISTANCES. CONCENTRATION OVERPOTENTIAL IS GENERATED BY MASS TRANSPORT IN THE ELECTRODES. A NUMBER OF STUDIES HAVE SHOWN THAT THE ACTIVATION OVERPOTENTIAL AND THE OHMIC OVERPOTENTIAL WERE RESPONSIBLE FOR MOST OF THE VOLTAGE LOSS. THE ACTIVATION OVERPOTENTIAL EXPRESS VOLTAGE DROPS AT THE CATALYST LAYERS. OHMIC OVERPOTENTIAL IS CAUSED BY THE RESISTANCE OF THE PROTON EXCHANGE MEMBRANE TO THE HYDROGEN IONS TRANSPORTING THROUGH IT. THEREFORE, RESEARCH FOCUSED ON THE CATALYST LAYER AND PROTON EXCHANGE MEMBRANE AS TWO KEY COMPONENTS IN THE DEVELOPMENT OF FUEL CELL TECHNOLOGY. THE OBJECTIVE OF THIS WORK IS TO OUTLINE MAJOR CHALLENGES IN PROTON EXCHANGE MEMBRANE AND ELECTROCATALYST AND THE NEEDS FOR FUNDAMENTAL RESEARCH FOR THE NEAR FUTURE AND PRIOR TO FUEL CELL COMMERCIALIZATION.

NANOCOMPOSITE ORGANIC-INORGANIC MEMBRANES WERE PREPARED WITH HETEROPOLYACIDS (HPAS) AS THE INORGANIC FILLERS. THE MEMBRANE DENSITY, WATER UPTAKE, SWELLING, ION EXCHANGE CAPACITY (IEC) AND THE CONDUCTIVITY OF PREPARED NANOCOMPOSITE MEMBRANES WERE MEASURED AND COMPARED WITH THE PLAIN MEMBRANE. RESULTS SHOWED THAT BY ADDITION OF HPA TO THE POLYMER, THE DENSITY OF MEMBRANES WAS REDUCED, THE WATER UPTAKE WAS INCREASED AND THE SWELLING WAS REDUCED. AS A RESULT, THE IEC OF NANOCOMPOSITE MEMBRANES WAS SLIGHTLY LOWER THAN THE PLAIN POLYMER. THE CONDUCTIVITY OF MEMBRANES IS INCREASING BY THE ADDITION OF HPAS.

CONCERNS DUE TO DEPLETION OF FOSSIL FUEL ENERGIES FROM ONE SIDE AND THEIR MAJOR SHARE IN ENVIRONMENTAL POLLUTIONS ON THE OTHER HAND HAS CHANGED THE EFFICIENCY AND ENERGY CONSUMPTION TOWARD USING HIGH EFFICIENT ELECTRICITY PRODUCTION EQUIPMENTS SUCH AS FUEL CELLS. SINCE THE PRIMARY COSTS OF THESE EQUIPMENTS IS DECREASING EVERY YEAR, THEIR ENTRANCE TO INTERNATIONAL MARKET IS PREDICTABLE. IN THIS WAY, MANY ATTEMPTS HAVE CONDUCTED TOWARD THE OPTIMIZATION OF FUEL CELLS INCLUDING PROTON EXCHANGE MEMBRANE FUEL CELLS (PEMFC).AMONG THE MANY METHODS WE CAN REFER TO NEW HEURISTICS OPTIMIZATION METHODS. IN THIS STUDY THE PROPOSED ALGORITHM IS HARMONY SEARCH ALGORITHM THAT IS ONE OF THE NEW HEURISTICS METHODS. IN COMPARISON TO OTHER ALGORITHMS THAT ARE APPLIED FOR THE OPTIMIZATION PROCESS OF PEMFC’S, THIS ALGORITHM HAS PRESENTED THE BEST RESULTS IN LESS TIME, BUT WE ARE SEARCHING FOR MORE APPROPRIATE ALGORITHMS WITH BETTER AND MORE ACCEPTABLE RESULTS.

THE DEPARTMENT OF ENERGY (DOE) HYDROGEN PROGRAM SUPPORTS RESEARCH AND DEVELOPMENT THAT HAS SUBSTANTIALLY IMPROVED THE STATE-OF-THE-ART IN FUEL CELL TECHNOLOGY, ESPECIALLY WITH REGARD TO THE MAJOR TECHNICAL HURDLES TO FUEL CELL COMMERCIALIZATION - DURABILITY, PERFORMANCE, AND COST OF FUEL CELL COMPONENTS AND SYSTEMS. CATALYST LAYER DEGRADATION HAS BECOME AN IMPORTANT ISSUE IN THE DEVELOPMENT OF PROTON EXCHANGE MEMBRANE FUEL CELLS (PEMFCS). THEIR PERFORMANCE DECREASE DURING OPERATION IS ATTRIBUTED, AMONGST OTHERS, TO THE LOSS OF ELECTROCHEMICAL SURFACE AREA OCCURRING DURING LONG-TERM AGEING. THESE LOSSES ARE MAINLY DUE TO CATALYST METAL DEGRADATION AND CARBON-SUPPORT CORROSION, WHICH ARE CONTINUOUS IRREVERSIBLE PROCESSES THAT CAN DRAMATICALLY REDUCE THE FUEL CELL LIFETIME. THIS PAPER REVIEWS THE MOST RECENT RESEARCH ON DEGRADATION AND DURABILITY ISSUES IN THE CATALYST LAYERS INCLUDING: (1) PLATINUM CATALYSTS, (2) CARBON SUPPORTS, AND (3) NAFION IONOMER AND INTERFACIAL DEGRADATION. THE REVIEW AIMS TO PROVIDE A CLEAR UNDERSTANDING OF THE LINK BETWEEN MICROSTRUCTURAL/MACROSTRUCTURAL CHANGES OF THE CATALYST LAYER AND PERFORMANCE DEGRADATION OF THE PEM FUEL CELL FUELED WITH HYDROGEN.

LARGE NUMBERS OF EXPERIMENTS ARE OFTEN NEEDED TO FIND THE EFFECTS OF THE PARAMETERS ON PERFORMANCE OF PEMFC, BUT IT IS WELL KNOWN THAT PRESSURE AND TEMPERATURE WERE THE EFFECTIVE PARAMETERS IN PERFORMANCE OF FUEL CELL. IN THIS STUDY, THE GENETIC ALGORITHM WAS APPLIED TO DETERMINE WORKING CONDITIONS THAT OBTAINING MAXIMUM POWER DENSITY OF A PEMFC. A QUASI TWO DIMENSIONAL, ISOTHERMAL MODEL WAS USED FOR THE PROTON EXCHANGE MEMBRANE (PEM) FUEL CELL AS FITNESS FUNCTION OF GENETIC ALGORITHM AND EXPERIMENTAL SETUP WAS DEVELOPED TO VALIDATION OF THAT MODELING. AT LAST THE BEST VALUES OF PARAMETERS WERE DETERMINED.