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 PROTON EXCHANGE MEMBRANE FUEL CELL (PEMFC) OFFERS AN EXCEPTIONAL POTENTIAL FOR A CLEAN, EFFICIENT, AND RELIABLE POWER SOURCE. THE DIFFERENT OPERATIVE CONDITIONS IN PEMFC SUCH AS PRESSURE, CELL AND GAS TEMPERATURES CAN SUBSTANTIALLY SHIFT THE CELL PERFORMANCE CURVE. THIS PAPER IS AN ATTEMPT TO INVESTIGATE THE EFFECT OF CELL BODY TEMPERATURE, OF H2 AND O2 INLET TEMPERATURE, AND BACK PRESSURE ON SINGLE-CELL PERFORMANCE. IT WAS REVEALED THAT THE HIGHEST PERFORMANCE OF PEMFC IS OPTIMIZED AT CELL BODY TEMPERATURE 80OC. THE BEST H2 AND O2 INLET-TEMPERATURE ARE 65OC AND 55OC, RESPECTIVELY. THE OPTIMIZED BACK-PRESSURE WAS DETERMINED IN 3 BAR. MOREOVER, IN THIS RESEARCH A SINGLE-CELL PEMFC WAS MANUFACTURED AND TESTED IN THE OPTIMIZED CONDITIONS. THE RESULTS SHOWED THE MAXIMUM POWER DENSITY AS HIGH AS 812 MW/CM2 AND CURRENT DENSITY 900 MA/CM2 AT 0.6 V.

EXTENSIVE RESEARCH AND DEVELOPMENT EFFORTS ARE BEING UNDER TAKEN IN RECENT YEAR IN THE FIELD OF PEM FUEL CELL (PEMFC) SYSTEMS TO MAKE THEM COMMERCIALLY VIABLE. IN PROTON EXCHANGE MEMBRANE FUEL CELLS, STABILITY AND DURABILITY ARE IMPORTANT OBJECTS FOR COMMERCIALIZATION. IT IS WELL-KNOWN THAT CATALYST DEGRADATION AND CARBON-SUPPORT CORROSION ARE THE MAIN FACTORS REDUCING STABILITY, AND USING PT NANOCATALYST ON CARBON NANOTUBE SUPPORTS INSTEAD OF PT/C INCREASE STABILITY AND DURABILITY AFTER LONG-TERM AGING. IN THIS WORK, A HYDROTHERMAL METHOD WAS EMPLOYED TO PREPARE PT NANOPARTICLES DISPERSED HIGHLY ON MULTIWALLED CARBON NANOTUBES WITH 19.4 WT. % PT. MEMBRANE ELECTRODE ASSEMBLES (MEAS) FROM TOW CATALYST FABRICATED WITH THIN FILM METHOD. IN FUEL CELL TEST STATION, THE POLARIZATION, AC IMPEDANCE AND CYCLIC VOLTAMMETRY EXPERIMENT OF MEAS AND ALSO ADT TEST WAS DONE. THE PT/C CATALYST SHOWED NO ACTIVITY IN FUEL CELL TESTING AFTER 2000 POTENTIAL CYCLES DUE TO SEVERE CARBON CORROSION, PT DISSOLUTION, AND CATALYST PARTICLE SINTERING. CONVERSELY, THE PT/MWCNT CATALYST SHOWED BETTER ELECTROCHEMICALLY ACTIVE SURFACE AREA AND ALSO DURABILITY AFTER A POTENTIAL CYCLING. THE ANALYSIS OF AC IMPEDANCE SPECTRA ASSOCIATED REVEALED THAT THE PRESENCE OF CNTS SIGNIFICANTLY REDUCED INCREASING OF ACTIVATION RESISTANCES. THE PERFORMANCE OF FRESH MEA FABRICATED FROM PT/C WAS BETTER THAN FRESH PT/MWCNT MEA, BUT AFTER ADT TEST HAD MORE REDUCE. LOSS ELECTROCHEMICAL ACTIVE SURFACE AREA OF PT/C CATALYST WAS HIGHER THAN PT/MWCNT CATALYST DUE TO MORE CATALYST PARTICLE SINTERING.