Influence of Graded Platinum Loading on the Performance of Proton Exchange Membrane Fuel Cell

Proton exchange membrane fuel cells are among the most promising alternatives to the internal combustion engine. To allow easier commercialization of fuel cell technology in automotive industry, fuel cells should operate at higher current and power densities. Previous studies have shown that by using variable-temperature flow field and/or graded cathode catalyst design positively affects the performance characteristics of fuel cell at higher current densities. In this work, using a computational fluid dynamics software, a numerical model of the fuel cell with linearly graded distribution of platinum loading of cathode catalyst layer is made and compared to the fuel cell with uniformly distributed platinum loading. Results show a clear improvement of the polarization and power density curves at higher current densities where operation of the fuel cell in automotive industry is to be expected. Increase of electric potential reaches as high as 35 % at current density of 2 A cm(-2) for graded platinum loading case. Excessive water being produced at higher current densities is also of importance as it can lead to the flooding of the cell. Decrease in liquid saturation in gas diffusion layer, averaging 5 %, and in channels, averaging 7 %, is also shown for all operating conditions of the fuel cell. All improvements gained have not caused significant worsening of the homogeneity of current density while saving around 19 % of valuable platinum and reducing the overall cost of the fuel cell.