Porosity and catalyst utilization of thin layer cathodes in air operated PEM-fuel cells

Better performance of and higher electrocatalyst utilization in proton-exchange membrane fuel cells equipped with thin film electrodes is achieved by exploiting pore forming additives in the electrode recipe formulation. Preparing the membrane-electrode assembly by a hot spraying procedure already provides 35% porosity. Additional coarse porosity is obtained by adding pore formers to the electrocatalyst slurry which is used for the hot spraying process. This allows for a better access of oxygen from air to the depth of the cathode. For air operation at ambient pressure and low catalyst loading of 0.15 mg Pt cm(-2) a current density of 200 mA cm(-2) at 0.7 V cell voltage can be obtained with such electrodes.