Location effects of the catalysts in cathode of proton exchange membrane fuel cells

A steady, two-dimensional model of the cathode catalyst layer in a Proton Exchange Membrane Fuel Cell was presented by taking into account the local geometric effects of the catalysts. The equations of the model refer to the oxygen diffusion in the gas pores of the cathode catalyst layer and in the electrolyte phase, the oxygen distribution at the gas/electrolyte interface, the proton transport in the electrolyte and the electrochemical reaction kinetics, respectively. Those differential equations of the model were solved by the finite element method. The simulation results indicate that the oxygen transport in the cathode catalyst layer is significantly dependent on the catalyst location. As the catalyst continuously penetrates into the electrolyte, oxygen transport is firstly enhanced then decreased rapidly. The effect of catalyst location on the proton migration in electrolyte is similar to that on oxygen diffusion, but is less prominent. From the comparison of electrochemical performance for catalysts at different locations it is found that the optimum location of cathode catalyst is at the location where the catalyst is just completely covered by the electrolyte.