Mechanism of Degradation of Polymer Fuel Cell Cathode Catalyst: Research and Modeling

The article presents a mathematical model of the degradation of the active surface of a platinum catalyst in a hydrogen–air (oxygen) fuel cell with a proton-conducting polymer electrolyte. The mathematical model is a system of integral–differential equations solved by the finite-difference method. The model takes into account the following phenomena: electrochemical dissolution of platinum nanoparticles, particle growth (due to deposition and migration, Ostwald ripening, and coalescence of platinum nanoparticles on the surface of a carbon carrier), diffusion of platinum ions in the ionomer, and their introduction into the membrane. The calculations are performed for two types of platinum catalysts: a commercial monoplatinum system synthesized on carbon black and a catalytic system synthesized on carbon nanotubes. As a result of modeling, data are obtained on the size distribution of the platinum particles and the values of the electrochemically active surface area depending on the time of accelerated stress testing.