Dynamic modeling of chemical membrane degradation in polymer electrolyte membrane fuel cells: Effect of precipitated Pt particles

Chemical membrane degradation in polymer electrolyte membrane fuel cells operated under real conditions is often accompanied and affected by Pt catalyst degradation. This study investigates the effects of both artificially impregnated Pt particles and Pt migration on chemical membrane degradation are numerically investigated. For the first time, the impact of Pt migration is numerically analyzed. Membrane structural changes with coupled chemical membrane and Pt degradations are proposed. For Pt particles that are artificially impregnated in the membrane, yielding a Pt content of up to 50 mol% Pt, the membrane degrades at the fastest rate at moderate Pt contents (2 mol% Pt). The impregnated Pt particles promote the conversion of Fe3+ to Fe2+, which adversely impacts the membrane durability. The decrease in Pt content leads to reduction in both the Fe2+ conversion time and trend. In comparison, the naturally precipitated Pt particles in the membrane from the degraded Pt catalysts in the CL, have demonstrated a Pt content consistently lower than 2 mol% Pt. As a result, the chemical degradation rate of real fuel cells accelerates significantly with increasing Pt particle concentration. The chemical degradation rate increases with the gas solubility at the pore/electrolyte interface. With higher gas solubility, the peak location of chemical membrane degradation shifts from the anode side to the cathode side.