Kinetic Analysis of Carbon Corrosion-Induced Degradation of Platinum Group Metal-Free Catalysts in Acidic Media

Low-cost and high-activity platinum group metal-free (PGM-free) oxygen reduction reaction (ORR) catalysts are promising for use in polymer electrolyte fuel cells (PEFCs). However, their durability remains a challenge. Herein, we investigate the degradation mechanisms of iron- and nitrogen-doped carbon (Fe–N–C) catalysts and nitrogen-doped carbon (N–C) at 1.0 V vs. RHE, mimicking the open-cell cathode potential in PEFCs. The catalyst oxidation current decreases over time and follows a power-law decay model, indicating competition between surface passivation and carbon corrosion. The ORR activity decays and follows an exponential model with an offset, indicating the coexistence of stable and unstable active sites. Further, we propose that the Fe–Nx edge sites are more susceptible to high potential corrosion than the in-plane sites. These findings point to the susceptibility of carbon matrix in PGM-free catalysts to electrochemical corrosion, revealing likely mechanisms of the ORR activity loss, crucial for developing durable PGM-free catalysts.