Enhancing the Stability of a Pt-Free ORR Catalyst via Reaction Intermediates

Abstract

Finding a platinum-free cathode catalyst that effectively models the oxygen reduction reaction (ORR) of a proton-exchange membrane (PEM) fuel cell cathode better than the current commercial Pt/C catalyst has been a major shortcoming in fuel cell technology. Overall, a promising platinum-free cathode catalyst must offer great ORR activity, ORR selectivity, and acid stability. Due to their enticing ORR activity and selectivity to the preferred four-electron ORR pathway, the possible dissolution reactions and oxygen-intermediate reactions of iron phthalocyanine monolayer supported on a pristine graphene (GFePc) and boron-doped graphene substrate (BGFePc) have been studied to determine the stability as a function of potential and pH through spin-polarized density functional theory (DFT) calculations at both infinitesimally low (10−9m) and 1 m Fe2+/Fe3+ ionic concentrations. BGFePc offers higher stability in both concentrations than GFePc. In both cases, the oxygen-intermediates are more stable than the bare catalytic surface due to the metal d-band center shifting further away from the Fermi level in the valence band state (higher energy of antibonding). Moreover, at an Fe2+ ionic concentration, both catalysts would be stable in the potential and pH regions at the operating conditions of rotating disk electrode (RDE) experiments and PEM fuel cells.