Synergistic effects of fluorine and nitrogen dopants in fluorine/nitrogen-coordinated iron-co-doped carbon catalysts for enhanced oxygen reduction in alkaline media

Abstract

The expensiveness of oxygen reduction reaction (ORR) catalyst materials especially Pt has hindered the commercialization of next-generation energy conversion devices including metal-air batteries and polymer electrolyte membrane fuel cells. Fe-N-C has drawn attention as a nonprecious metal catalyst owing to its high but commercially unsatisfactory ORR performance; nevertheless, additional heteroatom co-doping could help augment its ORR activity. Here we report nitrogen/fluorine-coordinated iron-co-doped carbon (Fe@NFC) catalysts with improved ORR performance in alkaline media. The annealing temperature affects the nitrogen/fluorine doping and functional group formation, as ascertained by an analysis of control samples annealed at various temperatures. To assess the synergy between the doped fluorine and nitrogen-coordinated iron, we compare the catalyst annealed at 700 C (Fe@NFC700) with control samples containing different heteroatom dopants but annealed at 700 C (Fe@NC, Fe@FC). Fe@NFC700 shows improved ORR kinetics and onset potential than those of Fe@NC and commercial Pt/C, respectively, in alkaline media.