F‐Doped Co−N−C Catalysts for Enhancing the Oxygen Reduction Reaction in Zn‐Air Batteries

Abstract

AbstractZn‐air battery is a promising next‐generation energy storage device. Its performance, however, is limited by a high overpotential resulted from the slow kinetics of the cathodic oxygen reduction reaction (ORR). This study reports a simple strategy for preparation of a fluorine‐doped Co−N−C composite as highly efficient electrocatalyst for ORR. The C@PVI‐(TPFC)Co‐800 catalyst was prepared by pyrolysis of F‐containing Co‐corrole that was assembled on PVI‐functionalized carbon black through the axial imidazole coordination (PVI=polyvinylimidazole, TPFC=5,10,15‐triperfluorophenyl‐21H, 22H‐corrole). The C@PVI‐(TPFC)Co‐800 catalyst exhibited much more positive ORR half‐wave potential (E1/2=0.88 V vs. RHE) than its counterpart C@PVI‐(TPC)Co‐800 (E1/2=0.82 V, TPC=5,10,15‐triphenyl‐21H, 22H‐corrole) without F‐doping in 0.1 M KOH electrolyte. C@PVI‐(TPFC)Co‐800 also achieved a greater kinetic current density and enhanced durability in alkaline media. In addition, a Zn‐air battery with C@PVI‐(TPFC)Co‐800 loaded at the cathode delivered much higher peak power density (Pmax=141 mW/cm2) and open‐circuit voltage (OCV=1.45 V) over the C@PVI‐(TPC)Co‐800 counterpart (Pmax=110 mW/cm2, OCV=1.39 V) and the commercial 20 % Pt/C (Pmax=119 mW/cm2, OCV=1.42 V) as well. The promoted catalyst performance for ORR was attributed to the increased specific surface area, more defects generated, and reduced electron density distribution around the Co metal center after F‐doping.