3D hierarchical porous Fe, N‐doped hollow carbon nano‐spheres (Fe−N−C HPNCs) as efficient ORR electrocatalyst were obtained using melamine‐formaldehyde resin (MF) nanospheres as thermal sacrificial hard template to optimize the pore structure and provide nitrogen source to the catalyst. The optimized Fe−N−C HPNCs catalyst exhibited excellent catalytic activity with onset (Eonset) and half‐wave (E1/2) potential (Eonset=1.07 V; E1/2=0.90 V vs. RHE) superior to commercial Pt/C catalyst in 0.1 M KOH solution, and demonstrated excellent stability. When applied as cathode electro‐catalyst in a Zn‐air battery, it produced maximum power density (Pmax) of 127 mW cm−2, which is higher than that of commercial Pt/C (Pmax=119 mW cm−2). It also showed good activity (Eonset=0.89 V; E1/2=0.78 V) in 0.1 M HClO4 electrolyte with significantly enhanced stability (ΔE1/2=−7 mV) relative to the Pt/C catalyst (ΔE1/2=−27 mV).
Zn‐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.
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