PVP-Assisted Iron-Doped ZIF-8 as an Efficient Fe-N-C Oxygen Reduction Electrocatalyst for Zinc-Air Batteries

Transition metal/nitrogen carbon composite (M/NC) is a highly active oxygen reduction reaction (ORR) electrocatalyst, widely used in fuel cells and zinc-air batteries. Herein, a uniform and regular PVP-assisted iron-doped nano dodecahedron (ZP 0.1 F/NC) is prepared by a simple and efficient one-step in-solution reaction, followed by controlled in situ pyrolysis. The synthesized electrocatalyst showed excellent electrocatalytic ORR activity in an alkaline medium. Compared with standard 20% Pt/C electrocatalyst, ZP 0.1 F/NC exhibited onset potential (E onset ) (0.974 V vs 0.967 V), half-wave potential (E 1/2 ) (0.861 V vs 0.857 V) and the limiting current density (j d ) was 6.373 mA cm −2 vs 5.401 mA cm −2 , also better than the Fe doped ZIF-8 nitrogen composite (ZF/NC), PVP auxiliary ZIF-8 (ZP 0.1 /NC) and pure ZIF-8 nitrogen composite (Z/NC) synthesized by the same procedure. In addition, the zinc-air battery assembled with ZP 0.1 F/NC also exhibits outstanding discharge capacity, with a specific capacity and energy density of 793.3 mAh g −1 and 974.9 Wh kg Zn − 1 , respectively, much higher than that of commercial 20% Pt/C-based zinc-air battery (719.8 mAh g −1 , 842.6 Wh kg Zn − 1 ), indicating its great potential in practical energy conversion and storage.