Graphitic carbon layer-encapsulated Co nanoparticles embedded on porous carbonized wood as a self-supported chainmail oxygen electrode for rechargeable Zn-air batteries

Abstract

A self-supported chainmail electrocatalyst is developed by embedding graphitic carbon layer-encapsulated Co nanoparticles on N-doped carbonized wood (Co@NCW) as an advanced air cathode for rechargeable Zn-air batteries (ZABs). The NCW with open aligned microchannels facilitates O2 and electrolyte permeation and transportation, while the uniformly distributed graphitic carbon layer-encapsulated Co nanoparticles on NCW featuring fast electron transfer kinetics provide abundant triphase reaction sites for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The Co@NCW exhibits a half-wave potential of 0.89 V vs. reversible hydrogen electrode (RHE) for ORR outperforming the Pt/C (0.85 V vs. RHE) and an overpotential of 410 mV for the OER (10 mA cm−2) comparable to RuO2 (340 mV). A rechargeable ZAB assembled with Co@NCW presents a power density of 47.5 mW cm−2 and excellent stability at 5 mA cm−2 for 240 h. This work provides an effective strategy to fabricate a practically applicable oxygen electrode for ZABs.