Cobalt Oxide Nanorods Supported on rGO as an Electrocatalyst Material for Gel Polymer Electrolyte Based Hybrid Zn‐Metal/Air Batteries

Abstract Owing to the exceptional theoretical energy density, capacity, and safety, rechargeable Zn–air batteries (ZABs) have recently gained attention. The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), taking place at the cathode during the discharge and charge of the ZAB device, have sluggish kinetics; thus, the role of efficient electrocatalysts becomes pivotal. In the present work, nanorod‐like structures of cobalt oxide grown over reduced graphene oxide (rGO) have been investigated as an electrocatalyst material for rechargeable ZABs. The Co 3 O 4 /rGO shows a limiting current density of 4.8 mA cm −2 , a high onset potential of 0.85 V at 1600 rpm in ORR, and an evolution potential of 1.8 V at 10 mA cm −2 in OER. The ZAB devices fabricated using the Co 3 O 4 /rGO cathode material display a hybrid cycling mechanism and exhibites a cycle life of 150 h (450 cycles@20 min per cycle) at a current density of 5.2 mA cm −2 , which is significantly higher than that of the bare Co 3 O 4 nano‐cube material. Devices display a specific capacity of 700 mA h . The rGO acts as a substrate for the heterogeneous nucleation of Co 3 O 4 and synergizes the catalytic action by enhancing the conductivity, surface area, and active sites.