A nanostructured nickel/carbon matrix as an efficient oxygen evolution reaction electrocatalyst for rechargeable zinc–air batteries

Abstract

An oxygen evolution electrode (OEE) is essential to improve the rechargeablility of Zn–air batteries. Conventional catalyst-loaded OEEs suffer from high cost, complicated manufacturing and poor durability. Here, we present an OEE consisting of nanostructured nickel–carbon (Ni/C) catalysts and a gas diffusion layer (GDL) that demonstrates good electrocatalytic activity and durability in alkaline media. The Ni/C OEE is developed from one-step pyrolysis of a Ni/2-methylimidazole complex grown on GDL carbon paper. The overpotential of the obtained Ni/C is 390 mV at a current density of 10 mA cm⁻². After 2000 cyclic voltammetric cycles from 1.04 V to 1.88 V vs. RHE, the Ni/C OEE retains 75% of its electrocatalytic activity (in terms of the oxygen evolution current at 1.88 V) which is superior to 20 wt% iridium supported on the carbon OEE. Electrochemical and spectroscopic data suggest in situ generated α-Ni(OH)₂/γ-NiOOH and β-Ni(OH)₂/β-NiOOH as the redox couples on the Ni/C OEE. The recurrent rejuvenation of Ni (oxy)hydroxide redox couples and good adhesion of Ni/C catalysts to the matrix are some of the reasons to elucidate high efficiency and good durability of the Ni/C OEE.