Controlled three-dimensional leaf-like NiCoO2@NiCo layered double hydroxide heterostructures for oxygen evolution electrocatalysts in rechargeable Zn–air batteries

Abstract

Rechargeable zinc-air batteries (ZABs) have garnered attention as a viable choice for large-scale energy storage due to their advantageous characteristics, such as high energy density and cost-effectiveness. Strategies aimed at improving the kinetics of the oxygen evolution reaction (OER) through advanced electrocatalytic materials or structural designs can significantly enhance the efficiency and longevity of ZABs. In this study, we introduce a three-dimensional (3D) leaf-vein system heterojunction architecture. In this structure, NiCoO2 nanowire arrays form the central vein, surrounded by an outer leaf composed of NiCo layered double hydroxide (LDH) nanosheets. All these components are integrated onto a substrate made of Ni foam. Notably, when tested in an alkaline environment, the NiCoO2@NiCo LDH exhibited an overpotential of 272 mV at a current density of 10 mA cm−2, and extended durability evaluations over 12 h underscored its robustness at 99.76 %. The rechargeable ZABs achieved a peak power density of 149 mW cm−2. Furthermore, the NiCoO2@NiCo LDH demonstrated stability by maintaining high round-trip efficiencies throughout more than 680 cycles (equivalent to 340 h) under galvanostatic charge–discharge cycling at 5 mA cm−2. The leaf-vein system heterojunction significantly increased the active sites of the catalysts, facilitating charge transport, improving electronic conductivity, and enhancing overall stability.