N-doped-graphene-supported Ni/Co bimetallic catalysts for zinc-air batteries

Abstract

Electrocatalysis is essential for enhancing the energy conversion efficiency of zinc–air batteries. Nonetheless, the high cost and insufficient stability of electrocatalysts continue to hinder their commercial application. This study introduces a bifunctional composite electrocatalyst, NiCo–NG, consisting of Ni/Co bimetallic nanoparticles. The in situ integration of nanoscale graphene mitigates the agglomeration of Ni/Co metal atoms, resulting in a porous structure with a high specific surface area up to 244.6 m² g⁻¹. Notably, the NiCo–NG catalyst demonstrates enhanced conductivity, achieving an oxygen reduction reaction (ORR) half-wave potential of 0.793 V and a limiting current density of 7.64 mA cm⁻². This catalyst exhibits superior performance to commercial Pt/C electrodes, which exhibit a half-wave potential of 0.836 V and a limiting current density of 0.6 mA cm⁻². Moreover, the overpotential for the oxygen evolution reaction (OER) at a current density of 10 mA cm⁻² is only 306.3 mV. The introduction of Ni significantly augments the catalytic activity. Employing this dual-functional catalyst in rechargeable zinc–air batteries yields a maximum power density of 181.9 mW cm⁻² and a specific capacity of 804.2 mAh·g_Zn⁻¹. In addition, the fabricated battery demonstrates remarkable stability, enduring up to 3000 charge–discharge cycles. Ultimately, this research offers a novel electrocatalyst that could advance the commercialization of zinc–air batteries.