Bifunctional oxygen electrocatalyst based on Fe, Co, and nitrogen co-doped graphene-coated alumina nanofibers for Zn-air battery air electrode

Abstract

Aqueous rechargeable zinc-air battery (RZAB) is an emerging environmentally friendly energy storage device for a wide variety of industrial applications such as electric vehicles, consumer electronics, and stationary power plants. For successful commercialization of RZABs, a cost-effective bifunctional catalyst is highly required to catalyze the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) at the air electrode. Dual transition-metal and nitrogen-doped nanocarbon materials have shown good potential as an affordable and scalable bifunctional oxygen electrocatalysts alternative to Pt-group metal-based catalysts for RZAB. To achieve this goal, we have developed electrocatalysts based on Fe, Co, and nitrogen co-doped graphene-augmented inorganic alumina nanofibers (Fe/Co-NGr). The Fe/Co-NGr catalysts demonstrate high oxygen reduction and evolution reaction reversibility (ΔE) of 0.85–0.88 V due to the graphene-covered nanofibrous structure doped with FeCo alloy nanoparticles and containing nitrogen, transition metal (TM) coordinated to nitrogen and TM oxide active sites. The primary zinc-air battery with Fe/Co-NGr air electrode exhibits a high maximum power density of 149 mW cm−2 and a specific capacity of 807 mAh gZn-1. The RZAB assessment has shown a low charge–discharge voltage gap of 0.86 V and high energy utilization efficiency of 58 % up to 90 h of charge–discharge cycling at 5 mA cm−2.