Bifunctional oxygen electrocatalysts with WN@Ni nanostructures implanted on N-doped carbon nanorods for rechargeable Zn-Air batteries

Abstract

Achieving the rational design of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) bifunctional noble metal-free electrocatalysts has become one of the key research areas for the application of rechargeable Zn-air batteries (ZABs), which still remains a significant challenge. Herein, an in-situ polyaniline nitriding strategy has been developed to fabricate WN-Ni heterostructured catalysts. Polyaniline serves as both the carbon source and the N species that can in situ release gas (NH3) to produce the WN phase. As-fabricated WN-Ni heterostructured catalyst exhibits excellent activity towards ORR and OER, in which the half-wave potential is 0.76 V for ORR, and the over-potential for OER is 1.68 V at 10 mA cm−2. Due to its exceptional ORR/OER activities, the assembled rechargeable ZAB obtains a high power density of 165 mW cm−2. It also exhibits outstanding stability after being subjected to a discharge-charge cycle procedure (>400 h). The remarkable activity of the WN-Ni heterostructured materials should be attributed to their hierarchical nanorod-nanoparticle structure, proper crystallinity of WN-Ni, and good charge/mass transfer ability, which effectively regulate the electron redistribution at the WN-Ni heterointerface and facilitate the charge transfer between two entities.