Cobalt nitride embedded holey N-doped graphene as advanced bifunctional electrocatalysts for Zn-Air batteries and overall water splitting

Exploration of cost-effective and highly durable carbon-based multifunctional electrocatalysts for energy conversion and storage devices (e.g., metal-air batteries) is of critical significance. Herein, we present a unique worm-like structure of hierarchically porous nitrogen-doped graphene (N-rGO) embedded with cobalt nitride (Co5.47N) nanoparticles (named as Co5.47N@N-rGO) by tannic acid assisted nitridation method for Zn-air batteries and overall water splitting. Benefiting from the unique worm-like structure to expose more active sites and the synergy advantages of a close contact between Co5.47N nanoparticles and the N-rGO sheets, the Co5.47N@N-rGO exhibits efficient bifunctional catalytic activities toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Notably, Zn-air batteries assembled with Co5.47N@N-rGO-750 show a power density of 120.7 mWcm(-2) and excellent cycling stabilities for 330 h in an aqueous electrolyte. More interestingly, when assembled into a flexible solid-state rechargeable Zn-air battery, the Co5.47N@N-rGO-750 displays a specific capacity of 610 mAh g(zn)(-1) and good cycling stability over 40 h. Moreover, the integrated device for water splitting powered by Zn-air batteries is also fabricated by using the Co5.47N@N-rGO-750 electrocatalyst, exhibiting a good gas generation rate. This work offers a new strategy to design and synthesize efficient multifunctional carbon-based electrocatalysts applied in electrochemical devices. (C) 2019 Elsevier Ltd. All rights reserved.