Hierarchical cobalt-nitrogen-doped carbon composite as efficiently bifunctional oxygen electrocatalyst for rechargeable Zn-air batteries

Abstract

Developing cost-effective bifunctional oxygen electrocatalysts with superior catalytic performance is essential for the large-scale application of rechargeable Zn-air batteries. Herein, a cobalt-nitrogen-doped carbon catalyst Co-UA-OCB with heavy nitrogen content has been synthesized. The N-doped graphene sheets from carbonized uric acid wrapped on the particles of carbon black to construct a hierarchical microstructure. Benefiting from the higher electrochemical active surface area and well dispersed cobalt particles, the catalyst exhibits a remarkable bifunctional activity toward oxygen reduction (ORR) and evolution reactions (OER) with 0.834 V of half-wave potential for ORR and 1.621 V of OER potential at 10 mA cm2. The rechargeable Zn-air battery fabricated with Co-UA-OCB as the air electrode, delivers 142 mW cm−2 of maximum power density, 799 mAh g−1 of specific capacity, 1000 mWh g−1 of energy density and 1.24–1.29 V of running voltage at 10 mA cm2 of current density. The battery exhibits excellent durability and rechargeability, indicating the Co-UA-OCB is a promising candidate to replace the precious metal-based electrocatalyst for rechargeable Zn-air batteries.