Highly active CoP embedded in hollow nitrogen-doped carbon as an efficient bifunctional electrocatalyst for rechargeable zinc-air batteries

Abstract

Aqueous zinc-air batteries provide a possibility to replace fossil fuels. However, developing bi-functional electrocatalysts with high activity, low-cost and environmental friendliness for zinc-air batteries remains a challenge. In this work, we report an efficient bifunctional electrocatalyst (H–CoP@NC) that is fabricated by phosphating a hollow metal organic framework (MOF) prepared using a self-template method. The H–CoP@NC exhibits a half-wave potential of 0.81V (vs. RHE) for the oxygen reduction reaction (ORR), and an overpotential of 390 mV for the oxygen evolution reaction (OER) at a current density of 10 mA cm−2. Remarkably, the H–CoP@NC assembled zinc-air battery possesses a voltage gap of 0.82 V at a current density of 50 mA cm−2, and the voltage gap increases by only 0.01 V after 730 continuous charge and discharge cycles. This excellent electrocatalytic activity for ORR and OER can be attributed to the hollow structure, which improves mass transport during the electrocatalytic reaction, and the synergistic effect between CoP and heteroatom doped carbon skeletons which provide a high density of exposed active sites.