One-step integration of Co Ni phosphides in N, P co-doped carbons towards highly efficient oxygen electrocatalysis for rechargeable Zn-air battery

Abstract

Abstract The development of highly efficient and robust bifunctional oxygen electrocatalysts is of great importance for optimizing the performance of rechargeable Zn-air batteries. In this study, Co-Ni phosphides encapsulated in N, P co-doped carbon (CoNiP/PNC) were prepared by a simple one-step pyrolysis method. The obtained catalyst exhibited outstanding oxygen reduction and oxygen evolution reaction (ORR and OER) activities in alkaline media. It exhibited a positive half-wave potential of 0.84 V versus the reversible hydrogen electrode for ORR, as well as a low overpotential of 470 mV to achieve 10 mA cm-2 for OER, comparable with the benchmark Pt/C and IrO2 catalysts. Furthermore, the rechargeable Zn-air battery was fabricated, which showed a high specific capacity of 729.3 mAh gZn-1, a high peak power density of 171.0 mW cm-2, and good stability. It reveals that the interplay between heteroatom-doped carbon layers and Co-Ni phase leads to the high ORR activity, and the in-situ formed bimetallic hydroxides/oxides contribute to the great OER performance. This work would inspire the future development of bifunctional electrocatalysts towards electrocatalysis in energy conversion and storage fields.