ZIF‐derived N‐doped carbon nanorods supporting bimetallic CoFe single‐atoms/nanoclusters as bifunctional oxygen electrocatalysts for stable Zn‐air batteries
Hong‐Shuang Fan, Fei‐Xiang Ma, Zi-Hao Liu, Wenhui Wang, Zheng‐Qi Liu, Xiongyi Liang, Yue Du, Yang Yang Li, Liang Zhen, Cheng‐Yan Xu
Abstract
Abstract High‐performance bifunctional oxygen electrocatalysts that simultaneously boost the sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) need to be developed for advanced rechargeable Zn‐air battery applications. In this work, a zeolitic imidazolate framework (ZIF)‐phase conversion associated with a subsequent thermal fixing strategy was developed to fabricate bimetallic CoFe single atoms/clusters embedded in N‐doped carbon (denoted as CoFe–N–C) nanorods, which can serve as efficient bifunctional ORR/OER electrocatalysts. Microstructural observation and X‐ray absorption spectroscopy analysis confirm the co‐existence of highly active Co/Fe–N x dual sites and CoFe alloy nanoclusters. X‐ray photoelectron spectroscopy (XPS) results prove that implanting secondary Fe atoms into Co–N–C matrix nanorods can induce electronic redistribution of atomic Co/Fe active sites and generate synergistic effects, which would optimize the adsorption energy of the reaction intermediates and thus enhance the bifunctional ORR/OER activity. The bimetallic CoFe–N–C nanorods exhibit significantly enhanced bifunctional ORR/OER activity and stability than the monometallic Co/Fe–N–C nanorods in alkaline electrolytes in terms of a very positive half‐wave potential of 0.90 V (vs. reversible hydrogen electrode (RHE)) for ORR, and an overpotential of 440 mV to reach current density of 10 mA·cm −2 for OER, yielding a small overpotential gap of 0.77 V. Furthermore, the rechargeable Zn‐air batteries using bimetallic CoFe–N–C nanorods as air–cathode catalyst demonstrates peak power density of 200.7 mW·cm −2 and robust cycling stability of up to 200 h, corresponding to 1200 discharge–charge cycles.