Defect‐Induced Atomic Arrangement in CoFe Bimetallic Heterostructures with Boosted Oxygen Evolution Activity
Lingxia Zheng, Weiqing Ye, Zhefei Zhao, Zhuoqing Lv, Xiaowei Shi, Qi Wu, Xiaosheng Fang, Huajun Zheng
Abstract
Abstract Three CoFe‐bimetallic oxides with different compositions (termed as CoFeO x ‐A/N/H) are prepared by thermally treating metal‐organic‐framework (MOF) precursors under different atmospheres (air, N 2, and NaBH 4 /N 2 ), respectively. With the aid of vast oxygen vacancies (O v ), cobalt at tetrahedral sites (Co 2+ (Th)) in spinel Co 3 O 4 is diffused into interstitial octahedral sites (Oh) to form rocksalt CoO and ternary oxide CoFe 2 O 4 has been induced to give the unique defective CoO/CoFe 2 O 4 heterostructure. The resultant CoFeO x ‐H exhibits superb electrocatalytic activity toward water oxidation: overpotential at 10 mA cm −2 is 192 mV, which is 122 mV smaller than that of CoFeO x ‐A. The smaller Tafel slope (42.53 mV dec −1 ) and higher turnover frequency (785.5 h −1 ) suggest fast reaction kinetics. X‐ray absorption spectroscopy, ex situ characterizations, and theoretical calculations reveal that defect engineering effectively tunes the electronic configuration to a more active state, resulting in the greatly decreased binding energy of oxo intermediates, and consequently much lower catalytic overpotential. Moreover, the construction of hetero‐interface in CoFeO x ‐H can provide rich active sites and promote efficient electron transfer. This work may shed light on a comprehensive understanding of the modulation of electron configuration of bimetallic oxides and inspire the smart design of high‐performance electrocatalysts.