Authors: Lingxia Zheng, Weiqing Ye, Yijian Zhao, Zhuoqing Lv, Xiaowei Shi, Qi Wu, Xiaosheng Fang, Huajun Zheng
Published: 2022-12-19
Source: Full article
AbstractThree CoFe‐bimetallic oxides with different compositions (termed as CoFeOx‐A/N/H) are prepared by thermally treating metal‐organic‐framework (MOF) precursors under different atmospheres (air, N2, and NaBH4/N2), respectively. With the aid of vast oxygen vacancies (Ov), cobalt at tetrahedral sites (Co2+(Th)) in spinel Co3O4 is diffused into interstitial octahedral sites (Oh) to form rocksalt CoO and ternary oxide CoFe2O4 has been induced to give the unique defective CoO/CoFe2O4 heterostructure. The resultant CoFeOx‐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 CoFeOx‐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 CoFeOx‐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.