Oxygen Evolution Reaction of Amorphous/Crystalline Composites of NiFe(OH)<sub><i>x</i></sub>/NiFe<sub>2</sub>O<sub>4</sub>
Lu Yao, Xiaofeng Wu, Zhibin Geng, Yuan Zhang, Yiqing Fang, Qian Zhu, Na Liang, Minmin Cai, Huazheng Sai, Jianguo Cheng, Songbo Li, Ying Wang, Mei Han, Keke Huang, Shouhua Feng
Abstract
Orbital structures are strongly correlated with catalytic performance, whereas their regulation strategy is still in pursuit. Herein, the Fe 3 d and O 2 p orbital hybridization was optimized by controlling the content of amorphous NiFe(OH) x (a-NiFe(OH) x ), which was grown in situ on crystalline NiFe 2 O 4 (c-NiFe 2 O 4 ) using an ultrasonic reduction method. The results of electron energy loss spectroscopy (EELS) and X-ray absorption spectra (XAS) revealed that the Fe–O a orbital hybridization in a-NiFe(OH) x is effectively strengthened by jointing with the adjacent oxygen (O c ) in c-NiFe 2 O 4, which is further confirmed by the higher antibonding orbital energies based on density functional theory (DFT) calculations. The resultant O a –Fe–O c at the composite interface leads to balanced adsorption and desorption energies. Accordingly, the optimal composite with strong Fe 3 d -O 2 p hybridization results in enhanced OER performance, and the overpotential is 150 mV, lower than that of the pristine sample. This work represents a promising approach to orbital hybridization via the introduction of an amorphous phase to construct highly efficient catalysts.