Oxygen Evolution Reaction of Amorphous/Crystalline Composites of NiFe(OH)<sub><i>x</i></sub>/NiFe<sub>2</sub>O<sub>4</sub>.

Yao, Lu; Wu, Xiaofeng; Geng, Zhibin; Zhang, Yuan; Fang, Yiqing; Zhu, Qian; Liang, Na; Cai, Minmin et al. · ACS Nano · 2025

basic_science · Level V

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Abstract

Orbital structures are strongly correlated with catalytic performance, whereas their regulation strategy is still in pursuit. Herein, the Fe 3<i>d</i> and O 2<i>p</i> orbital hybridization was optimized by controlling the content of amorphous NiFe(OH)<sub><i>x</i></sub> (a-NiFe(OH)<sub><i>x</i></sub>), which was grown in situ on crystalline NiFe<sub>2</sub>O<sub>4</sub> (c-NiFe<sub>2</sub>O<sub>4</sub>) using an ultrasonic reduction method. The results of electron energy loss spectroscopy (EELS) and X-ray absorption spectra (XAS) revealed that the Fe-O<sub>a</sub> orbital hybridization in a-NiFe(OH)<sub><i>x</i></sub> is effectively strengthened by jointing with the adjacent oxygen (O<sub>c</sub>) in c-NiFe<sub>2</sub>O<sub>4</sub>, which is further confirmed by the higher antibonding orbital energies based on density functional theory (DFT) calculations. The resultant O<sub>a</sub>-Fe-O<sub>c</sub> at the composite interface leads to balanced adsorption and desorption energies. Accordingly, the optimal composite with strong Fe 3<i>d</i>-O 2<i>p</i> 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.