Activating Octahedral Center in Co‐Doped NiFe<sub>2</sub>O<sub>4</sub> via Bridging Amorphous MoS<i><sub>x</sub></i> for Electrocatalytic Water Oxidation: A Case for <i>e<sub>g</sub></i> Orbital Regulation in Spinel Oxide
Lu Yao, Xiaofeng Wu, Beining Zheng, Jinghai Liu, Zhibin Geng, Yuan Zhang, Minmin Cai, Zhiyu Shao, Mengpei Jiang, Yaowen Zhang, Yu Chen, Keke Huang, Shouhua Feng
Abstract
Abstract Moderate e g filling for octahedral metal cations (M Oh ) is strongly correlated with the electrocatalytic water oxidation performance in the oxides system. Here, the e g fillings of Ni Oh and Fe Oh in NiFe 2 O 4 ‐based spinel are controllably regulated by introducing an external radical of catalytically inactive MoS x as an electron acceptor via a novel ultrasonic anchored pyrolysis strategy. The electron occupied in e g orbit of M Oh emigrates with the amount of MoS hanging on the apical of octahedral sites, and results in a salutary transition from high to medium e g occupancy state, as confirmed by the X‐ray absorption spectroscopy and X‐ray photoelectron spectroscopy. In addition, benefiting from the abundant unsaturated S atoms in amorphous MoS x , the M Oh at the surface furthest activates and consequently shows a superior water oxidation performance. Density functional theory also reveals that the e g fillings of Ni and Fe decrease to 1.4 and 1.2 after MoS x modification, which can effectively reduce the free energy of the OOH* intermediates in the oxygen evolution reaction process. This work opens an avenue for further releasing the electrocatalytic activity of octahedral sites through bridging external phases with rational electron‐capturing/donating capability.