Tuning the Electronic Structure of Ni<sub>2</sub>P through Fe Doping to Trigger the Lattice-Oxygen-Mediated Oxygen Evolution Reaction
Minglei Yan, Wengang Liu, Kun Xiang, Yanmei Li, Youwen Zhang, Jun‐Jie Zhang, Yuxiao Ren, Yisong Sun, Yan Li, Jian Liu, Junheng Fu, Zhiwei Lu, Yang Zhao
Abstract
Developing cost-effective electrocatalysts for efficient seawater splitting requires a fundamental understanding of the oxygen evolution reaction (OER) mechanism. Herein, iron-doped nickel phosphide (Fe–Ni 2 P) is synthesized via a hydrothermal–impregnation–phosphidation strategy to investigate the role of Fe incorporation in modulating the electronic structure and OER pathways. Mechanistic investigations demonstrate that Fe doping triggers a shift from adsorbate evolution mechanism (AEM) to lattice oxygen-mediated (LOM) pathways, evidenced by pH-dependent kinetics, tetramethylammonium cation probing, and in situ electrochemical impedance spectroscopy (EIS). The LOM mechanism involves nonconcerted proton–electron transfers, facilitated by accelerated hydroxide adsorption ( k s = 0.275 s –1 ) and dynamic surface reconstruction into amorphous NiOOH. The reduced activation energy (27.1 kJ mol –1 ) and lower charge-transfer resistance in Fe–Ni 2 P underscore its superior thermodynamics and kinetics. X-ray photoelectron spectroscopy and EIS further validate lattice oxygen activation and oxygen vacancy accumulation during the OER process. Electrochemical studies reveal that Fe–Ni 2 P exhibits a low overpotential of 220 mV at 10 mA cm –2 and remarkable stability through phosphate-mediated Cl – repulsion and dynamic surface reconstruction involving lattice oxygen activation in alkaline seawater. This work establishes Fe-induced electronic modulation as a critical strategy for activating LOM-dominated catalysis in transition metal phosphides.