Real-Time Detection of Dynamic Restructuring in KNixFe1-xF3 Perovskite Fluorides for Enhanced Water Oxidation

Abstract

Mechanistic understanding of how electrode–electrolyte interfaces evolve dynamically is crucial for advancing water-electrolysis technology, especially the restructuring of catalyst surface during complex electrocatalytic reactions. However, for perovskite fluorides, the mechanistic exploration for the influence of the dynamic restructuring on their chemical property and catalytic mechanism is unclear due to their poor conductivity that makes the definition of electrocatalyst structure difficult. Herein, for oxygen evolution reaction (OER), various operando characterizations are employed to investigate the structure-activity relationships of the KNi_xFe_1-xF₃@NF. Adding iron to the KNi_xFe_1-xF₃ structure increases metal vacancies, enhancing electrochemical reconstruction. For reconstructed KNi_xFe_1-xF₃ structure, the results from operando Raman, operando X-ray diffraction, operando UV–vis spectroscopy, and differential electrochemical mass spectrometry reveal that the surface Ni sites act as catalytic centers within the amorphous Ni(Fe)OOH active layer, and the incorporation of Fe activates oxidized oxygen ions during water oxidation. Theoretical calculations support this by demonstrating the optimized adsorption-free energy of oxygenated intermediates. Consequently, the KNi_0.5Fe_0.5F₃@NF achieves an overpotential of 281 mV to reach OER current of 150 mA·cm⁻² and maintains stable operation for 200 h. These results highlight a promising pathway to tuning OER mechanisms in perovskite fluorides and offer a new perspective for developing high-efficiency and durable OER catalysts.