Unlocking the Dynamic Reconstruction of Electrocatalysts: The Triggering Role of Fluoride in Enhancing OER Kinetics

The dynamic reconstruction of electrocatalyst surfaces into active phases plays a crucial role in enhancing the oxygen evolution reaction (OER), yet the mechanistic role of anion adsorption in driving this transformation remains poorly understood. In this study, we reveal that fluoride serve as a powerful trigger for rapid surface reconstruction by significantly enhancing the adsorption of hydroxyl species (OH^-), leading to the formation of a highly defective and metastable Fe-doped CoOOH active phase. Through a combination of in situ Raman spectroscopy, XPS, and electrochemical analysis, we directly observe the reconstruction pathway and demonstrate improved adsorption kinetics induced by fluoride. In situ ATR-FTIR and differential electrochemical mass spectrometry confirm that the reconstructed surface optimizes the binding of oxygenated intermediates and operates via an adsorbate evolution mechanism. Density functional theory calculations provide atomic-level insights, showing that fluoride modification shifts the d-band center toward the Fermi level, strengthening intermediate adsorption and significantly lowering the energy barrier of the rate-determining step. The resulting electrocatalyst exhibits exceptional OER performance, achieving a low overpotential of 254 mV at 10 mA/cm² and outstanding long-term stability over 120 h at a high current density of 375 mA/cm² in an alkaline electrolyte, highlighting its potential for practical water-splitting applications.