Rapid and in-depth reconstruction of fluorine-doped bimetallic oxide in electrocatalytic oxygen evolution processes.

Abstract

Most transition metal-based electrocatalysts, when used for the oxygen evolution reaction (OER), undergo significant restructuring under alkaline conditions, forming localized oxides/hydroxides (MOOH), which act as the real active centers, activating adjacent metal sites and creating new active sites that enhance electrocatalytic behavior. Nevertheless, inducing rapid and in-depth self-reconstruction of catalyst surfaces remains a huge challenge. Herein, this work achieves rapid and in-depth self-reconstruction by doping fluorine into the lattice of transition metal oxides (MO). As surface restructuring progresses, the continuous leaching of F^- ions by the alkaline electrolyte generates OH^- ions rapidly, which facilitates the transformation from MO to M-OOH active species, thereby exposing additional active sites. Meanwhile, F doping shifts the d-band center closer to the Fermi level while increasing the occupancy of Ni and Co d-orbitals, leading to a redistribution of electronic density and enhanced spin polarization. Additionally, the significant increase in the energy levels of the e_g and t_2g orbitals strengthens d-d orbital coupling, optimizing the adsorption energy of oxygen-containing species and facilitating catalyst surface reconstruction. Accordingly, the catalysts require a remarkably low overpotential of 247 mV to achieve a current density of 10 mA cm^-2. Overall, this work provides a valuable approach for constructing pre-catalysts capable of rapid and in-depth self-reconstruction during the OER process.