Atomic Doping and Anion Reconstructed CoF₂ Electrocatalyst for Oxygen Evolution Reaction

Electrocatalytic water splitting is one of the most promising green solutions for large-scale hydrogen production, which has developed rapidly in recent years. The slow reaction rate of oxygen evolution reaction (OER) has become the bottleneck to improve the electrocatalytic efficiency. Herein, Fe-doped CoF₂ nanowire arrays on 3D nickel foam are prepared by two steps of hydrothermal reaction and fluorination process. The increased catalytic activity sites and accelerated charge transfer rate make the self-supported Fe-doped CoF₂ electrode show excellent OER performance in alkaline electrolyte. An overpotential of 230 mV is only required to release a current density of 10 mA cm⁻². The Tafel slope derived from the polarization curves is 59 mV dec⁻¹, indicating outstanding electrochemical kinetics performance. A stable output current density of 84 mA cm⁻² for more than 96 h is achieved under an invariant overpotential of 338 mV, attributing to the anion reconstruction making part of CoF₂ transform into cobalt hydroxide and further improving its electrocatalytic performance.