Ionic liquid-assisted synthesis of cobalt-iron difluoride electrocatalysts for oxygen evolution reaction

Surface reconstruction is a promising approach to obtain highly efficient electrocatalysts for oxygen evolution reaction (OER), which is vital for many renewable energy conversion and storage processes. Herein, we synthesized Co-Fe based difluoride by a simple solvothermal treatment process with the assistance of an ionic liquid ([Bmim]BF4). The final sample originated from Co0.67Fe0.33F2 demonstrated the highest electrocatalytic activity, generating a current density of 10 mA/cm(2) at an overpotential of 270 mV. The appropriate amount of iron dopant can increase the number of active sites. Besides, the in-situ leaching of fluorine accompanied with OER was found to generate metal oxyhydroxide layer with abundant oxygen vacancies, thus leading to the high performance of the electrocatalysts.