Reconfiguration and activation induced by characteristic migration of transition metal ions between interfaces of high-entropy oxygen evolution catalysts†

Abstract

The tremendous potential of high-entropy alloys (HEA) in the electrocatalysis of the oxygen evolution reaction (OER) is well known, but many issues pertaining to building more reliable HEA systems to maximize its synergistic advantages and explaining their complex electrochemical interface behavior need to be discussed. Herein, a convenient composite metal–organic framework (MOF) co-pyrolysis method is designed to reconstruct the precursor in a high-temperature inert atmosphere and prepare a core–shell structure nitrogen-containing carbon nanotube-coated six-metal alloy (FeCoNiVCrZn HEA) as an excellent alkaline medium OER catalyst. It can achieve a working current density of 10 mA cm⁻² at 249 mV overpotential, and the current fluctuation range is less than 3.12% after constant voltage operation for an extended time in 1 M KOH electrolyte. Its electrocatalytic activity and stability surpass those of the same type of alloy catalyst and commercial IrO₂/C catalyst. We tracked the trend of the concentration and chemical state of metal ions between two phases during the electrochemical process and found that the interface reconfiguration of the high-entropy alloy is regulated by the characteristic transition metal migration behavior. On this basis, through density functional theory (DFT) calculation, we further explored the alkaline medium surface metal dissolution and surface reconfiguration behavior and verified that the active MOOH (M = Fe, Co and Ni) phase plays a key role in the reaction steps for the adsorption of the oxygen species. This work provides a unique perspective for the study of HEA in OER structure optimization and interface behavior and shows a new prospect for the development of advanced OER electrocatalysts.