FeCoNiCuIr High-Entropy Alloy Catalysts for Hydrogen Evolution Reactions with Improved Desorption Behavior by Tuning Antibonding Orbital Filling

Proton-exchange membrane water electrolysis (PEMWE) demands highly efficient and stable electrocatalysts for the hydrogen evolution reaction (HER). Noble metals, such as Ir and Pt, are widely employed as HER catalysts as a result of high corrosion resistance and high HER activity under a strong acidic environment. However, as a result of the scarcity and high cost of noble metals, researchers are focusing on developing catalysts with a reduced content of noble metals while enhancing a high catalytic activity per unit mass. Herein, FeCoNiCuIr catalysts were designed using a high-entropy platform to enhance the intrinsic and mass activity. Incorporation of a transition metal (TM) modifies the electronic structure of Ir as a result of charge transfer from the TM to Ir, which optimizes the hydrogen binding energy. FeCoNiCuIr with optimized hydrogen binding energy required a low overpotential of 71 mV at a current density of −10 mA cm–2. The high mass activity of 3.69 A mgIr–1 was exhibited in FeCoNiCuIr at the overpotential of 50 mV, which is 92.2% higher than that of the Ir mono-element (1.92 A mgIr–1). FeCoNiCuIr showed stable performance during chronopotentiometry performed at a constant current density of −100 mA cm–2 for 48 h, demonstrating the excellent durability of the high-entropy alloy (HEA). This study presents the design principle of HEA catalysts capable of improving both activity and durability simultaneously.