A multisite HEA catalyst with etching-induced active surface for synergistic alkaline hydrogen evolution

Developing high-activity electrocatalysts is crucial for the sustainable hydrogen production. This study presents a scalable strategy that combines arc-melted high-entropy alloy (HEA) synthesis with selective acid etching to create a superior catalyst for alkaline hydrogen evolution reaction (HER). The designed Nb 30 Mo 25 V 20 Pt 15 Ir 10 HEA undergoes controlled etching, which selectively removes specific elements to construct a highly active surface with exposing and stabilizing Pt/Ir active sites. The optimized catalyst demonstrates exceptional performance, achieving an ultralow overpotential of 24 mV at 10 mA cm −2 , a Tafel slope of 35.6 mV dec −1 , and remarkable stability in 1.0 M KOH electrolyte. More importantly, it exhibits a superior precious metal mass activity of 0.081 A mg −1 Pt + Ir and a high turnover frequency of 1.14 s −1  at 100 mV, surpassing the commercial Pt/C. Experimental characterization and DFT calculations reveal a synergistic multisite mechanism where Pt sites facilitate optimal H∗ adsorption while Mo–Ir bridge sites modulate surface OH∗ interaction, collectively enhancing the reaction kinetics. This work provides new insights into designing high-performance, cost-effective electrocatalysts through rational HEA engineering and post-synthetic surface modification.