Dual‐Site Synergistic Ultrathin Pt‐Based High‐Entropy Alloy Nanosheets Enabling High‐Performance Industrial Alkaline HER

ABSTRACT Two‐dimensional (2D) Pt‐based high‐entropy alloys (HEAs) are promising electrocatalysts due to fully exposed active surfaces and tunable multi‐element synergy. However, synthesizing such ultrathin, homogeneous nanostructures remains a formidable challenge, as conventional methods struggle to overcome the intrinsic anisotropic growth tendencies of Pt‐based systems. Herein, we develop a nucleation‐controlled strategy using Pd as structural template to achieve ultrathin PtPdRuNiInSn HEA nanosheets with atomic homogeneity. This structure combines maximized surface accessibility with multi‐element synergy, delivering exceptional alkaline hydrogen evolution activity of 16.5 A mg −1 at −70 mV versus RHE, a 19.6‐fold enhancement over Pt/C. Operando spectroscopy and DFT calculations reveal that Pt/Pd/Ru sites optimize H* adsorption while Ni/In/Sn sites facilitate OH* activation, synergistically lowering the reaction barriers. The entropy‐stabilized configuration demonstrates outstanding durability (negligible activity loss after 50000 cycles) and industrial viability, enabling anion‐exchange membrane electrolyzers to operate steadily for 2500 hours at 1 A cm −2 . This work establishes a general paradigm for designing advanced Pt‐based 2D high‐entropy electrocatalysts.