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

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.