Site-Differentiated High-Entropy Alloy Surface Enables Efficient Hydrogen Evolution in Acidic and Alkaline Media

Abstract Efficient hydrogen evolution reaction (HER) in acidic and alkaline media requires distinct catalytic functions, including H2O activation, *H adsorption/desorption and *OH regulation, which are difficult to integrate within a single catalytic surface. Herein, PtNiRuFeW high-entropy alloy nanoparticles anchored on carbon nanofibers (PtNiRuFeW/CNFs) are constructed through electrospinning-assisted carbothermal reduction to create a continuous site-differentiated multicomponent surface. The high-entropy configuration induces a broad d-state distribution and pronounced electronic reconstruction, generating element-dependent adsorption environments for HER intermediates. In situ spectroscopy and density functional theory calculations reveal that Fe/Ni-associated sites promote H2O activation and *OH stabilization during alkaline HER, with Fe sites exhibiting a low H2O dissociation barrier of 0.08 eV. Ru-associated sites preferentially accommodate H* intermediates, while electronically reconstructed Pt sites optimize the H* adsorption/desorption balance under acidic conditions, giving a low H* desorption barrier of 0.22 eV. The PtNiRuFeW/CNFs requires only 45 and 90 mV to reach 100 mA cm–2 in 1.0 M KOH and 0.5 M H2SO4, respectively. Moreover, an anion-exchange-membrane water electrolyzer using PtNiRuFeW/CNFs as the cathode maintains stable operation at 500 mA cm–2 for 470 h. This work establishes site-differentiated high-entropy catalysis as a strategy for coupling acidic and alkaline HER elementary steps within one continuous alloy surface.