Interfacial water reconstruction in high-entropy alloys breaks thermodynamic scaling relations for hydrogen evolution.

Abstract

The alkaline hydrogen evolution reaction (HER) is governed by the kinetic incompatibility between water dissociation and hydrogen adsorption. The conventional Pt-based catalysts are further limited by thermodynamic scaling relations that hinder the concurrent optimization of the Volmer and Tafel steps. Herein, we report a hexanary PtFeNiCoMoPd@rGO (reduced graphene oxide, rGO) high-entropy alloy (HEA) that introduces a localized electronic polarization field to regulate the interfacial water microenvironment. Density functional theory (DFT) calculations show that multimetallic integration upshifts the Pt d-band center and yields a near-thermoneutral hydrogen adsorption free energy (ΔGH⁎ = -0.080 eV). Mechanistically, Ni and Mo sites promote water dissociation, while Fe, Co, and Pd tune the electronic structure of Pt domains to balance H* adsorption and H2 desorption. The optimized PtFeNiCoMoPd@rGO-500 catalyst delivers 10 mA cm-2 at an overpotential of 13 ± 1.7 (n = 3) mV with a Tafel slope of 15 ± 2.0 (n = 3) mV dec-1, outperforming commercial Pt/C (35 mV and 38 mV dec-1, respectively). In addition, it exhibits a mass activity of 2.7 A mg-1 and stable operation for over 100 h. In situ Raman spectroscopy further reveals that the catalyst induces a transition of interfacial water from a disordered state to an active four-fold hydrogen-bonded network. These results highlight atomic-level polarization engineering as an effective strategy to break the scaling limitations of alkaline HER.