Wafer‐Scale 2D High‐Entropy Transition Metal Dichalcogenide Thin‐Film Catalysts for Efficient and Durable Photoelectrochemical Hydrogen Production

ABSTRACT Photoelectrochemical (PEC) performance of conventional 2D transition metal dichalcogenides (TMDs) in hydrogen evolution reaction (HER) is constrained by the limited selection of metal cations, predominantly MoS 2 , whose inert basal planes and unstable 1T phases hinder PEC efficiency. High‐entropy TMDs, in which local lattice distortion and charge redistribution occur within a van der Waals layered structure, are expected to overcome these intrinsic limitations by improving catalytic activity, photocarrier dynamics, and phase stability. Here, we demonstrate a wafer‐scale 2D high‐entropy (MoWTaNbRu)S 2 thin‐film catalyst with distorted 1T phase on p ‐Si photocathode for PEC‐HER. The high‐entropy effect induces substantial electronic redistribution, enhancing the contribution of d ‐orbitals near the Fermi level and optimizing hydrogen adsorption energetics. PEC kinetic analyses, including intensity‐modulated photocurrent spectroscopy, demonstrate that (MoWTaNbRu)S 2 markedly suppresses the recombination of photogenerated charge carriers, enabling more efficient charge extraction and accelerated interfacial reaction kinetics. Furthermore, the high‐entropy‐driven stabilization of the metastable 1T phase ensures excellent durability of the photocathode. As a result, the (MoWTaNbRu)S 2 /TiO 2 / p ‐Si photocathode shows a remarkable photocurrent density and stability for over 100 h, outperforming single‐metal TMDs. This study demonstrates how configurational entropy enhances catalytic activity, photocarrier transport, and phase stability of TMDs, establishing a general design principle for next‐generation PEC catalysts.