Lattice Distortion in High‐Entropy Transition Metal Diselenide for Augmented Hydrogen Evolution

Abstract The high‐entropy strategy offers a viable pathway to activate the inert basal plane of transition metal dichalcogenides (TMDs) for electrocatalysis. This work demonstrates that the “lattice distortion effect”, one of the core effects of high‐entropy materials, plays a crucial role in activating the basal plane of TMDs. A high‐entropy diselenide (ReNbTaMoW)Se 2 (denoted as HESe 2 ) is synthesized via solid‐state reaction. Single‐crystal X‐ray diffraction and atomic resolution scanning transmission electron microscopy reveal a unique fivefold‐modulated structure in HESe 2 , which unexpectedly distorts the rigid trigonal prismatic motif. HESe 2 exhibits exceptional activity for hydrogen evolution reaction (HER), showing a low overpotential of 31 mV at a current density of 10 mA cm −2 , comparable to state‐of‐the‐art precious metal catalysts. In situ X‐ray photoelectron spectroscopy indicates that the distorted structure of HESe 2 remains stable during the HER process. A proton exchange membrane (PEM) electrolyser assembled with HESe 2 cathodic catalyst shows competitive performance and durability with negligible degradation over 400 h. Density functional theory calculations reveal the electron accumulation regions induced by lattice distortion as high‐activity sites, thereby driving the augmented HER performance of HESe 2 . This work presents a universal strategy for boosting the basal plane activity of layered materials through unique lattice distortion effect.