WSe₂–VSe₂ Alloyed Nanosheets\nto Enhance the Catalytic Performance of Hydrogen Evolution Reaction

Abstract

Tuning the electronic structures of transition metal\ndichalcogenides\n(TMD) is essential for their implementation in next-generation energy\ntechnologies. In this study, we synthesized composition-tuned WSe₂–VSe₂ (W_1–<i>x</i>V_<i>x</i>Se₂, <i>x</i> = 0–1) alloyed nanosheets using a colloidal reaction. Alloying\nthe semiconducting WSe₂ with VSe₂ converts the\nmaterial into a metallic one, followed by a 2H-to-1T phase transition\nat <i>x</i> = 0.7. Over a wide composition range, WSe₂ and VSe₂ are atomically immiscible and form separate\nordered domains. The miscible alloy at <i>x</i> = 0.1 displayed\nenhanced electrocatalytic activity toward the hydrogen evolution reaction\n(HER) in an acidic electrolyte. This trend was correlated with the <i>d</i>-band center via a volcano-type relationship. Spin-polarized\ndensity functional theory calculations consistently predicted the\natomic immiscibility, which became more significant at the 2H-1T phase\ntransition composition. The Gibbs free energy of H adsorption on the\nbasal planes (Se or hole sites) and the activation barriers along\nthe Volmer–Heyrovsky reaction pathway supported the enhanced\nHER performance of the alloy phase, suggesting that the dispersed\nV-doped structures were responsible for the best HER catalytic activity.\nOur study demonstrates how the atomic structure of TMD alloy nanosheets\nplays a crucial role in enhancing catalytic activity.