WSe<sub>2</sub>-VSe<sub>2</sub> Alloyed Nanosheets to Enhance the Catalytic Performance of Hydrogen Evolution Reaction.

Kwon, Ik Seon; Kwak, In Hye; Zewdie, Getasew Mulualem; Lee, Seung Jae; Kim, Ju Yeon; Yoo, Seung Jo; Kim, Jin-Gyu; Park, Jeunghee et al. · ACS Nano · 2022

basic_science · Level V

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Abstract

Tuning the electronic structures of transition metal dichalcogenides (TMD) is essential for their implementation in next-generation energy technologies. In this study, we synthesized composition-tuned WSe<sub>2</sub>-VSe<sub>2</sub> (W<sub>1-<i>x</i></sub>V<sub><i>x</i></sub>Se<sub>2</sub>, <i>x</i> = 0-1) alloyed nanosheets using a colloidal reaction. Alloying the semiconducting WSe<sub>2</sub> with VSe<sub>2</sub> converts the material into a metallic one, followed by a 2H-to-1T phase transition at <i>x</i> = 0.7. Over a wide composition range, WSe<sub>2</sub> and VSe<sub>2</sub> are atomically immiscible and form separate ordered domains. The miscible alloy at <i>x</i> = 0.1 displayed enhanced electrocatalytic activity toward the hydrogen evolution reaction (HER) in an acidic electrolyte. This trend was correlated with the <i>d</i>-band center via a volcano-type relationship. Spin-polarized density functional theory calculations consistently predicted the atomic immiscibility, which became more significant at the 2H-1T phase transition composition. The Gibbs free energy of H adsorption on the basal planes (Se or hole sites) and the activation barriers along the Volmer-Heyrovsky reaction pathway supported the enhanced HER performance of the alloy phase, suggesting that the dispersed V-doped structures were responsible for the best HER catalytic activity. Our study demonstrates how the atomic structure of TMD alloy nanosheets plays a crucial role in enhancing catalytic activity.