Polytypic Phase Transition of Nb<sub>1–<i>x</i></sub>V<sub><i>x</i></sub>Se<sub>2</sub> via Colloidal Synthesis and Their Catalytic Activity toward Hydrogen Evolution Reaction
In Hye Kwak, Ik Seon Kwon, Getasew Mulualem Zewdie, Tekalign Terfa Debela, Seungjae Lee, Ju Yeon Kim, Seung Jo Yoo, Jin-Gyu Kim, Jeunghee Park, Hong Seok Kang
Abstract
Polytypes of two-dimensional transition metal dichalcogenide can extend the architecture and application of nanostructures. Herein, Nb 1– x V x Se 2 alloy nanosheets in the full composition range ( x ) were synthesized by a colloidal reaction. At x = 0.1–0.3, a phase transition occurred from various hexagonal (three 2H and one 4H types) phase NbSe 2 to an atomically homogeneous 1T phase VSe 2 . Density functional theory calculations also revealed a polytypic phase transition at x = 0.3, which was shifted close to 0 in the presence of Se vacancies. Furthermore, the calculations validate favorable formation of Se vacancies at the phase transition. The sample at x = 0.3 exhibited enhanced electrocatalytic activity toward the hydrogen evolution reaction (HER) in 0.5 M H 2 SO 4 . The Gibbs free energy indicates that the catalytic HER performance is correlated with the active Se vacancy sites of polytypic structures.