Tunable hydrogen evolution reaction of vacancy-defective MoSe2/WSe2 heterojunctions based on first-principle calculation

Abstract

Two-dimensional transition metal disulfides (TMDs) heterojunction is a very promising non-precious metal catalyst that has been widely used as a catalyst for hydrogen evolution reactions. In this paper, the effects of different positions of Se vacancies on the electronic structure and hydrogen evolution reaction electrocatalyst of MoSe2/WSe2 heterojunction are investigated by first-principles calculations. After the introduction of vacancy, defect states appear between the conduction band bottom and the Fermi energy level of the heterojunction. This is more favorable for the electron transfer between H and the substrate. The results of the density of states calculations indicate that the defect states appear because the d orbitals of the transition metal atoms containing the Se vacancy layer hybridize with the p orbitals of the Se atoms. The differential charge density indicates that the Se vacancies promote the charge transfer of MoSe2/WSe2. In addition, calculations of the Gibbs free energy for the hydrogen evolution reaction of heterojunctions show that Se vacancies (especially the outer vacancies) enhance the electrocatalytic hydrogen precipitation performance of heterojunctions. The results provide a new way to regulate the hydrogen evolution properties of MoSe2/WSe2 heterojunctions.