In-situ coalesced vacancies on MoSe2 mimicking noble metal: Unprecedented Tafel reaction in hydrogen evolution

Abstract

Transition metal dichalcogenides (TMDs) have shown promising potential as electrocatalyst materials for the hydrogen evolution reaction (HER). However, the low catalytic activity in the basal planes of TMDs results in only limited HER activity, and several strategies to overcome this bottleneck have been proposed, involving various post-synthesis treatments such as introducing chalcogen vacancies or applying mechanical strain. Herein, we demonstrate in-situ modulation of chalcogen vacancy sites during the chemical vapor deposition synthesis of molybdenum diselenides (MoSe2) for application in the HER. We demonstrate for the first time that the Tafel reaction can be activated via in-situ vacancy-engineered MoSe2, resulting in improved onset potential and an exceptionally low Tafel slope, which exhibits one of the lowest values reported for TMDs to date in our knowledge. Density functional theory calculations revealed that vacancy coalescence in the MoSe2 lattice reduced the hydrogen adsorption free energy and diffusion barrier to activate the Tafel reaction. Our approach could contribute to the development of high-performance TMDs-based electrocatalysts with relatively simple processability to make hydrogen production more viable. © 2019 Elsevier Ltd