Abstract
In this paper, the effects of the sulfur vacancy (VS) distribution in 2H–MoS2 monolayer on the H2 evolution mechanism and activity are researched by density functional theory (DFT) calculations. The calculation results reveal that the H2 generation on VS follows the Volmer-Heyrovsky mechanism with the Heyrovsky reaction as the rate determined step (RDS) with an energy barrier of 18.5 kcal/mol. When two VS are separated by one S atom, the H2 evolution on VS remains the Heyrovsky-step-determined Volmer-Heyrovsky mechanism and the RDS energy barrier increases to 20.0 kcal/mol. Removing adjacent S of VS causes that the Tafel-step-determined Volmer-Tafel mechanism works for HER and the barrier of RDS increases to 21.4 kcal/mol. Though the barriers of RDS ascend when the concentration of VS is enhanced by these two strategies, the Tafel step can take place at a lower potential and more VS are exposed. Therefore, two adjacent or next-near VS may obtain better H2 generation performance. Three adjacent or spaced out VS by one S may be less favorable for HER.
Published Version
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