Activating Inert Basal Planes of MoS₂ for Hydrogen Evolution Reaction through the Formation of Different Intrinsic Defects

Abstract

Nanoscale molybdenum disulfide (MoS 2 ) has attracted ever-growing interest as one of the most promising nonprecious catalysts for hydrogen evolution reaction (HER). However, the active sites of pristine MoS 2 are located at the edges, leaving a large area of basal planes useless. Here, we systematically evaluate the capabilities of 16 kinds of structural defects including point defects (PDs) and grain boundaries (GBs) to activate the basal plane of MoS 2 monolayer. Our first-principle calculations show that six types of defects (i.e., V s , V MoS3 , Mo S2 PDs; 4|8a, S bridge, and Mo−Mo bond GBs) can greatly improve the HER performance of the in-plane domains of MoS 2 . More importantly, V s and Mo S2 PDs and S bridge and 4|8a GBs exhibit outstanding activity in both Heyrovsky and Tafel reactions as well. Moreover, the different HER activities of defects are well-understood by an amendatory band-center model, which is applicable to a broad class of systems with localized defect states. Our study provides a comprehensive picture of the defect-engineered HER activities of a MoS 2 monolayer and opens a new window for optimizing the HER activity of twodimensional dichalcogenides for future hydrogen utilization.

Hydrogen adsorption on MoS2-surfaces: a DFT study on preferential sites and the effect of sulfur and hydrogen coverage

“…Interestingly, for δ S = 5.6 % a reversal of the trend is seen, where in fact ontop adsorption on the monovacancy containing basal plane yields slightly lower ∆G H -values than the corresponding system with divacancies. The observed slightly stronger adsorption to divacant sites compared to monovacancies is in accordance with the findings of Ouyang et al 33 , who report a strengthening of 0.12 eV in the H-adsorption between these configurations.…”

“…Adsorption at the formed hollow sites is observed to be consistently thermoneutral in nature, thus suggesting optimal HER-performance. This finding is further supported by previous studies 18,21,33 .…”

“…The activating effect of inducing S-vacancies in the 2H-MoS 2 basal plane has been studied by Li et al 18 as well as Ouyang et al 33 . We have investigated this further by inducing both singleatom vacancies (V S ) and divacancies (V S 2 ) to a pristine bilayer 2H-MoS 2 basal plane (Mo 72 S 144 ), and employing H-adsorption calculations as a function of θ H .…”

“…Computational studies using density functional theory (DFT) are widely utilized as a complementary method in the experimental search of new potential HER-electrocatalysts 6,13,[25][26][27][28][29][30][31][32][33] . DFT provides means by which to model the electrocatalytically relevant systems at an atomic level and gain detailed insight into the trends and mechanism behind the activity of materials.…”

Defective MoS2 electrocatalyst for highly efficient hydrogen evolution through a simple ball-milling method

“…There are two strategies to optimize the electrochemical performance of MoS 2 including revealing active sites and increasing the electrical conduction for improving the electron transfer [25,26]. Introducing defects has proven to be an effective approach to generate active sites [27]. During the past few years, previous studies confirm that the HER activity of MoS 2 correlates with the number of catalytically active edge sites.…”