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

Abstract

We report a comprehensive computational study of the intricate structure-property relationships governing the hydrogen adsorption trends on MoS 2 edges with varying S-and H-coverages, as well as provide insights into the role of individual adsorption sites. Additionally, the effect of singleand dual S-vacancies in the basal plane on the adsorption energetics is assessed, likewise with an emphasis on the H-coverage dependency. The employed edge/site-selective approach reveals significant variations in the adsorption free energies, ranging between ∼ ±1.0 eV for the different edges-types and S-saturations, including differences of even as much as ∼ 1.2 eV between sites on the same edge. The incrementally increasing hydrogen coverage is seen to mainly weaken the adsorption, but intriguingly for certain configurations a stabilizing effect is also observed. The strengthened binding is seen to be coupled with significant surface restructuring, most notably the splitting of terminal S 2 -dimers. Our work links the energetics of hydrogen adsorption on 2H-MoS 2 to both static and dynamic geometrical features and quantifies the observed trends as a function of H-coverage, thus illustrating the complex structure/activity relationships of the MoS 2 catalyst. The results of this systematical study aims to serve as guidance for experimentalists by suggesting feasible edge/S-coverage combinations, the synthesis of which would potentially yield the most optimally performing HER-catalysts.

On the Synthesis of Morphology‐Controlled Transition Metal Dichalcogenides via Chemical Vapor Deposition for Electrochemical Hydrogen Generation

“…TMDs, especially MoS 2 , are well researched for their catalytic activity, particularly for their electro‐/photo‐electrocatalytic hydrogen generation (HER) . Though thermodynamically many TMDs favor HER (Δ G H ≈ 0 eV), their catalytic activity is limited kinetically due to the basal plane's inactivity . To circumvent this issue, either the basal plane has to be made active or more edge exposure needs to be achieved for enhancing the exchange current density .…”

Hydrogen adsorption trends on Al-doped Ni2P surfaces for optimal catalyst design

“…We study Al doping at substitutional Ni sites following the procedures of our recent studies on MoS 2 and doped MoS 2 . 11,21 We calculate formation energies of the substitutional dopants and analyze how the surfaces change in terms of H adsorption characteristics. Particularly we find evidence that Al doping changes the H adsorption landscape beneficially, which correlates with the experimentally observed improved activity.…”

Hydrogen adsorption on doped MoS2 nanostructures

“…Importantly, each geometrically and chemically different part may correspond to specific HER efficiency. The undoped, pristine basal plane of 2H-MoS 2 is understood to be inactive 4 , 13 , 17 . Several theoretical studies have been devoted to the pristine Mo and S-edges of MoS 2 in terms of Δ G H .…”