Density Functional Theory Study of S-Edge Structures, Thiophene Adsorption, and Hydrodesulfurization Mechanisms on Triangular MoS2 Nanoclusters

Edge structures, thiophene adsorption and hydrodesulfurization (HDS) mechanisms are investigated on the S-edge of triangular MoS2 nanoclusters using density functional theory. The calculated formation energies for different S coverages on the S-edge suggest that the formation of coordinative unsaturated site at the vertex and edge-I (close to the vertex) sites is preferred over the edge-II (away from the vertex) sites. The adsorption of thiophene on the top site of Mo atom mainly occurs at the edge-I, whereas bridge adsorption occurs at the edge-II. The 92% and 50% S-edge coverages involve relatively larger adsorption energies (- 0.68 and - 0.79 eV) among all the possible adsorption configurations. On the S edge with 92% S coverage, the hydrogenation route is more favorable, producing 1-butene. On the S edge with 50% S coverage, the direct desulfurization route is preferred, yielding butadiene. These findings deepen the understanding of edge structures of MoS2 nanoclusters and the corresponding HDS mechanisms for MoS2-based HDS catalysts.{GRAPHIACAL ABSTRACT}