Exploring the Reaction Mechanism of H2S Decomposition with MS3 (M = Mo, W) Clusters

H 2 S is abundantly available in nature, and it is a common byproduct in industries. Molybdenum sulfides have been proved to be active in the catalytic decomposition of hydrogen sulfide (H 2 S) to produce hydrogen. In this study, density functional theory (DFT) calculations are carried out to explore the reaction mechanisms of H 2 S with MS 3 (M = Mo, W) clusters. The reaction mechanism of H 2 S with MoS 3 is roughly the same as that of the reaction with WS 3 , and the free-energy profile of the reaction with MoS 3 is slightly higher than that of the reaction with WS 3 . The overall driving forces (-Δ G ) are positive, and the overall reaction barriers (Δ G b ) are rather small, indicating that such H 2 productions are product-favored. MS 3 (M = Mo, W) clusters have clawlike structures, which have electrophilic metal sites to receive the approaching H 2 S molecule. After several hydrogen-atom transfer (HAT) processes, the final MS 4 ·H 2 (IM-4) complexes are formed, which could desorb H 2 at a relatively low temperature. The singlet product MS 4 clusters contain the singlet S 2 moiety, similar to the adsorbed singlet S 2 on the surface of sulfide catalysts. The theoretical results are compared with the experiments of heterogeneous catalytic decomposition of H 2 S by MoS 2 catalysts. Our work may provide some insights into the optimal design of the relevant catalysts.