Few-layer MoS2 dispersion induced by sulfur atom sharing to promote CO2 hydrogenation to methanol.

With the ongoing interest in developing more stable and versatile catalysts for CO2 hydrogenation to methanol, molybdenum sulfide (MoS2) has been recently proposed as an alternative material. However, in its bulk state, CO2 hydrogenation over MoS2 typically favors methane formation. In this work, a wet impregnation method is applied for the production of ZnS-supported MoS2, as confirmed by characterization via X-ray Diffraction, Raman and X-ray Photoelectron Spectroscopy. In contrast with the negligible methanol production shown by the pure MoS2 reference, 2% MoS2/ZnS presents a methanol selectivity of 78% at a CO2 conversion of 2.3% under the mild reaction conditions of 200 °C and 20 bar. Density Functional Theory and Transmission Electron Microscopy suggest that the improved catalytic activity arises from an even dispersion of few-layer MoS2 with exposed basal plane sites at the ZnS surface, an arrangement possibly enabled by the structural similarity and the shared S atoms between 2H-MoS2 and W-ZnS phases. This hypothesis is strengthened by the comparison with the reference sample consisting of ZrO2-supported MoS2 sample, in which more agglomerated MoS2 particles resulted in a lower and less selective methanol production. Moreover, in situ X-ray absorption spectroscopy and H2 temperature-programmed reduction suggest further evidence of a MoS2/ZnS interaction during the H2 pretreatment, which may promote not only the expected formation of S-vacancies but also a partial reconstruction of MoS2 given the close contact and sharing of S atoms with the ZnS support.