Mn-promoted MoS 2 catalysts for CO 2 hydrogenation: enhanced methanol selectivity due to MoS 2 /MnO x interfaces.

Considering the alarming scenario of climate change, CO 2 hydrogenation to methanol is considered a key process for phasing out fossil fuels by means of CO 2 utilization. In this context, MoS 2 catalysts have recently shown to be promising catalysts for this reaction, especially in the presence of abundant basal-plane sulfur vacancies and due to synergistic mechanisms with other phases. In this work, Mn-promoted MoS 2 prepared by a hydrothermal method presents considerable selectivity for CO 2 hydrogenation to methanol in comparison with pure MoS 2 and other promoters such as K and Co. Interestingly, if CO is used as a carbon source for the reaction, methanol production is remarkably lower, which suggests the absence of a CO intermediate during CO 2 hydrogenation to methanol. After optimization of synthesis parameters, a methanol selectivity of 64% is achieved at a CO 2 conversion of 2.8% under 180 °C. According to material characterization by X-ray Diffraction and X-ray Absorption, the Mn promoter is present mainly in the form of MnO and MnCO 3 phases, with the latter undergoing convertion to MnO upon H 2 pretreatment. However, following exposure to reaction conditions, X-ray photoelectron spectroscopy suggests that higher oxidation states of Mn may be present at the surface, suggesting that the improved catalytic activity for CO 2 hydrogenation to methanol arises from a synergy between MoS 2 and MnO x at the catalyst surface.