Synergetic Effect between Single Cu Site and S Vacancy on MoS2 Basal Plane for Methanol Synthesis from Syngas

Undercoordinated Mo or S atoms at the MoS2 edges have been identified as active sites for many catalytic reactions, while the basal plane with the largest density of sites is always inert. Taking advantage of the site abundance of the MoS2 basal plane requires revealing the origin of its low activity and development of strategies for activity enhancement, and remains a significant challenge. Using density functional theory calculations and microkinetic modeling, we show that the low activity and CH3OH selectivity of CO hydrogenation on the MoS2 basal plane mainly originates from O poisoning. By the synergetic effect between a single Cu site and adjacent S vacancy, O is substantially destabilized on the basal plane of MoS2. This not only provides more adsorbate-free active sites to activate reactants, but also facilitates an O removal reaction, leading to a five orders of magnitude higher CO hydrogenation rate than that on the MoS2 basal plane at 530 K and 50 bar and an H2/CO ratio of 3. Moreover, the destabilized O also inhibits CHO decomposition, which switches the product selectivity from 98% CH4 to 77% CH3OH. This work highlights the synergetic effect on enhancing the activity and selectivity of the MoS2 basal plane, achieving fundamental insight that can be used to design non-precious metal catalysts for methanol synthesis from syngas and other important reactions of technological interest.