A synergetic effect between a single Cu site and S vacancy on an MoS2 basal plane for methanol synthesis from syngas

Abstract

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.