Strained few-layer MoS₂ with atomic copper and selectively exposed in-plane sulfur vacancies for CO₂ hydrogenation to methanol.

Abstract

In-plane sulfur vacancies (Sv) in molybdenum disulfide (MoS₂) were newly unveiled for CO₂ hydrogenation to methanol, whereas edge Sv were found to facilitate methane formation. Thus, selective exposure and activation of basal plane is crucial for methanol synthesis. Here, we report a mesoporous silica-encapsulated MoS₂ catalysts with fullerene-like structure and atomic copper (Cu/MoS₂@SiO₂). The main approach is based on a physically constrained topologic conversion of molybdenum dioxide (MoO₂) to MoS₂ within silica. The spherical curvature enables the generation of strain and Sv in inert basal plane. More importantly, fullerene-like structure of few-layer MoS₂ can selectively expose in-plane Sv and reduce the exposure of edge Sv. After promotion by atomic copper, the resultant Cu/MoS₂@SiO₂ exhibits stable specific methanol yield of 6.11 mol_MeOH mol_Mo^-1 h^-1 with methanol selectivity of 72.5% at 260 °C, much superior to its counterparts lacking the fullerene-like structure and copper decoration. The reaction mechanism and promoting role of copper are investigated by in-situ DRIFTS and in-situ XAS. Theoretical calculations demonstrate that the compressive strain facilitates Sv formation and CO₂ hydrogenation, while tensile strain accelerates the regeneration of active sites, rationalizing the critical role of strain.