Sodium-assisted MoS2 for boosting CO2 hydrogenation to methanol: The crucial role of sodium in defect evolution and modification

Abstract

The effective conversion of CO to methanol utilizing green hydrogen under moderate conditions represents a promising approach for achieving carbon neutrality. MoS demonstrates exceptional catalytic performance at temperatures below 200 °C, however, generating in-plane sulfur defects is challenging due to the intact planar structure. Introducing heteroatoms to induce sulfur vacancy formation and modulate their chemical environment remains a significant obstacle. In this study, we developed a NaCl-assisted method for synthesizing MoS and discovered that a small quantity of sodium not only promotes the formation of sulfur vacancies during the induction period, but also encourages CO hydrogenation via the carboxylate route, as opposed to the CO dissociation to CO* route over non-modified sulfur vacancies. Furthermore, catalysts at various stages throughout the 60 h induction period were characterized, revealing that the increase in sulfur vacancies and enhanced H dissociation capability are primary factors contributing to improved methanol yield. The sodium-modified MoS achieves a methanol space–time yield of up to 571 mg g h at 200 °C and 5 MPa with a 4.8% CO conversion and 96% methanol selectivity. The turnover frequency based on total sulfur vacancies reaches 170 h. This research is anticipated to offer a new strategy for enhancing the catalytic performance of CO hydrogenation to methanol using heteroatom-assisted defect engineering.