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

The effective conversion of CO2 to methanol utilizing green hydrogen under moderate conditions represents a promising approach for achieving carbon neutrality. MoS2 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 MoS2 and discovered that a small quantity of sodium not only promotes the formation of sulfur vacancies during the induction period, but also encourages CO2 hydrogenation via the carboxylate route, as opposed to the CO2 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 H2 dissociation capability are primary factors contributing to improved methanol yield. The sodium-modified MoS2 achieves a methanol space–time yield of up to 571 mgMeOH gcat−1h−1 at 200 °C and 5 MPa with a 4.8 % CO2 conversion and 96 % methanol selectivity. The turnover frequency based on total sulfur vacancies reaches 170 h−1. This research is anticipated to offer a new strategy for enhancing the catalytic performance of CO2 hydrogenation to methanol using heteroatom-assisted defect engineering.