Enhancing CO2 hydrogenation to methanol via the synergistic effect of MoS2 interlayer spacing and sulfur vacancies

Abstract

The hydrogenation of carbon dioxide (CO₂) to methanol is an important reaction to convert CO₂ into valuable products and reduce carbon emission. MoS₂ is an effective catalyst for CO₂ hydrogenation, but the synergistic effects of interlayer spacing expansion and surface sulfur vacancy strengthening have not been studied systematically. Here, this work reports hydrazine hydrate as an effective reducing agent for MoS₂. The reducing agent can not only expand the interlayer spacing of MoS₂, but also increase the concentration of sulfur vacancies through a simple treatment. More importantly, the synergistic effect between the interlayer spacing and sulfur vacancies of MoS₂ significantly increases the methanol space-time yield (STY). At 220 °C, 4 MPa, and 8000 mL g_cat⁻¹ h⁻¹, the MoS₂–N₂H₄-4 catalyst exhibits 76.8% methanol selectively, 5.52% CO₂ conversion, and a high methanol STY of up to 0.1214 g g_cat⁻¹ h⁻¹ and lasts for at least 200 h. The structure–performance relationship was further studied using physio-chemical characterization and DFT. These results provide valuable insights into the development of highly efficient MoS₂ catalysts for CO₂ hydrogenation.