Generating Strong Metal-Support Interaction and Oxygen Vacancies in Cu/MgAlO_x Catalysts by CO₂ Treatment for Enhanced CO₂ Hydrogenation to Methanol

Strong metal-support interactions (SMSIs) are essential for optimizing the performance of supported metal catalysts by tuning the metal-oxide interface structures. This study explores the hydrogenation of CO₂ to methanol over Cu-supported catalysts, focusing on the synergistic effects of strong metal-support interaction (SMSI) and oxygen vacancies introduced by the CO₂ treatment to the catalysts on the catalytic performance. Cu nanoparticles were immobilized on Mg-Al layered double oxide (LDO) supports and modified with nitrate ions to promote oxygen vacancy generation. Further calcination in a 15% CO₂/85% N₂ atmosphere at various temperatures not only resulted in the formation of SMSI and electronic metal-support interaction (EMSI) between Cu and MgO, but also generated abundant oxygen vacancies on MgO. The optimized 7.5%Cu/MA-C700 catalyst (Cu supported on MgAl-LDO treated in CO₂ at 700 °C) exhibited significantly higher methanol production and turnover frequency compared to the air-calcined counterparts. In situ FTIR studies further revealed that oxygen vacancies led to the formation of more monodentate formate species, thus enhancing methanol production. This research provides a novel approach to engineering the catalyst interface structure and the interaction between the active metal and the support, particularly for the irreducible metal oxide support, for efficient hydrogenation of CO₂ to methanol.