The origin of the mediocre methanol selectivity of Cu/ZnO-based catalysts for methanol synthesis from CO₂ hydrogenation

Cu/ZnO-based catalysts have been extensively and intensively studied for CO₂ hydrogenation to methanol due to their relatively superior catalytic performance. However, the mediocre methanol selectivity over Cu/ZnO-based catalysts has not been disclosed mainly because the predominant by-product CO formation activity fails to arouse any attention, significantly deterring the further catalyst optimization. The ZnOx-Cu nanoparticles (NP)-ZnO interface, derived from strong metal-support interactions (SMSI), has been recognized to be more active for methanol formation compared with the classical direct contact Cu-ZnO interface. In order to disclose the origin of the mediocre methanol selectivity, these two types of Cu-ZnO interfaces have been designed and constructed through carefully manipulating the synthesis and heat pre-treatment conditions of the powder model catalysts. Then, methanol and CO formation behaviors over these two interfaces have been explored thoroughly in actual reaction conditions. Finally, the origin of the mediocre methanol selectivity over Cu/ZnO-based catalysts has been proposed. This work provides unique insights for designing efficient Cu/ZnO-based catalysts with high methanol selectivity and yield and puts forward an effective strategy to investigate the catalytic behaviors over different interfaces in actual reaction conditions.