Morphology effect of ZnO support on the performance of Cu toward methanol production from CO2 hydrogenation

Recently, the chemical conversion of the greenhouse gas CO₂ into value-added methanol has been of great interest. To address this issue, ZnO nanorods were synthesized by a facile microwave assisted technique and selected as support in Cu/ZnO catalyst. Herein, structure-activity relationship of the as-prepared catalysts in CO₂ hydrogenation to methanol were elucidated in detail using different characterization technique including N₂ physisorption, XRD, TPR, TEM, XPS and insitu DRIFTS (CO chemisorption) etc. Interestingly, rodlike ZnO hosted the highly dispersed Cu species, stronger Cu-support interaction at the interface in comparison with another reference CuZn-C sample, which was supported on commercial ZnO. In particular, EPR and XPS analysis evidenced the direct electron transfer from ZnO support to Cu species in CuZn-R, thereby facilitating the formation of O vacancies. These positive factors could provide the extremely active sites for CO₂ hydrogenation and be correlated to the better catalytic activity. Indeed, the calculated TOF_methanol for CuZn-R was approximately ten times larger than that of CuZn-C sample. The results implied that the morphology structure of ZnO support, which could induce various crystal planes and amounts of defects and/or imperfections, possessed a critical role on the catalytic performance. This finding might shed light on the design of efficient catalysts for catalytic conversion of the undesirable CO₂.