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

Abstract

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 TOFmethanol 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. Keywords: Morphology, Cu/ZnO, CO2 hydrogenation, Methanol, Synergy