CO_(2)hydrogenation to methanol promoted by Cu and metastable tetragonal Ce_(x)Zr_(y)O_(z) interface

Designing effective catalyst to improve the activity of CO_(2) hydrogenation to methanol is a potential avenue to realize the utilization of CO_(2) resources. Herein we construct three kinds of Cu/Ce_(x)Zr_(y)O_(z)(CCZ) catalysts with different crystal phases of Ce_(x)Zr_(y)O_(z)solid solutions, which demonstrate distinct activity and methanol selectivity in the order of metastable tetragonal-CCZ(CCZ-t’’, parts of oxygen in Ce_(x)Zr_(y)O_(z) were replaced by tetragonal phase from cubic fluorite phase) > tetragonal-CCZ(CCZ-t) > cubic-CCZ(CCZ-c) for CO_(2) hydrogenation to methanol. Structural analysis reveals that oxygen vacancies, surface hydroxyls and unsaturated Cu species of CCZ all follow the same sequence as that of activity and methanol selectivity,indicating that the above features are beneficial to improve the catalytic reaction performance.Temperature programmed experiments and mechanism studies show that the interface between Cu and tetragonal(t and t’’) Ce_(x)Zr_(y)O_(z) can promote CO_(2) adsorption, and the adsorbed CO_(2) is more reactive and can generate active bidentate carbonate species, which can be hydrogenated to form active monodentate and bidentate formate species under CO_(2) and H_(2) atmosphere. These intermediates should be crucial to the formation of methanol product. CCZ-t’’has stronger H_(2) activation ability than CCZ-t, which makes the former catalyst have more intermediates and higher methanol selectivity. In contrast, CO_(2) mainly adsorbs on cubic Ce_(x)Zr_(y)O_(z) support of CCZ-c, but its H_(2) spillover ability is low, which hinders the reaction process. In addition, the strong adsorption of surface intermediates on CCZ-c is also not conducive to methanol formation. Results here demonstrate that constructing active Cu-support interfaces may be an important approach to design effective catalyst for CO_(2)hydrogenation.