UiO-66-derived Ce/Ni-ZrO2 nano-catalysts with a large nickel surface area for the highly efficient CO2 methanation under high GHSVs

Abstract

In this work, a new preparation method is developed for the preparation of Ce/Ni-ZrO2 nano-catalyst (Ce/Ni-ZrO2-N). Although similar catalytic systems have been studied by many others, there is still a need for improvement in terms of nickel surface area, catalytic efficiency, and insights of the mechanism. The Ce/Ni-ZrO2-N developed in this study exhibits a large nickel surface area (50.6 m2∙g−1) and a small nickel particle size (∼5.1 nm). During the preparation of such a catalyst, UiO-66 is used not only as a precursor for the preparation of ZrO2 with a large surface area but also as a dispersant for confining nickel nanoparticles. The catalyst demonstrates an excellent catalytic performance at high GHSVs. With a 16-fold increase in GHSVs, the CO2 conversion of Ce/Ni-ZrO2-N only decreases by 32.1 %, whereas that of the control group drops by 50.3 %. This is attributed to the high nickel surface area and relatively low activation energy. Moreover, the characterization and Density Functional Theory (DFT) studies reveal that electron transfer from Ce to Ni enhances the activation of CO2 on the Ni sites, which subsequently contributes to a better catalytic performance. In addition, the catalyst shows excellent anti-coking ability during the 40 h's testing, which, according to DFT calculations, is attributed to the high energy barrier for coke formation on the active sites.