Highly efficient Cu/CeO2-hollow nanospheres catalyst for the reverse water-gas shift reaction: Investigation on the role of oxygen vacancies through in situ UV-Raman and DRIFTS

Abstract

Self-assembled CeO2 with 3D hollow nanosphere, nanoparticle and nanocube morphologies were prepared and used to support Cu particles. The obtained samples (denoted as Cu/CeO2-hs, Cu/CeO2-np and Cu/CeO2-nc, respectively) were tested for the reverse water-gas shift (RWGS) reaction. Under the reaction conditions, V(H2):V(CO2) = 3:1 and weight hourly space velocity (WHSV) = 300,000 mL g−1 h−1, the Cu/CeO2-hs sample exhibited the best catalytic performance among the as-prepared catalysts. In order to reveal the key factors affecting the catalytic performance, the physicochemical properties of the catalysts were analyzed by XRD, BET, SEM, TEM, H2-TPR, quasi in-situ XPS and in situ UV-Raman techniques. The results point out that the particle size of Cu is not the rate-determining factor while the amount of surface oxygen vacancies is highly correlated with the catalytic reaction rate. In situ UV-Raman and in situ DRIFTS experiments indicate the formation of bidentate carbonate and formate species on oxygen vacancy sites which is thought to be the key intermediates for the RWGS reaction. These findings unravel the crucial roles of surface oxygen vacancies on CO2 adsorption and activation and also highlight a feasible way for the design of highly efficient catalysts for the important RWGS reaction in chemical industry.