Different metal (Mn, Fe, Co, Ni, and Zr) decorated Cu/CeO2 catalysts for efficient CO oxidation in a rich CO2/H2 atmosphere

Abstract

In this work, CuM/CeO₂ (M = Mn, Fe, Co, Ni, and Zr) catalysts with a low Cu content of 1 wt% were purposely designed and prepared using the co-impregnation method. The samples were characterized using various techniques (TG-DTA, XRD, N₂-adsorption/desorption measurements, H₂-TPR, XPS and Raman spectroscopy) and CO preferential oxidation (CO-Prox) under H₂/CO₂-rich conditions was performed. The results have shown that enhanced catalytic performance was achieved upon the introduction of Mn, Co and Ni, and little impact was observed with Zr doping, but Fe showed a negative effect, as compared with the Cu/CeO₂ catalyst. Characterization data revealed that the M doping strongly changed the surface composition, revealing the decreased Cu/Ce ratios on the surface, which could be accounted for by the formation of more M/Cu–O–Ce solid solution, or strong Cu–M interactions. When Mn was used, the obtained CuMn/CeO₂ catalyst revealed the highest concentration of the oxygen vacancies and Ce³⁺ ions, which could be correlated well with its superior catalytic performance. Compared with the Cu/CeO₂ catalyst, the CO conversion rate increased by 24.7% at a low temperature of 90 °C over the CuMn/CeO₂ catalyst. At 130 °C, the maximum CO conversion was 94.7% and the CO₂ selectivity was 78.9%. Conversely, the Fe doped Cu/CeO₂ catalyst demonstrated the poorest catalytic activity, which was due to the blockage effect of Fe species on Cu showing a high Fe/Cu ratio of 1.9 on the surface.