Promotion Effect Of Metal Oxides On Inverse CeO₂/CuO Catalysts For Preferential Oxidation Of Co

Hydrogen has been considered as the most potentially strategic and clear energy in the21st century. The development of fuel cells is one of the ideal hydrogen conversion devices, which promotes the development of hydrogen technology. One of the most typical applications is the proton exchange membrane fuel cell (PEMFC). However, the0.5-1.0vol%CO in the hydrogen feed gas degrades the performance of the electrodes which are highly sensitive to the presence of even traces of CO. Hence, it is essential to keep the CO concentration below100ppm in the hydrogen. The preferential oxidation of CO is a simple and cost effective technique for performing this ultimate CO removal. CuO-CeO2catalysts have been investigated extensively in recent years from an economical point of view, and also have shown promising catalytic performance for CO oxidation.In this work, a series of inverse M-CeO2/CuO (M=metallic oxide) catalysts were prepared in order to explore influences of the metallic oxide on the catalytic performance of the CeO2/CuO catalysts. The crystalline structure and properties of the catalysts were characterized by XRD, H2-TPR, SEM, TEM/HRTEM, XPS, ICP and N2adsorption-desorption techniques. The main contents of the work are as follows:The inverse CeO2/CuO catalysts with different-ratio of Ce1Cu2SnxTix were prepared by the hydrothermal method. The study shows that catalytic activity of the catalysts low temperature has been improved after the doping of Sn-Ti composite oxide. However, the surface area of catalysts decreases after introduction of the Sn-Ti oxide since the crystallinity of the catalysts increases. The Ce1Cu2Sn0.25Ti0.25catalyst has the best catalytic activity among the group of the catalysts.The MOx-CeO2/CuO (M=Co, Mn, Sn and Zn) catalysts were prepared by the hydrothermal method in order to improve low-temperature activity of the CeO2/CuO catalyst and further widen the temperature window of full CO conversion. It is found that the filamentous-like oxides are selfassembled CeO2, and the particle-like oxides consist of CeO2and CuO. The MnO2can improve the textural property of CeO2/CuO catalyst. The MnO2-CeO2/CuO catalyst exhibits the best activity from75℃to115℃, suggesting that the addition of Mn is the most effective for improving low-temperature activity of the CeO2/CuO catalyst.The MOx/CeO2-CuO (M=Fe, Co, Ni) catalysts were prepared by the precipitation method. The study shows that MOX is homogeneously distributed in the catalysts and the addition of Fe, Co and Ni decreases the average crystallite sizes of CeO2and CuO, increases the BET surface area of CeO2-CuO catalyst and improves the formation of Ce3+on the surface. The NiO/CeO2-CuO catalyst exhibits the highest catalytic activity and widest temperature window of complete CO conversion. The reason is small average crystallite sizes, high BET surface area as well as good dispersion of CeO2, high concentration of Ce3+and the reduced copper species on the surface. The deactivation of NiO/CeO2-CuO is from the decrease of interaction between CuO and and the amount of lattice oxygen.