Doping effect of transition metals (Zr, Mn, Ti and Ni) on well-shaped CuO/CeO2(rods): nano/micro structure and catalytic performance for selective oxidation of CO in excess H2

Abstract

A series of CuO/CeM(rod) catalysts doped by transition metals were prepared and systematically characterized. The introduction of Mn and Ti plays a significant role in promoting the catalytic performance of the CuO/CeO₂(rod) catalyst for the preferential oxidation of CO in H₂-rich gas, while the doping with Zr basically maintains the same catalytic activity and Ni leads to a negative influence. Mn and Ti additives remarkably enrich the formation of defect structures and promote copper ion incorporation into the surface of CeM(rod), which greatly facilitates the generation of strong interfacial copper–ceria interaction in CuO/CeMn(rod) and CuO/CeTi(rod). In addition, CuO/CeMn(rod) possesses excellent surface oxygen mobility at low temperature due to the existence of manganese species with multiple valence states and todorokite species. The Ce-doped perovskite structure (Na_0.5Ce_0.5TiO₃) further adjusts the oxygen vacancy in CuO/CeTi(rod) and anchors copper oxide species with strong interactions. Although a homogeneous solid solution is formed in CeZr(rod) with increased amounts of oxygen vacancies, the interaction between copper and ceria species in the interface of CuO/CeZr(rod) remains the same as with CuO/CeO₂(rod). The addition of Ni impairs the dispersion of copper oxide and weakens the copper–ceria interaction, which damages the catalytic performance of CuO/CeNi(rod).