Effect of tungsten oxide on ceria nanorods to support copper species as CO oxidation catalysts

Abstract

In this work, tungsten oxide with different concentrations (0, 0.4 at%, 2.0 at% and 3.2 at%) was introduced to the ceria nanorods via a deposition-precipitation (DP) approach, and copper species of ca. 10 at% were sequentially anchored onto the modified ceria support by a similar DP route. The aim of the study was to investigate the effect of the amount of tungsten oxide (0, 0.4 at%, 2.0 at%, and 3.2 at%) modifier on the copper-ceria catalysts for CO oxidation reaction and shed light on the structure-activity relationship. By the aids of multiple characterization techniques including N2 adsorption, high-resolution transmission electron microscopy (HRTEM), powder X-ray diffraction (XRD), X-ray absorption fine structure (XAFS), and temperature-programmed reduction by hydrogen (H2-TPR) in combination with the catalytic performance for CO oxidation reaction, it is found that the copper-ceria samples maintain the crystal structure of the fluorite fcc CeO2 phase with the same nanorod-like morphology with the introduction of tungsten oxide, while the textural properties (the surface area, pore volume and pore size) of ceria support and copper-ceria catalysts are changed, and the oxidation states of copper and tungsten are kept the same as Cu2+ and W6+ before and after the reaction, but the introduction of tungsten oxide (WO3) significantly changes the metal-support interaction (transfer the CuOx clusters to Cu-[Ox]-Ce species), which delivers to impair the catalytic activity of copper-ceria catalysts for CO oxidation reaction.