Evolution of copper species during heat treatment and its effect on CO oxidation reaction on CuCeZrOy catalyst synthesized by a facile solvent-free route

Abstract

Several ternary oxides CuCeZrOy (CCZ) were synthesized by a facile grinding method followed by calcination at high temperatures, and used as catalysts for CO oxidation at low temperatures. The influences of calcination temperature (400–600 °C) on the physicochemical properties of the as-synthesized ternary oxides were investigated by thermogravimetric analysis/differential scanning calorimetry (TGA/DSC), X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman, inductively coupled plasma-optical emission spectrometry (ICP-OES), N2 adsorption, H2-temperature programmed reduction (H2-TPR), and X-ray photoelectron spectroscopy (XPS) characterizations. The results show that the increase in calcination temperature from 400 to 500 °C is conducive to the high dispersion of CuOx on catalyst surface and the incorporation of Cu species into the support to form the Cu–Ce–Zr–O solid solution. Further raising of calcination temperature from 500 to 600 °C, however, leads to the segregation of Cu species from the solid solution to aggregate on support surface and growth of highly dispersed CuOx nanoparticles. The highest catalytic activity is acquired over the CCZ calcined at 500 °C, which can be ascribed to the largest contents of Cu+ species and oxygen vacancies owing to the formation of the maximum amount of Cu–Ce–Zr–O solid solution.