Facile synthesis of CuCo spinel composite oxides for toluene oxidation in air

A series of CCOx (x = 0, 1, 3 and 5) CuCo spinel composite oxides were prepared with different oxalic acid ratio by a facile, time-saving and green grinding-complexation method. The prepared spinel oxides were used to investigate the catalytic oxidation of toluene in air, which is a typical volatile organic compound (VOC). X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), Scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), H2-Temperature programmed reduction (H2-TPR) and O2-Temperature programmed desorption (O2-TPD) were used to characterize physicochemical properties of prepared CCOx spinel composite oxides. The characterization results show that Cu cations can dissolve into Co3O4 lattice to form CuCo2O4 spinel oxides. The participation of oxalic acids can more favor formation of CuCo2O4 spinel oxides, which promotes more active Co3+ species exposed on the surface and larger amount of adsorbed active oxygen species on CCOx spinel composite oxides. Meanwhile, larger specific surface area has been obtained for the CCOx spinel oxides. As a result, the low-temperature reducibility and O2 adsorption ability are significantly improved. Under the synergetic effects of above-mentioned factors, CCO3 spinel oxide catalyst exhibits the superior catalytic activity for achieving toluene conversion of 90% at 250 °C. This work indicates that the CuCo spinel composite oxide is a promising candidate for toluene catalytic oxidation in air, and grinding-complexation method provide a green, simple and time-saving way for preparation composite metal oxides.