Spinel Co3O4 oxides-support synergistic effect on catalytic oxidation of toluene

Bulk spinel Co3O4 oxide and supported Co3O4 catalysts (Co3O4/YSZ and Co3O4/TiO2) were synthesized by one-step hydrothermal method. Their physicochemical properties were characterized by inductively coupled plasma optical emission spectroscopy, N-2-sorption, powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, hydrogen-temperature programmed reduction and X-ray photoelectron spectroscopy.These characterization strategies were applied to corroborate and better understand the interaction between Co3O4 and the supports induced by the synergistic effect of support and the subsequent catalytic performance in toluene oxidation. The catalytic stability was evaluated by three consecutive runs and a long-term test. A highest toluene catalytic activity was achieved over Co3O4/YSZ supported catalyst comparing to that of the bulk Co3O4 and Co3O4/TiO2 catalysts, which could be attributed to its better low-temperature reducibility, oxygen activation and mobility induced by the intrinsic support properties. Thus, the positive interaction between spinel Co3O4 phase and YSZ support promoted the intrinsic catalytic properties for toluene oxidation, which was verify by testing a dual catalyst bed system consisting of bulk Co3O4 catalyst and YSZ support beds. These results were further confirmed by temperature-programmed oxygen isotopic exchange experiments, which indicated that the activation and diffusion of oxygen species on the YSZ oxygen vacancy sites were promoted by Co3O4, resulting in a significant increase of the reaction rate for toluene oxidation.