Co3O4/TiO2 Nanocomposite Formation Leads to Improvement in Ultraviolet-Visible-Infrared-Driven Thermocatalytic Activity Due to Photoactivation and Photocatalysis-Thermocatalysis Synergetic Effect

Co3O4/TiO2 nanocomposites with different Co/Ti molar ratios were prepared by hydrolysis of cobalt acetate with urea in the presence of TiO2, and then calcined at 260 degrees C. Compared to pure TiO2, the Co3O4/TiO2 nano composite with the optimum Co/Ti molar ratio of 0.30 demonstrates significantly enhanced catalytic activity as well as excellent catalytic durability for abatement of refractory poisonous benzene (a typical air pollutant) with ultraviolet-visible-infrared (UV-vis-IR) irradiation. It also exhibits effective catalytic activity for benzene abatement even with lambda > 830 nm IR irradiation. Its very high catalytic activity derives from light-driven thermocatalytic benzene oxidation on nano Co3O4 in the Co3O4/TiO2 nanocomposite. A novel synergetic effect among light-driven thermocatalysis on Co3O4 and UV photocatalysis on TiO2 in the Co3O4/TiO2 nanocomposite is discovered to remarkably promote catalytic activity and improve catalytic durability by inhibiting the formation of refractory carbonaceous intermediates on TiO2 by photocatalysis: energetic species produced by UV photocatalysis on TiO2 move from TiO2 to Co3O4 through the interface between nano Co3O4 and TiO2, thus accelerating the light-driven thermocatalytic benzene oxidation on nano Co3O4. A novel photoactivation, completely different from photocatalysis on TiO2, is discovered to further considerably accelerate light-driven thermocatalytic activity of Co3O4: Irradiation not only promotes the activity of lattice oxygen of nano Co3O4 but also accelerates the reoxidation of the reduced cobalt oxide (Co3O4-x), resulting in a considerable enhancement in the light-driven thermocatalytic activity of Co3O4. The light-driven themocatalysis together with the novel photocatalysis-thermocatalysis synergetic effect and photoactivation in the Co3O4/TiO2 nanocomposite cause a tremendous enhancement of 489 times in benzene mineralization rate (initial production rate of CO2) as compared to the photocatalytic benzene abatement under UV-vis-IR irradiation with the same light intensity at near room temperature.