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

Co 3 O 4 /TiO 2 nanocomposites with different Co/Ti molar ratios were prepared by hydrolysis of cobalt acetate with urea in the presence of TiO 2, and then calcined at 260 °C. Compared to pure TiO 2, the Co 3 O 4 /TiO 2 nanocomposite 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 λ > 830 nm IR irradiation. Its very high catalytic activity derives from light-driven thermocatalytic benzene oxidation on nano Co 3 O 4 in the Co 3 O 4 /TiO 2 nanocomposite. A novel synergetic effect among light-driven thermocatalysis on Co 3 O 4 and UV photocatalysis on TiO 2 in the Co 3 O 4 /TiO 2 nanocomposite is discovered to remarkably promote catalytic activity and improve catalytic durability by inhibiting the formation of refractory carbonaceous intermediates on TiO 2 by photocatalysis: energetic species produced by UV photocatalysis on TiO 2 move from TiO 2 to Co 3 O 4 through the interface between nano Co 3 O 4 and TiO 2, thus accelerating the light-driven thermocatalytic benzene oxidation on nano Co 3 O 4 . A novel photoactivation, completely different from photocatalysis on TiO 2, is discovered to further considerably accelerate light-driven thermocatalytic activity of Co 3 O 4: Irradiation not only promotes the activity of lattice oxygen of nano Co 3 O 4 but also accelerates the reoxidation of the reduced cobalt oxide (Co 3 O 4– x ), resulting in a considerable enhancement in the light-driven thermocatalytic activity of Co 3 O 4 . The light-driven themocatalysis together with the novel photocatalysis–thermocatalysis synergetic effect and photoactivation in the Co 3 O 4 /TiO 2 nanocomposite cause a tremendous enhancement of 489 times in benzene mineralization rate (initial production rate of CO 2 ) as compared to the photocatalytic benzene abatement under UV–vis-IR irradiation with the same light intensity at near room temperature.