Co3O4/TiO2 Nanocomposite Formation Leads to Improvement in Ultraviolet–Visible-Infrared-Driven Thermocatalytic Activity Due to Photoactivation and Photocatalysis–Thermocatalysis Synergetic Effect
journal contributionposted on 21.10.2018 by Zhengkang Shi, Lan Lan, Yuanzhi Li, Yi Yang, Qian Zhang, Jichun Wu, Gequan Zhang, Xiujian Zhao
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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 °C. Compared to pure TiO2, the Co3O4/TiO2 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 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.