Highly efficient UV-Vis-infrared catalytic purification of benzene on CeMnxOy/TiO2 nanocomposite, caused by its high thermocatalytic activity and strong absorption in the full solar spectrum region

Abstract

The nanocomposite of amorphous cerium manganese oxide supported on nano TiO₂ (CeMn_xO_y/TiO₂) was prepared by the facile hydrothermal redox reaction of Ce(NO₃)₃ and KMnO₄ in the presence of nano TiO₂. The CeMn_xO_y/TiO₂ nanocomposite was characterized by XRD, TEM, SEM, EDX, XPS, BET, CO-TPR, and diffusive reflectance UV-Vis-IR absorption. It exhibits efficient thermocatalytic activity for the oxidation of the carcinogenic and recalcitrant benzene, which is comparable to that of the expensive noble metal catalyst (0.5% Pt/Al₂O₃), and is much higher than the CeO₂/TiO₂ and MnO_x/TiO₂ nanocomposites with the same metal/Ti molar ratio. Its specific CO₂ production rate (r_CO2) at 220 °C (88.6 μmol g⁻¹ min⁻¹) is 6.3 and 7.5 times higher than the nanocomposites of CeO₂/TiO₂ and MnO_x/TiO₂, respectively. The highly efficient thermocatalytic activity of the CeMn_xO_y/TiO₂ nanocomposite is attributed to its higher oxygen activity, compared to the nanocomposites of CeO₂/TiO₂ and MnO_x/TiO₂. Remarkably, the CeMn_xO_y/TiO₂ nanocomposite can be driven by simulated solar light for benzene oxidation. It exhibits highly efficient catalytic activity with the irradiation of the full solar spectrum, visible-infrared, and infrared light. Its initial CO₂ production rate is 117.0, 94.8 and 37.9 μmol g⁻¹_catalyst min⁻¹, under the irradiation of the full solar spectrum, visible-infrared light with wavelength above 420 nm, and infrared light with wavelength above 830 nm, respectively. This is attributed to the fact that the CeMn_xO_y/TiO₂ nanocomposite efficiently transforms the absorbed solar energy into thermal energy, due to its strong absorption in the full solar spectrum region, resulting in a significant increase in its temperature above its light-off temperature, for the thermocatalytic oxidation of benzene.