Manganese oxides and iron-manganese oxides supported on TiO2 were prepared by the sol-gel method and used for low-temperature selective catalytic reduction (SCR) of NO with NH3. Base on the previous study, Mn(0.4)/ TiO2 and Fe(0.1)-Mn(0.4)/TiO2 were then selected to carry out the in situ diffuse reflectance infrared transform spectroscopy (DRIFT) investigation for revealing the reaction mechanism. The DRIFT spectroscopy for the adsorption of NH3 indicated the presence of coordinated NH3 and NH4+ on both of the two catalysts. When NO was introduced, the coordinated NH3 on the catalyst surface was consumed rapidly, indicating these species could react with NO effectively. When NH3 was introduced into the sample preadsorbed with NO + O2, SCR reaction would not proceed on Mn(0.4)/TiO2. However, for Fe(0.1)-Mn(0.4)/ TiO2 the bands due to coordinated NH3 on Fe2O3 were formed. Simultaneously, the bidentate nitrates were transformed to monodentate nitrates and NH4+ was detected. And NO2 from the oxidation of NO on catalyst could react with NH4+ leading to the reduction of NO. Therefore, it was suggested that the SCR reaction on Fe(0.1)-Mn(0.4)/TiO2 could also take place in a different way from the reactions on Mn(0.4)/TiO2 proposed by other researchers. Furthermore, the SCR reaction steps for these two kinds of catalysts were proposed.

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Mesoporous C-doped TiO2 nanomaterials with an anatase phase are prepared by a one-pot green synthetic approach using sucrose as a carbon-doping source for the first time. A facile post-thermal treatment is employed to enhance visible light photocatalytic activity of the as-prepared photocatalyst. The enhancement effect of post-thermal treatment between 100 and 300 °C is proved by the photodegradation of gas-phase toluene, and the optimum temperature is 200 °C. Physicochemical properties of the samples are characterized in detail by X-ray diffraction, Raman spectroscopy, N2 adsorption–desorption isotherms, transmission electron microscopy, Fourier transform-infrared spectroscopy, X-ray photoelectron spectroscopy, UV–vis diffuse reflectance spectroscopy, and photoluminescence. The results indicate that the promotive effect of the post-thermal treatment can be attributed to the changes of the catalysts’ surface and optical properties. The results also show that the recombination of electron–hole pairs is effectively inhibited after thermal treatment due to the reduction of surface defects. The facile post-thermal treatment provides a new route for potential industrial applications of C-doped TiO2 nanomaterials prepared by a green approach owing to its low cost and easy scale-up.

Mesoporous C-doped TiO2 nanomaterials with anatase phase are synthesized by a one-step “green” synthetic approach with low-cost inorganic Ti(SO4)2 and glucose as precursors for the first time. This facile method avoids treatment at high temperature, use of expensive or unstable precursors, and production of undesirable byproducts in the synthesis process. The physicochemical properties of as-prepared samples are characterized in detail by X-ray diffraction (XRD), Raman spectroscopy (Raman), N2 adsorption−desorption isotherms, transmission electron microscopy (TEM), Fourier transform-infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TG), UV−vis diffuse reflectance spectroscopy (UV−vis DRS), and photoluminescence (PL). The results indicate that oxygen sites in the TiO2 lattice are substituted by carbon atoms and an O−Ti−C bond is formed. The observed new electronic states above the valence band edge are directly responsible for the electronic origin of the band gap narrowing and visible light photoactivity of the C-doped TiO2. Furthermore, the possible formation mechanism of mesoporous C-doped TiO2 is also discussed. The as-prepared C-doped TiO2 exhibits excellent visible light photocatalytic activity in degradation of toluene in the gas phase compared with that of commercial TiO2 photocatalyst (P25) and C-doped TiO2 prepared by the solid state method. The efficient activity can be attributed to the large surface area and pore volume. Our novel synthesis approach is energy-efficient and environmentally friendly, which can provide an effective approach for industrial applications owing to its low cost and easy scaling up.

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