Solid-supported metal catalysts have been widely used in industrial processes. The morphology of coated metal on the support is usually an important factor affecting the efficiency of the catalyst. In this study, a photocatalytic process is utilized to control the morphology of platinum particles deposited on titania (Degussa P-25). More specifically, the effect of pH on the morphology and the valence state of platinum nanoparticles was systemically investigated. It is found that, via a simple pH-controlled process, various states of platinum (Pt0, PtⅡO, or PtⅣO2) can be deposited onto the support directly at will. In this paper, the mechanism of morphology control and the key influencing factors at different pH regimes will be discussed. Followed by photodeposition, a H2 thermal treatment process was employed to convert the oxides into metal platinum with narrow size distribution and even coverage on the supporting titania. Various techniques such as transmission electron microscopy, high-resolution transmission electron microscopy, energy-dispersive analysis of X-rays, and X-ray photoelectron spectroscopy were employed to characterize the prepared titania-supported platinum particles.

Photocatalytic reduction of nitrate ions was examined by using Cu/MgTiO3-TiO2 catalyst in the presence of sodium oxalate as hole scavenger. Many factors such as catalyst calcination temperature, Cu: Mg atom molar ratio, different hole scavengers and different concentrations of sodium oxalate were tested to search for the optimal reaction conditions. X-ray diffraction (XRD) and Transmission Electron Micrograph (TEM) were performed to characterize the composite semiconductors catalyst. Our results indicated that Cu/MgTiO3-TiO2 catalyst calcined at 873K showed the highest photocatalytic activity and nitrate conversion reached 39.2% after 2 h irradiation. The enhanced effect for photocatalytic nitrate reduction activity was most likely to result from the formation of composite semiconductor MgTiO3-TiO2 and the transformation of TiO2 crystalline phase.

From the 27Al MAS NMR and 2D 3QMAS NMR experiments, it can be concluded that during the steaming process of zeolite omega, some part of the framework tetrahedral Al species are gradually distorted. The 30 ppm broad hump in the 1D 27Al spectra is mainly due to appearance of the distorted tetrahedral Al. With the dealumination process going on, penta-coordinated Al species are formed and contribute also to the 30 ppm broad hump. There exists the trend that the formation of penta-coordinated Al occurs with the consumption of the distorted tetrahedral Al species. Because the same phenomenon of the 27Al NMR signals has also been observed in other zeolites, such as mordenite, ZSM-5 and Y, it could be regarded as a general procedure in the process of dealumination of acidic zeolites.

Titania supported palladium-copper bimetallic catalysts (Pd-Cu/TiO2) are prepared by the liquid phase chemical reduction method and then applied in the liquid phase catalytic reduction of nitrate ions (NO3−). Compared with the conventional impregnation method that needs the post-thermal reduction to prepare the supported metallic catalysts, the liquid phase chemical reduction at room temperature can inhibit the aggregation of metal active components and have been proved to exhibit high catalytic activity in this work. The conversions of NO3− are 29.18% and 54.12% over the catalysts treated at 873 and 298 K, respectively. The conversion of NO3− and selectivity to N2 influenced by the effect of the support, the loading of Pd + Cu, the molar ratio of Pd to Cu, the H2 flow rate, the addition of CO2 and the pH value of solution are also discussed in detail with the surface characterizations by X-ray photoelectron spectrum (XPS), X-ray diffraction (XRD), in situ FT-IR and transmission electron microscopy (TEM). A mechanism has been proposed that Cu2O component involved the reaction course and acted as the active center for nitrate-to-nitrite conversion. The spilt-over hydrogen on Pd is suggested to reduce the adjacent Cu2O into metal Cu, and on the latter the conversion of NO3− to NO2− occurs. However, in strongly acidic solution, copper is dissolved from the Pd-Cu/TiO2 catalyst and released into the solution in the form of copper (Ⅱ) ions, so the reduction of Cu2O to Cu is inhibited and the nitrate reduction cannot be accomplished.

Titania supported palladium-copper bimetallic catalysts (Pd-Cu/TiO2) are prepared by liquid-phase chemical reduction method and then applied in the catalytic reduction of nitrite ions in drinking water. The nitrite conversion and selectivity to N2 influenced by metal molar ratio (Pd:Cu), H2 flow rate, CO2 flow rate, pH value of solution and reaction temperature are also discussed in detail with physical characterizations methods such as XPS, XRD, in situ FT-IR. It is discovered that bimetallic Pd-Cu/TiO2 catalyst has higher activity than monometallic Pd/TiO2 catalyst in the catalytic reduction of nitrite ions and a mechanism is proposed to explain this promoting effect of bimetallic catalyst in this paper.