Design And Catalytic Performance Of The Efficient Composite Photocatalytic Materials

A series high performance photocatalytic composits were prepared and well-characterized, and their catalytic activities were studied. Based on the characteristic of prepared nanocomposits, it was systemically discussed that the crystalline phase and surface morphology of the composites were affected by different synthesized methods. Moreover, the photocatalytic activities of as-prepared composites were studies under different light irradiation.New and efficient heterogeneous photocatalytic material, H₃PW₁₂O₄₀/TiO₂ with anatase crystalline phase, dual-pore structures (micro- and meso-porosity), and nanometer sizes (average particle size of 6 nm) was prepared by combination of the methods of sol-gel and hydrothermal treatment at a lower temperature (200°C, 2°C/min). Composition, structure, physicochemical properties, and surface morphology of the composite were characterized by inductively coupled plasma atomic emission spectrum (ICP-AES), X-ray diffraction (XRD) patterns, UV diffuse reflectance spectroscopy (UV/DRS), ³¹P magic-angle spinning (MAS) NMR, Raman scattering spectra, nitrogen adsorption/desorption determination, and transmission electron microscopy (TEM), respectively. It indicated that the primary Keggin structure remained intact after immobilization of the unit into the TiO₂ network, and hydrogen bonding and chemical interactions between the unit and the anatase network existed in the composite. The composite exhibited visible-light photocatalytic activity to degradation of an aqueous organophosphorus pesticide, parathion-methyl. The high photoactivity of as-prepared nanocomposite could be attributed the higher surface, dual-pore structures, and the synergistic effect existed between the H₃PW₁₂O₄₀ and the TiO₂ matrix. In addition, photodegradation of malachite green (MG) as the model molecular by microwave discharge electrodeless lamps (MDELs) was studied. The effects of different parameters in degradation of MG were discussed, including the MDEL shape, the microwave power, the initial solution concentration and the catalyst dosage. MG was degraded completely within 30 min by U-MDEL when microwave power was 600 W. Additionally, the photodegradation of congo red, acid black, acid fuchsine and salicylic acid had been investigated under the optimum reaction condition of the microwave-enhanced photocatalysis by the use of the composite H₃PW₁₂O₄₀/TiO₂. Compared with the results of the experiment with only MDEL, the time that complete degradation of four organic contaminants needed significantly reduced. The microwave-enhanced photocatalytic degradation took on a good effect, therefore, the use of microwave-enhanced photocatalysis was promising in treating organic contaminants. The H₆P₂W₁₈O₆₂/TiO₂ (Brij-76) composite was prepared by the combination of nonionic surfactant C₁₈H₃7(OCH₂CH₂)10OH (Brij-76) as the template and a single-step sol-gel-hydrothermal method. As-synthesized composite was characterized by FT-IR, XRD, SEM, EDX, N₂ absorption-desorption and NH₃-TPD. The results showed that the average pore diameter of the composite H₆P₂W₁₈O₆₂/TiO₂ (Brij-76) was ca. 3.3 nm, and that of large surface area was 99.78 m²/g. Additionally, the aggregation of particles was effectively inhibited, and surface acidity increased substantially. The photocatalytic eliminations of monochlorobenzene were used as model reaction to evaluate the mirowave enhanced photocatalytic activity of the composite, which was compared with conventional photocatalytic mode with UV-light and visible light. The results showed that the composite H₆P₂W₁₈O₆₂/TiO₂ (Brij-76) can more effectively degradate monochlorobenzene than anatase TiO₂ and H₆P₂W₁₈O₆₂, and which took on a high catalytic activity under mirowave irradiation.The TiO₂-ZrO₂ mixed oxides were prepared by different synthesis methods about calcined or combination of the methods of sol-gel and hydrothermal treatment and template method. Structures, physicochemical properties, and surface morphology of the as-composites were characterized by XRD, nitrogen absorption-desorption, SEM-EDX and TPD techniques. Moreover, the effects of TiO₂-ZrO₂ with different proportion on the structure and their catalytic activities were researched. The results indicated that as-composites were active to decompose aqueous dyes methylene blue, rhodamine B and salicylic acid, and their photocatalytic activities were higher than TiO₂ and ZrO₂. Thereinto, TiO₂-ZrO₂(P₁₂₃-TPHT) mixed oxides was prepared by a one-step sol-gel-solvothermal method in the presence of a triblock copolymer surfactant,Poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethyleneglycol),P₁₂₃(EO₂₀PO₇₀EO₂₀;EO=CH₂CH₂O; PO=CH₂(CH₃)CHO) as the template, of which the surface area and photocatalytic activity was the best.