The samples of nano-size ZnO were pre pared by precipitation,hydrolysis,sol-gel method and characterized b y X-ray diffraction,Uv-Vis diffuse r eflection spectrum,and time resolv ed luminescent spectrum.The results sh...The samples of nano-size ZnO were pre pared by precipitation,hydrolysis,sol-gel method and characterized b y X-ray diffraction,Uv-Vis diffuse r eflection spectrum,and time resolv ed luminescent spectrum.The results showed that the crystallite dimensions of a ll ZnO samples were coarsening with i ncreasing annealing temperature an d the grain sizes prepared by sol-gel meth od were obviously smaller than the others prepared by precipitation and h y-drolysis method.Under excitation o f monochromatic light of wavelength300nm,a strong and broad photolumin es-cence(PL)emissions were observed in the wavelength range of 420～780nm.As the grain size decreased,the PL peak positions moved to shorter wavelengths.And as the annealing temperature increased,the peak intensity de-creased.The photoluminescence dec ay profile of ZnO was well described b y three decay components of 46ns,330ns and 1630ns.展开更多
The Gd3+-doped TiO2 photocatalyst was prepared by the sol-gel and impregnation method. The effect of Gd3+ doping on crystalline size, BET surface area and photocatalytic activity was studied by XRD, FTIR, BET, UV-Vis ...The Gd3+-doped TiO2 photocatalyst was prepared by the sol-gel and impregnation method. The effect of Gd3+ doping on crystalline size, BET surface area and photocatalytic activity was studied by XRD, FTIR, BET, UV-Vis diffuse reflection spectroscopy, surface photovoltage spectroscopy (SPS). The activities of TiO2 and Gd3+-doped TiO2 catalysts for photocatalytic degradation of ethylene were studied by means of in situ FTIR. The photocatalytic reaction rate constant of ethylene becomes larger through Gd3+ doping. The rate constant of TiO2 was k1=8.51×10-4 min-1, while that of Gd/TiO2 was k2=1.85×10-3 min-1. At the same time, the yield of CO2 increased with Gd3+ doping. The enhancement in photocatalytic activity is probably due to the increase of light absorption, higher content of anatase, smaller crystal line size and higher specific surface area. In addition, the higher photocatalytic activity of Gd3+-doped TiO2 might be attributed to the effective separation of photo-generated electron-hole pairs.展开更多
Pt/Pt 4+-TiO2 photocatalyst prepared by a modified sol-gel process was investigated by X-ray diffraction, UV-Vis diffuse reflectance spectra, X-ray photoelectron spectroscopy, time-resolved photoconductivity and terep...Pt/Pt 4+-TiO2 photocatalyst prepared by a modified sol-gel process was investigated by X-ray diffraction, UV-Vis diffuse reflectance spectra, X-ray photoelectron spectroscopy, time-resolved photoconductivity and terephthalic acid fluorescence probing. The photocatalytic activities of catalysts were evaluated by using ethylene oxidation studies under visible light irradiation（λ>450 nm） from 40 to 62 ℃. It is found that the platinum doping in titania caused significant absorption shift to the visible region and the surface recombination of photogenerated carriers was inhibited. The results show that ethylene was not converted on conventional TiO2 while the conversion was 90% and the complete mineralization was achieved over Pt-Pt 4+/TiO2 at 62 ℃ in our experiment. Besides the exponential increase of thermalcatalytic activity, pure photocatalytic activity of the planitized sample enhanced linearly with the increase of temperature.展开更多
TiO2 membranes were prepared on aluminum-alloy thin plates by electrophoretic deposition and dip coating in a colloid solution of TiO2, respectively. The photocatalytic activity of TiO2 membrane was compared using eth...TiO2 membranes were prepared on aluminum-alloy thin plates by electrophoretic deposition and dip coating in a colloid solution of TiO2, respectively. The photocatalytic activity of TiO2 membrane was compared using ethylene as reactant, and the crystal and morphological structure of the membrane were characterized by XRD and SEM. The results showed that a more compact membrane with high loading of TiO2 but lower photocatalytic activity of unit TiO2 mass was obtained by electrophoresis compared with dip coating method. The addition of polyethylene glycol (PEG) to the sol of TiO2 could improve the specific photocatalytic activity (ethylene conversion per unit mass TiO2 and unit area of membrane piece) of the electrophoresis-membrane prepared from the sol, but could not change the specific photocatalytic activity of the dip-coating membrane from the sol. The ethylene conversion on the electrophoresis membrane prepared from the sol containing PEG (50 g·L-1) was 9 times of that on the dip coating membrane. The effect of PEG on the properties of electrophoresis-membrane of TiO2 was attributed to the change of electrokinetic properties of sol. Addition of PEG decreased of colloid particles and the electroosmosis velocity of diffuse layer of colloid particles. These favored the formation of a low compact and porous membrane on the electrode in electric field, and thus increasing the availability of TiO2 in photocatalytic process.展开更多
文摘The samples of nano-size ZnO were pre pared by precipitation,hydrolysis,sol-gel method and characterized b y X-ray diffraction,Uv-Vis diffuse r eflection spectrum,and time resolv ed luminescent spectrum.The results showed that the crystallite dimensions of a ll ZnO samples were coarsening with i ncreasing annealing temperature an d the grain sizes prepared by sol-gel meth od were obviously smaller than the others prepared by precipitation and h y-drolysis method.Under excitation o f monochromatic light of wavelength300nm,a strong and broad photolumin es-cence(PL)emissions were observed in the wavelength range of 420～780nm.As the grain size decreased,the PL peak positions moved to shorter wavelengths.And as the annealing temperature increased,the peak intensity de-creased.The photoluminescence dec ay profile of ZnO was well described b y three decay components of 46ns,330ns and 1630ns.
文摘The Gd3+-doped TiO2 photocatalyst was prepared by the sol-gel and impregnation method. The effect of Gd3+ doping on crystalline size, BET surface area and photocatalytic activity was studied by XRD, FTIR, BET, UV-Vis diffuse reflection spectroscopy, surface photovoltage spectroscopy (SPS). The activities of TiO2 and Gd3+-doped TiO2 catalysts for photocatalytic degradation of ethylene were studied by means of in situ FTIR. The photocatalytic reaction rate constant of ethylene becomes larger through Gd3+ doping. The rate constant of TiO2 was k1=8.51×10-4 min-1, while that of Gd/TiO2 was k2=1.85×10-3 min-1. At the same time, the yield of CO2 increased with Gd3+ doping. The enhancement in photocatalytic activity is probably due to the increase of light absorption, higher content of anatase, smaller crystal line size and higher specific surface area. In addition, the higher photocatalytic activity of Gd3+-doped TiO2 might be attributed to the effective separation of photo-generated electron-hole pairs.
文摘Pt/Pt 4+-TiO2 photocatalyst prepared by a modified sol-gel process was investigated by X-ray diffraction, UV-Vis diffuse reflectance spectra, X-ray photoelectron spectroscopy, time-resolved photoconductivity and terephthalic acid fluorescence probing. The photocatalytic activities of catalysts were evaluated by using ethylene oxidation studies under visible light irradiation（λ>450 nm） from 40 to 62 ℃. It is found that the platinum doping in titania caused significant absorption shift to the visible region and the surface recombination of photogenerated carriers was inhibited. The results show that ethylene was not converted on conventional TiO2 while the conversion was 90% and the complete mineralization was achieved over Pt-Pt 4+/TiO2 at 62 ℃ in our experiment. Besides the exponential increase of thermalcatalytic activity, pure photocatalytic activity of the planitized sample enhanced linearly with the increase of temperature.
文摘TiO2 membranes were prepared on aluminum-alloy thin plates by electrophoretic deposition and dip coating in a colloid solution of TiO2, respectively. The photocatalytic activity of TiO2 membrane was compared using ethylene as reactant, and the crystal and morphological structure of the membrane were characterized by XRD and SEM. The results showed that a more compact membrane with high loading of TiO2 but lower photocatalytic activity of unit TiO2 mass was obtained by electrophoresis compared with dip coating method. The addition of polyethylene glycol (PEG) to the sol of TiO2 could improve the specific photocatalytic activity (ethylene conversion per unit mass TiO2 and unit area of membrane piece) of the electrophoresis-membrane prepared from the sol, but could not change the specific photocatalytic activity of the dip-coating membrane from the sol. The ethylene conversion on the electrophoresis membrane prepared from the sol containing PEG (50 g·L-1) was 9 times of that on the dip coating membrane. The effect of PEG on the properties of electrophoresis-membrane of TiO2 was attributed to the change of electrokinetic properties of sol. Addition of PEG decreased of colloid particles and the electroosmosis velocity of diffuse layer of colloid particles. These favored the formation of a low compact and porous membrane on the electrode in electric field, and thus increasing the availability of TiO2 in photocatalytic process.
