Photogenerated carrier transfer mechanism and photocatalysis properties of TiO_2 sensitized by Zn(Ⅱ) phthalocyanine

The Zn(Ⅱ) phthalocyanine sensitized TiO2(ZnPc-TiO2) nanoparticles were prepared by hydrothermal method via impregnation with ZnPc.The as-prepared photocatalysts were characterized by X-ray diffractometry(XRD) and diffuse reflectance spectroscopy(DRS),and the surface photovoltage spectroscopy(SPS) and photocatalytic degradation of rhodamine B(RhB) were studied under illuminating.The experimental results indicate that TiO2 sensitized by ZnPc extends its absorption band into the visible region effectively,and the sensitized TiO2 has higher activity than TiO2(Degussa P-25) under the simulated solar light and the visible light.Based on the DRS and SPS results,the mechanism about the photogenerated carrier transfer between TiO2 and ZnPc is proposed.At a lower ZnPc content(≤0.20 μmol/g),ZnPc monomer acts as the electron donor,which provides the photoinduced electrons to the conduction band of TiO2.These photoinduced electrons can transfer to molecular oxygen(O2),leading to the formation of active species,such as superoxide/hydroxide radicals and singlet oxygen,which is beneficial to the photocatalytic reaction.While at a higher ZnPc content(0.20 μmol/g),the formation of ZnPc dimer results in the decrease of photocatalytic activities of ZnPc-TiO2 photocatalyst.     

Comparative study on photocatalytic properties of TiO2 nanoparticles prepared in acidic medium and basic medium by hydrothermal method

In order to investigate the difference of phtotocatalytic properties of TiO2 samples prepared in different pH conditions,TiO2 nanoparticles were prepared in acidic medium and basic medium by a hydrothermal process,respectively.The samples were characterized using XRD,TEM,BET,XPS,surface photovoltage spectroscopy (SPS) and field-induced surface photovoltage spectroscopy (FISPS).Effects of temperature and pH in the hydrothermal process on particle sizes,specific surface areas,and photocatalytic properties of the TiO2 nanocrystalline were investigated.The experimental results indicate that the photocatalysis activity of TiO2 nanoparticles prepared in basic medium (B-TiO2) is superior to that in acidic medium (A-TiO2),which is ascribed to the difference of surface state between A-TiO2 and B-TiO2.     

Preparation and film-growing mechanism of hydrous zirconia coated on TiO_2

To overcome the photochemical activity of rutile used as a pigment and improve its durability in application, hydrous zirconia-coated TiO2 was prepared by the precipitation method. High-resolution transmission electron microscope (HRTEM) and X-ray photoelectron spectroscopy (XPS) were used to characterize the morphology and surface structure of hydrous zirconia-coated TiO2. The ζ-potential and ultraviolet (UV) absorption of both coated and uncoated rutile were examined. The results show that hydrous zirconi...     

Preparation of TiO2 Thin Film and Its Antibacterial Activity

TiO2 nanometer thin films with photocatalytic antibacterial activity were prepared by the sol-gel method on fused quartz and soda lime glass precoated with a SiO2 layer. The thin films were characterized by X-ray photoelectron spectroscopy ( XPS ), scanning electron microscopy (SEM), and X- ray diffraction ( XRD ). The results show that sodium and calcium diffusion into nascent TiO2 film is effectively retarded by the SiO2 layer precoated on the soda lime glass, The antibacterial activity of the films was determined. The crystalline of TiO2 nanometer thin film has important effects on the antibacterial activity of the film.     

STUDY ON PHOTOCATALYTIC MECHANISM OF SOL-GEL-DERIVED Pb-DOPED TiO_2 THIN FILMS

Pb-doped TiO2 photocatalytic thin films were prepared on a soda-lime glass substrate via sol-gel method using TiO2 sol solution containing lead and characterized by X-ray photoelectron spectroscopy (XPS). The results showed that besides oxides of Ti(IV) there is a certain amount of oxides of To(Ⅲ) and Ti(Ⅱ) and Pb exists in the forms of PbTiO3 and PbO. The photocatalytic activity of the Pb-doped TiO2 films was evaluated by the photocatalytic decolorization of aqueous methyl orange and photocatalytic mechanism mas also analyzed.     

Self-assembly of Ag-TiO2 nanoparticles: Synthesis, characterization and catalytic application

The formation of Ag clusters on titanium oxide (TiO2) nanoparticles was achieved by self-assembly process and calcination. The obtained nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and ultraviolet visible spectroscopy (UV-Vis), and conventional techniques (XRD, TEM and UV-Vis) were used to identify Ag particles on the TiO2 surfaces. The results show that Ag-TiO2 particles can be applied to improve catalytic activity of the epoxidation of styrene oxides. Styrene oxide is the main product of catalytic reaction with H2O2 as the oxidant by using Ag-TiO2 nanoparticles as catalysts. High catalytic activitity of styrene oxide can be obtainable at 80 ℃. The reaction temperature, reaction time, the molar ratio of H2O2/styrene and solvent affect greatly the catalytic epoxidation of styrene.     

Composite semiconductor quantum dots CdSe/CdS Co-sensitized TiO2 nanorod array solar cells

CdSe/CdS semiconductor quantum dots co-sensitized TiO2 nanorod array was fabricated on the transparent conductive fluorine-doped tin oxide (FTO) substrate using the hydrothermal and successive ionic layer adsorption and reaction (SILAR) process. The structural and morphological properties of the samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The results indicate that CdSe/CdS QDs are uniformly coated on the surface of the TiO2 nanorods. The shift of light absorption edge was monitored by taking UV-visible absorption spectra. Compared with the absorption spectra of the TiO2 nanorod array, deposition of CdSe/CdS QDs shifts the absorption edge to the higher wavelength. The enhanced light absorption in the visible-light region of CdSe/CdS/TiO2 nanorod array indicates that CdSe/CdS layers can act as co-sensitizers in quantum dots sensitized solar cells (QDSSCs). By optimizing the CdSe layer deposition cycles, a photocurrent of 5.78 mA/cm2, an open circuit photovoltage of 0.469 V and a conversion efficiency of 1.34 % were obtained under an illumination of 100 mw/cm2.     

The synthesis, characterization, photocatalytic evaluation and deactivation behavior of sheet-like nano titania

The sheet-like nano TiO2 particles were prepared by using hydrothermal method, and were characterized by X-ray diffraction(XRD), infrared spectroscopy(IR), and transmission electron microscopy (TEM). It is found that the nanoparticle sizes and crystallinity increase with the increase of hydrothermal temperature from 150 ℃ to 160 ℃, and then to 180 ℃. With the increase of particle sizes, the absorption capacities and photocatalytic abilities of as-prepared TiO2 particles for crystal violet become better and better. The nano TiO2 with big particles is more stable than that with small particles, although its initial photocatalytic activity is relatively lower compared with that of the small particle samples.     

Grain Size and Photocatalytic Activity of Nanometer TiO_2 Thin FilmsPrepared by the Sol-gel Method

Transparent anatase TiO2 nanometer thin films with photocatalytic activity were prepared via the sol-gel method on soda-lime glass. The thickness , crystalline phase, grain size, surface hydroxyl amount and so on were characterized by scanning electron microscopy (SEM) , X-ray diffraction (XRD), transmission electron microscopy ( TEM), X-ray photoelectron spectroscopy (XPS) and UV-visible spectrophotometer ( UV-VIS). The photocatalytic activity of TiO2 thin films was evaluated for the photocatalytic decolorization of aqueous methyl orange . The effects of film thickness on the crystalline phase, grain size, transmittance and photocatalytic activity of nanometer Ti02 thin films were discussed.     

Enhanced photocatalytic activity of (La, N) co-doped TiO_2 by TiCl_4 sol-gel autoigniting synthesis

(La, N) co-doped TiO2 photocatalysts were synthesized using TiCl4 sol-gel autoigniting synthesis (SAS) starting from a complex compound system of TiCl4-La(NO3)3-citric acid-NH4NO3-NH3?H2O, in which the (La, N) co-doped process was accom- plished in the formation of TiO2 nanocrystals. The prepared samples were characterized by using X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS) and UV-vis diffuse reflectance spectra. The results indicated that nitrogen and lanthanum were incorporated into the lattice and interstices of titania nanocrystals, which resulted in narrowing the band gap and promoting the sepa- ration of photoexcited hole-electron pairs, respectively, and showing expected red-shifts and enhanced photocatalytic activity under visible light. The mechanism on nitrogen doping and enhancement in photocatalytic activity of (La, N) co-doped titania by SAS was discussed in detail.     

Fabrication and Photocatalytic Activity of Ag_3PO_4-TiO_2 Heterostructural Nanotube Arrays

To extend the absorption capability of TiO_2 into visible light region and inhibit the recombination of photogenerated electrons and holes,we put forward an effective strategy of the coupling of TiO_2 with a suitable semiconductor that possesses a narrow band gap.Meanwhile,Ag_3PO_4-TiO_2 heterostructuralnanotube arrays were prepared by the two-step anodic oxidation to obtain the TiO_2 nanotube arrays and then by a deposition-precipitation method to load Ag_3PO_4.The samples were characterized by field emission scanning electron microscopy(FESEM),energy dispersive spectrometry(EDS),X-ray diffraction(XRD),and UV-vis diffuse reflectance spectroscopy(UV-vis DRS).The experimentalresults showed that Ag_3PO_4 nanoparticles were uniformly dispersed on the highly ordered TiO_2 nanotube arrays,which increased the visible-light absorption of TiO_2 photocatalyst.The photocurrent density and photocatalytic degradation of methylorange indicated that the performance of Ag_3PO_4-TiO_2 heterostructuralnanotube arrays was better than that of the TiO_2 nanotube arrays,which could be attributed to the effective electron-hole separation and the improved utilization of visible light.     

铈掺杂改性TiO2的光催化性能

采用溶胶一凝胶法制备稀土金属铈（Ce）掺杂改性纳米TiO2光催化剂。运用X-射线衍射（XRD）、紫外一可见漫反射光谱（DRS）、程序升温氧吸附一脱附、透射电镜（TEM）等手段表征催化剂的组成、结构特征及与光催化性能的关联;以催化剂上甲基橙的紫外光催化降解反应为探针,探讨了掺杂前后TiO2光催化剂在紫外光下的活性规律。研究结果表明Ce的掺杂有利于抑制TiO2晶粒生长和晶型的转变,提高晶体的热稳定性,提高TiO2催化剂的可见光吸收能力;由于Ce具有贮存氧的能力,有助于TiO2催化剂对氧气的吸附,其吸附量随Ce掺杂量的增加而增加。     

金属酞菁敏化二氧化钛可见光催化降解染料废水的研究

研究了染料敏化半导体光催化剂-酞菁镁/TiO_2复合粒子在可见光波段的光催化性能.通过溶胶-凝胶的方法制得TiO_2胶体再进行焙烧,得到二氧化钛粉末和薄膜,再用酞菁镁敏化,制得酞菁镁/TiO_2复合粒子.利用X射线衍射、扫描电子显微镜、红外光谱和X光电子能谱分析等方法对TiO_2和酞菁镁/TiO_2复合粒子的物理性质进行了表征;并以亚甲基蓝作为目标物研究其光催化性能.结果表明,酞菁镁可以敏化二氧化钛,使其吸收波长红移,并具有较好的光催化性能.     

Fabrication of BiVO_4:Effect of Structure and Morphology on Photocatalytic Activity and Its Methylene Blue Decomposition Mechanism

BiVO_4 photocatalysts were synthesized by a surfactant free hydrothermal method without any further treatments,and characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),ultraviolet-visible diffuse reflectance spectroscopy(UV-vis DRS),Raman spectroscopy,and Brunauer-Emmett-Teller(BET) surface area techniques.The photocatalytic activity was evaluated for the degradation of the methylene blue(MB) under visible light irradiation.Seen from the structural and morphological characterization,it is stated that the obtained samples present monoclinic phase,and the pH value has significant influence on the morphologies.The enhanced photocatalytic performance was associated with its crystallinity,unique morphology,band gap energy,BET specific surface area,surface charge and adsorption capacity.The recycle experiments results show that the BiVO_4 photocatalysts have excellent photo-stability,and we deduced a possible mechanism by examining the effects of the active species involved in the photocatalytic process for MB photocatalytic degradation.     

Comparative study on photocatalytic properties of TiO_2 nanoparticles prepared in acidic medium and basic medium by hydrothermal method

In order to investigate the difference of phtotocatalytic propenties of TiO_2 samples prepared in different pH conditions, TiO_2 nanoparticles were prepared in acidic medium and basic medium by a hydrothermal process,respectively.The samples were characterized using XRD,TEM, BET,XPS,surface photovoltage spectroscopy(SPS)and field-induced surface photovoltage spectroscopy(FISPS).Effects of temperature and pH in the hydrothermal process on particle sizes,specific surface areas,and photocatalytic properties of the TiO_2 nanocrystalline were investigated.The experimental results indicate that the photocatalysis activity of TiO_2 nanoparticles prepared in basic medium (B-TiO_2) is superior to that in acidic medium (A-TiO_2),which is ascribed to the difference of surface state between A-TiO_2 and B-TiO_2.     

掺杂金属卟啉的TiO_2薄膜对活性艳红X-3B染料的光催化降解性能

采用溶胶凝胶的方法,将具有高光敏性的四(对羟基)苯基锌卟啉(ZnTHPP,下简称锌卟啉)在钛酸丁酯[Ti(OBu)4]水解的条件下均匀嵌入到了TiO2无机网络中,又采用旋涂法制备了ZnTHPP/TiO2复合薄膜。利用UV Vis吸收光谱对薄膜的紫外可见光吸收性质进行了研究,结果表明锌卟啉的加入能有效的拓宽TiO2的可见光吸收范围。通过光催化降解活性艳红X 3B染料实验,对所制备的ZnTHPP/TiO2复合薄膜的光催化活性进行了考察,研究发现以ZnTHPP/TiO2作为光催化剂对活性艳红X 3B染料能有效的降解,表现出了较好的可见光催化活性。     

Fabrication of BiVO<Subscript>4</Subscript>: Effect of structure and morphology on photocatalytic activity and its methylene blue decomposition mechanism

BiVO₄ photocatalysts were synthesized by a surfactant free hydrothermal method without any further treatments, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), Raman spectroscopy, and Brunauer-Emmett-Teller (BET) surface area techniques. The photocatalytic activity was evaluated for the degradation of the methylene blue (MB) under visible light irradiation. Seen from the structural and morphological characterization, it is stated that the obtained samples present monoclinic phase, and the pH value has significant influence on the morphologies. The enhanced photocatalytic performance was associated with its crystallinity, unique morphology, band gap energy, BET specific surface area, surface charge and adsorption capacity. The recycle experiments results show that the BiVO₄ photocatalysts have excellent photo-stability, and we deduced a possible mechanism by examining the effects of the active species involved in the photocatalytic process for MB photocatalytic degradation.     

Highly Efficient Removal of Organic Dyes by Novel As-synthesized AgBr/montmorillonite Composite

A facile deposition method has been developed for large-scale synthesis of visible-light-driven AgBr/montmorillonite composite catalyst for the first time. The as-synthesized samples were characterized by X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS), Fourier transform infrared spectroscopy(FT-IR), transmission electron microscopy(TEM), UV-vis diffuse reflectance spectroscopy(UV-vis DRS) and Brunauer-Emmett-Teller(BET) surface area analysis, respectively. Through the combined action of adsorption and photodegradation, the as-prepared AgBr/montmorillonite composite exhibited a higher removal efficiency for rhodamine B(RhB) than that of Na-montmorillonite and AgBr. For the methyl orange(MO) removal, the AgBr/montmorillonite composite possessed a superior photocatalytic performance compared with Namontmorillonite and AgBr. The enhanced photocatalytic activity of AgBr/montmorillonite composite can be attributed to the effective separation of the electron-hole pairs. In AgBr/montmorillonite suspension, the superoxide radicals are the main reactive oxygen species for dye degradation under visible light illumination.     

Highly Efficient Synthesis of Environmentally Friendly Ag-modified TiO_2 Nanoflowers to Enhance Photocatalytic Performance

Ag-modified TiO_2 nanoflowers were prepared using a two-step process. The experimental process is green and free from contamination and can be synthesized directly at room temperature. Compared with pure TiO_2, Ag-modified TiO_2 enhances the absorption of visible light and effectively promotes the detachment of photoelectron pairs, Ag-TiO_2 has a significantly enhanced visible light response activity to photodecomposition of methyl orange(MO). It is shown that the strong interaction between Ag nanoparticles and TiO_2 enhances the photocatalytic activity of TiO_2 nanoflowers. The self-made open-air reactor was used to test the photocatalytic performance of different samples. The results showed that Ag-modified TiO_2 nanoflowers had excellent photodegradation ability. After repeated photodegradation of MO, Ag-modified TiO_2 nanoflowers showed good stability.     

Novel Visible Light Driven Magnetically Separable Graphene/BiOBr Composite Photocatalysts with Enhanced Photocatalytic Activity

Novel visible light magnetically separable graphene-based BiOBr composite photocatalysts were prepared for the first time. The structures, morphologies and optical properties were characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction and ultravioletvisible spectroscopy, respectively. The photocatalytic activity of the resulting samples was evaluated by degradation of tetracycline under visible light irradiation. An appropriate amount of introduced graphene can significantly enhance the photocatalytic activities. The enhanced activities were mainly attributed to the enhanced light absorption and the interfacial transfer of electrons. The corresponding photocatalytic mechanism was proposed based on the results.