Mechanochemical preparation of sulfur-doped nanosized TiO2 and its photocatalytic activity under visible light

In order to make nanosized TiO2 photocatalyst responsive to visible light and effectively utilize solar energy, we have, for the first time, prepared S-doped nanosized TiO2 by a mechanochemical method with hydrolysis of TiCl4. The as-prepared S-doped nanosized TiO2 possesses strong absorption for visible light of 400-650 nm and shows high photocatalytic activity for decomposition of methylene blue under irradiation of visible light. The oxidation states of the S atoms incorporated into TiO2 were determined to be S^6＋ and S^4＋. The comparative study of fluorescence emission spectra shows that S-doping has also improved the separation of electron-hole pairs.     

Preparation, characterization and photodegradation of methylene blue based on TiO2 microparticles modified with thiophene substituents

The new microparticles,2-formylthiophene(FT)/TiO2 and(E)-1,2-bis(5-formyl-2-thienyl) ethylene(EBFTE)/TiO2 were synthesized with a silane coupling agent.The prepared TiO2 composites were characterized using Ultraviolet-Vis absorption(UV-Vis),X-ray diffraction(XRD),scanning electron microscope(SEM) and thermogravimetric analyzer(TGA).Methylene blue was used as a model material to examine the photocatalytic activities of the prepared catalysts under both Ultraviolet-Vis(UV) and visible(Vis) light.The enhanced photocatalytic activities were observed in the presence of(FT)/TiO2 and EBFTE/TiO2 under Vis light.It suggests that FT or EBFTE plays a block or active role in the photodegradation mechanisms under UV and Vis light irradiation,respectively.     

Catalysis of organic pollutant photodegradation by metal phthalocyanines immobilized on TiO<Subscript>2</Subscript>@SiO<Subscript>2</Subscript>

A TiO2@SiO2 hybrid support was prepared by the sol-precipitation method using n-octylamine as a template.The photocatalyst manganese phthalocyanine tetrasulfonic acid (MnPcS) was immobilized on the support to form MnPcS-TiO2@SiO2.X-ray diffraction (XRD) and UV-Visible diffuse reflectance spectra (UV-Vis DRS) were employed to characterize the catalyst.The photocatalytic degradation of rhodamine B (RhB) and the catalytic oxidation of o-phenylenediamine (OPDA) under visible light irradiation were used as probe reactions.The mineralization efficiency and the degradation mechanism were evaluated using chemical oxygen demand (COD Cr) assays and electron spin resonance (ESR),respectively.RhB was efficiently degraded by immobilized MnPcS-TiO2@SiO2 under visible light irradiation.Complete decolorization of RhB occurred after 240 min of irradiation and 64.02% COD Cr removal occurred after 24 h of irradiation.ESR results indicated that the oxidation process was dominated by the hydroxyl radical (·OH) and superoxide radical (O-·2) generated in the system.     

Synthesis of PbS–K2La2Ti3O10 composite and its photocatalytic activity for hydrogen production

Photocatalyst, lead sulfide (PbS )-intercalated layer perovskite-type compound (K2La2Ti3O10), was synthesized via ion-exchange reaction, butylamine pillaring and sulfuration processes under the assistance of the microwave irradiation. The structure of the photoc atalysts was determined by means of powder X-ray diffraction, scanning electron microscope, ultraviolet- visible diffuse reflection spectra and photoluminescence measu rement. And the photocatalytic activity of the composite compound for hydrogen production was also investigated. The experimental results showed that the intercalation of PbS in the layered space of K2La2Ti3O10 greatly improved the absorption edge and the photocatalytic activity. Hydrogen production of the PbS–K2La2Ti3O10 was 127.19 mmol/(g cat) after 3 h irradiation of ultraviolet light.     

Preparation,Characterization and Solar Photocatalytic Activity of P-YFeO_3-N-TiO_2 Nanojunctions

1 Results YFeO3-TiO2 composite photocatalysts with p-n heterojunction have been prepared by physical amalgamation.The physical and photophysical properties of the composites were characterized by XRD,TEM,UV-vis/DRS,XPS.Effects of calcination temperature and constitute content on structure and surface characterization were also investigated.Results show that the presence of p-n junction not only has visible light harvesting but potential force for hole-electron pair separation.A preliminary investigation of photocatalytic activity on orange II showed that YFeO3-TiO2 heterojunctions could be activated under visible light irradiation.The optimum photocatalytic junction is w(TiO2) =90% in the composites after calcining at 600 ℃.The improved photocatalytic activity,comparing with that of pure TiO2 and pure YFeO3,might attribute to the p-n heterojunction composed of p-type YFeO3 and n-type TiO2.Study of the process of electron and hole migratation will facilitate the exploitation of novel,highly efficient,visible-light-driven photocatalyst.     

Comparison of the effect of hydrogen incorporation and oxygen vacancies on the properties of anatase TiO2: electronics,optical absorption,and interaction with water

Hydrogenation has been recently developed as an approach to improve the visible-light response of titanium dioxide （TiO2）; however, the effect of hydrogenation on the electronics and optical absorption of anatase TiO2 has been widely debated. In this work, the electronic structures and optical properties of hydrogenated TiO2 and its interaction with water have been studied using the density functional theory plus Hubbard model. A comparison of the effect of hydrogenation and introduction of oxygen vacancies （OVs） to TiO2 is presented. It is found that both hydrogenation and OVs can promote the absorption of visible light and strengthen the adsorption of water. Compared with OVs, hydrogen incorporation can lead to local distortion and even amorphous structures when it is heavily doped.     

Preparation of graphene and TiO2 layer by layer composite with highly photocatalytic efficiency

A process for fabricating graphene and TiO2 layer by layer composite was introduced to improve the photocatalytic activity by controlling the layers, thickness and the mass ratio between graphene and TiO2. The graphene oxide (GO) was synthesized from natural graphite pow der by the modified Hummers met hod. Large-area uniform GO and TiO2 thin films were made by a spin-coating process in turn. After exposure of the TiO2/GO multilayer film to UV light irradiation which allows the reduction of GO to graphene, a novel photocatalyt ic structure as graphene and TiO2 layer by layer composite was synthesized. The cross-sectional SEM image showed that a clear layer by layer microstructure with a single layer thickness of graphene or TiO2 was in the range of about 50 nm. The total thickness of the film was around 5 μm which was varied according to the layer number of spin coating process. Raman spectra revealed th at significant structural changes occurred through UV light irradiation. Photodegrada tion for methylene blue (MB) exhibited that the layer by layer com posite is of higher photocatalytic activity than the pure TiO2 layer.     

Fluorescence and sensitization performance of phenylene-vinylene-substituted polythiophene

A new kind of polythiophene derivative, Poly(3-{2-[4-(2-ethylhexyloxy)-phenyl]-vinyl}-2,2′-bithiophene) (PTh), was applied in dye-sensitized solar cell to extend the light response of nanocrystalline TiO2 electrode. UV-vis absorption and fluorescence spectra were employed to investigate the interaction of PTh with nanocrystalline TiO2. The absorption coefficient of the PTh was high in visible part of spec- trum, and the fluorescence emission of the PTh can be efficiently quenched by TiO2 nanoparticles ow- i...     

Preconcentration and Separation of Trace Copper in Water Samples with Nanometer-Size TiO2 Colloid and Determination by FAAS

A new absorbent of nanometer-size TiO2 colloid for Cu(Ⅱ) was studied in this work. The adsorption rate could reach above 99% when the pH values were at the range of 5-6. The adsorption balance time, adsorption capacities, and the eluent were investigated. A novel method of trace Cu(Ⅱ) preconcentration and separation with nanometer-size titanium dioxide colloid and determination by flame atomic absorption spectrometry (FAAS) was advanced. The detection limit (3σ) of the method was 1.15 μg· L~(-1) , and the relative standard deviation (R.S.D) was 1.53% (n=6). Environmental sample experiments were also conducted to test the feasibility of the method, and it came out that the recovery rates were between 95.9% and 97.8%.     

Flexible dye-sensitized solar cell based on PCBM/P3HT heterojunction

Using blend heterojunction consisting of C60 derivatives [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and poly(3-hexylthiophene) (P3HT) as charge carrier transferring medium to replace I3–/I– redox electrolyte,a novel flexible dye-sensitized solar cell (DSSC) is fabricated.The characterization of infrared spectra and ultraviolet-visible spectra shows that the PCBM/P3HT heterojunction has not only the absorption in ultraviolet light for PCBM,but also the absorption in visible and near infrared light for P3HT,which widens the photoelectric response range for DSSC.The influence of PCBM/P3HT mass ratio on the performance of the solar cell is discussed.Under 100 mW cm–2 (AM 1.5) simulated solar irradiation,the flexible solar cell achieves a lightto-electric energy conversion efficiency of 1.43%,open circuit voltage of 0.87 V,short circuit current density of 3.0 mA cm–2 and fill factor of 0.54.     

铕掺杂TiO2粉末的制备及其可见光光催化性能研究

以钛酸四正丁酯为原料,采用水热法制备铕掺杂TiO2粉末,对铕掺杂TiO2粉末的可见光光催化性能进行研究,并通过XRD、SEM分析对其进行表征。结果表明,铕掺杂TiO2粉末没有改变晶相结构,铕掺杂后使TiO2粉末由不规则形状转变为实心球状,且提高了TiO2粉末的光催化性能。模拟太阳光实验发现,铕掺杂TiO2粉末可明显提高其可见光光催化的降解能力,当辐照度为500W/m2、时间为240min时,其降解率达到78%。     

二氧化钛-硫化镉/还原氧化石墨烯复合材料光催化降解废水中有机物的研究

采用溶剂热法制备出二氧化钛-硫化镉/还原氧化石墨烯(TiO_2-CdS/rGO)三元复合光催化材料,研究其对亚甲基蓝、罗丹明B的光催化降解效果.结果表明,TiO_2-CdS/rGO对亚甲基蓝、罗丹明B的光催化降解效果优于TiO_2-CdS的,催化效率得到明显提高,降解时间大大缩短.在可见光照射下,以TiO_2-CdS/rGO为光催化剂,当光反应时间为40min时,亚甲基蓝、罗丹明B的降解率可达100%.     

二氧化钛-硫化镉/氧化石墨烯复合材料光催化降解废水中有机物的研究

本论文采用溶剂热法制备出TiO₂-CdS/rGO三元复合光催化材料,并对其降解亚甲基蓝、罗丹明B的光催化活性进行研究,发现TiO₂-CdS/rGO对于亚甲基蓝、罗丹明B的光催化降解活性优于TiO₂-CdS,催化效率明显提高,降解时间大大缩短;在可见光照射下,以TiO₂-CdS/rGO为光催化剂,光反应时间40 min,亚甲基蓝、罗丹明B的降解率可达100%。本文还研究了催化材料的稳定性、催化剂用量对光催化降解效果的影响。     

Synthesis of Cu–TiO2/CuS p-n heterojunction via in situ sulfidation for highly efficient photocatalytic NO removal

Cu doped TiO₂/CuS (Cu–TiO₂/CuS) p-n heterojunction was synthesized via in situ sulfidation method for efficient photocatalytic removal of NO at ppb-level. The results show that optimized Cu–TiO₂/CuS heterojunction possessed a maximum efficiency of 85% for the removal of NO under visible light irradiation, which was approximately 8.5, 4.3 and 1.2 times that of CuS, TiO₂ and Cu–TiO₂, respectively. The improved photocatalytic performance is attributed to the enhancement of visible light absorption and charge carrier separation induced by the construction of p-n heterojunction. Meanwhile, the p-n heterojunction charge transfer mechanism of Cu–TiO₂/CuS was verified by systematic investigations. The appropriate band structures of the two components and the internal electric field formed at the interface of the heterojunction were two factors for this charge transfer mechanism. Furthermore, the role of active species in NO removal was explored, and the corresponding mechanism for NO removal of the heterojunction was proposed. This work provides a promising approach for the synthesis of heterojunction photocatalysts and facilitates the application of photocatalysts in sustainable and efficient pollutant removal.     

银掺杂多孔氧化钛光催化甲基橙降解反应条件的探究

利用溶胶-凝胶法结合光还原法制备Ag掺杂多孔TiO_2光催化剂,以甲基橙的降解效果为评价标准,考查了光照降解时间、光催化剂用量、甲基橙溶液初始浓度、溶液pH值对光催化剂催化降解甲基橙的影响。结果表明,本方法制备的光催化剂无论是在紫外光还是可见光下均具有优良的光催化性能:在浓度为10 mg/L的甲基橙溶液中,4 g/L光催化剂,紫外光照射80 min,甲基橙可实现100%完全降解;相同催化条件下,可见光照100 min,甲基橙完全降解;当反应溶液pH=2时,紫外光和可见光都可在20 min内实现甲基橙的完全降解。     

Preparation of graphene and TiO2 layer by layer composite with highly photocatalytic efficiency

A process for fabricating graphene and TiO₂ layer by layer composite was introduced to improve the photocatalytic activity by controlling the layers, thickness and the mass ratio between graphene and TiO₂. The graphene oxide (GO) was synthesized from natural graphite powder by the modified Hummers method. Large-area uniform GO and TiO₂ thin films were made by a spin-coating process in turn. After exposure of the TiO₂/GO multilayer film to UV light irradiation which allows the reduction of GO to graphene, a novel photocatalytic structure as graphene and TiO₂ layer by layer composite was synthesized. The cross-sectional SEM image showed that a clear layer by layer microstructure with a single layer thickness of graphene or TiO₂ was in the range of about 50 nm. The total thickness of the film was around 5 μm which was varied according to the layer number of spin coating process. Raman spectra revealed that significant structural changes occurred through UV light irradiation. Photodegradation for methylene blue (MB) exhibited that the layer by layer composite is of higher photocatalytic activity than the pure TiO₂ layer.     

可见光驱动的Ti基半导体光催化剂的研究进展

半导体光催化技术在太阳能转换以及环境治理方面具有巨大潜力。TiO₂由于其高的光催化效率、良好的稳定性以及合适的带边电位等,成为了当前研究最多的光催化材料。但TiO₂是宽带隙半导体,对可见光几乎不响应,这极大限制了TiO₂的应用。为了提高TiO₂对可见光的响应能力,提高太阳能的转化效率,相继开发了一系列由TiO₂衍生的Ti基可见光催化剂。首先简单地介绍了半导体光催化机制,然后综述了Ti基半导体光催化剂的分类、增强可见光响应策略以及Ti基可见光催化剂应用现状,最后总结了Ti基可见光催化剂制备及应用过程中所面临的挑战,同时也对未来Ti基可见光催化剂的合成及发展进行了展望。