High photocatalytic activity of Cu_2O/TiO_2/Pt composite films prepared by magnetron sputtering

Cu_2O/TiO_2/Pt three-layer films were deposited on glass substrates using magnetron sputtering method.The surface morphology and the optical properties of the composite film were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), ultravioletvisible spectroscopy(UV-Vis) and photoluminescence spectroscopy(PL). The photocatalytic activity of the samples was evaluated by the photocatalytic degradation of methyl orange(MO) aqueous solution under visible light irradiation. The results indicate that the Cu_2O/TiO_2/Pt composite films are made up of three layers which are Pt layer,anatase-TiO_2 layer and Cu_2O layer from bottom to top. The surface of the films is even and composed of regular-shaped spherical particles. The photocatalytic activity of the Cu_2O/TiO_2/Pt three-layer film is much higher than that of the Cu_2O/TiO_2 double-layer film. Such enhancement is ascribed to the presence of Pt layer, which further inhibits the photogenerated electron-hole recombination, prolongs the lifetime of the photogenerated carriers, increases the quantum efficiency and hence improves the photocatalytic activity of the film effectively.     

Performance Enhancement in Dye-Sensitized Solar Cells with Composite Mixtures of TiO2 Nanoparticles and TiO2 Nanotubes

In the present investigation,a new composite nanostructured photoanodes were prepared using TiO₂ nanotubes（TNTs） with TiO₂ nanoparticles（TNPs）.TNPs were synthesized by sol-gel method,and TNTs were prepared through alkali hydrothermal method.Dye-sensitized solar cells（DSSCs） were fabricated with different photoanodes comprising of various ratios of TNTs + TNPs,synthetic indigo dye as photosensitizer,PMII（l-propyl-3-methylimidazolium iodide） as ionic liquid electrolyte and cobalt sulfide as counter electrode.The structures and morphologies of TNPs and TNTs were analyzed through X-ray diffractometer,transmission electron microscope and scanning electron microscopes.The results of the investigation showed that the DSSC-4 made with composite photoanode structure（TNTs/TNPs）（90% of TNPs + 10% of TNTs） had improved photocurrent efficiency（2.11%） than pure TNPs（1.00%） and TNT film（0.78%）.Electrochemical impedance spectra revealed that the composite TNTs/TNPs film-based DSSCs possessed the lowest charge-transfer resistances and longest electron lifetime.Hence,it could be concluded that the composite TNTs/TNPs photoanode facilitates the charge transport rate and enhances the efficiencies of DSSCs.     

Enhance of TiO_2 dopants incorporated reduced graphene oxide via RF magnetron sputtering for efficient dye-sensitised solar cells

In particular, the dye-sensitised solar cells(DSSCs) have a high potential in the rational energy conversion efficiency to secure our sustainable energy source.In the present study, advanced radio frequency(RF) magnetron sputtering technique was applied to incorporate titanium dioxide(TiO_2) dopants into reduced graphene oxide(rGO) nanosheet for improving the power conversion efficiency(PCE) of DSSCs device. An optimum TiO_2 content incorporated onto rGO nanosheet plays an important role in improving the PCE of DSSCs by minimising the recombination losses of photo-induced charge carriers.Based on the results obtained, 40-s sputtering duration for incorporating TiO_2 dopants onto rGO nanosheet exhibits a maximum PCE of 8.78% than that of pure rGO film(0.68%). In fact, the presence of optimum content of TiO_2 dopants within rGO nanosheet could act as mediators for efficient separation photo-induced charge carriers. However, the excessive of sputtering duration(e.g. 60 s) of TiO_2 dopants onto rGO nanosheet results higher charge recombination and lowers the PCE of DSSCs(5.39%).     

Dye-sensitized solar cells based on Cr-doped TiO_2 nanotube photoanodes

The effect of chromium doping on the photovoltaic efficiency of dye-sensitized solar cells(DSSCs) with anodized TiO_2 nanotubes followed by an annealing process was investigated. Cr-doped TiO_2 nanotubes(CrTNs) with different amounts of chromium were obtained by anodizing of titanium foils in a single-step process using potassium chromate as the chromium source. Film features were investigated by scanning electron microscopy(SEM), X-ray diffraction(XRD), energy-dispersive X-ray spectroscopy(EDX), and ultraviolet-visible(UV-Vis) spectroscopy. It is clearly seen that highly ordered TiO_2 nanotubes are formed in an anodizing solution free of potassium chromate, and with a gradual increase in the potassium chromate concentration, these nanotube structures change to nanoporous and compact films without porosity. The photovoltaic efficiencies of fabricated DSSCs were characterized by a solar cell measurement system via the photocurrent-voltage(I-V) curves. It is found that the photovoltaic efficiency of DSSCs with CrTNsl sample is improved by more than three times compared to that of DSSCs with undoped TNs. The energy conversion efficiency increases from 1.05 % to 3.89 % by doping of chromium.     

Fabrication of polypyrrole/TiO2 nanocomposite via electrochemical process and its photoconductivity

Size-controllable and vertically-oriented TiO₂ nanotube (TNT) arrays were fabricated using anodic oxidation method from pure titanium sheets in electrolyte solutions. Then with the TNT arrays as the working electrode, a thin film of polypyrrole (Ppy) was synthesized into the TNT arrays via the electrochemical polymerization. During the process, the appearance of redox peaks in cyclic voltammetry curves of the resulting films indicates the occurrence of polymerization. The morphology, the molecular structure, crystallization and optical properties of the TNT arrays and the resulting polymer were investigated by field-emission scanning electron microscopy (FESEM), X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), and UV-vis spectrum analysis, respectively. A dual-layered photoreceptor containing the nanocomposite film as the charge generation layer (CGL) was designed and fabricated. It is found that the photoreceptor based on Ppy/TiO₂ nanotubes as CGL exhibits remarkable photoconductive performance.     

A phenylenevinylene copolymer with perylene bisimde units as organic sensitizer for dye-sensitized solar cells

An alternating phenylenevinylene copolymer P with perylene bisimide units has been used as organic sensitizer to fabricate dye-sensitized solar cells (DSSCs) based on porous and TiCl₄ modified TiO₂ photoelectrodes. As a consequence of the compact layer formed by TiCl₄ treatment to the porous TiO₂ thin film layer, an efficient electron network was formed. Dark current measurements and electrochemical impedance spectra (EIS) suggested that modified photoelectrode significantly reduced the recombination rate of electrons with redox couple in the electrolyte due to the reduced bare FTO surface and longer electron lifetime as compared to the porous TiO₂ photoelectrode. The power conversion efficiency of DSSCs utilizing this copolymer as sensitizer is about 2.60% and 3.98% with porous and modified TiO₂ photoelectrodes, respectively.     

Preparation of doping metal TiO2 particle/nanotube composite layer and their applications in dye-sensitized solar cells

Dye-sensitized solar cells (DSSCs) are composed of a dye-adsorbed nanoporous TiO₂ layer on a fluorinedoped tin oxide (FTO) glass substrate, redox electrolytes, and a counter electrode. DSSCs are constructed through the application of nano-metals and TiO₂ nanoparticle/TiO₂ nanotube (TNT) composite particles with various compositions. The use of oxide semiconductors in the form of nanorods, nanowires, and nanotubes is an interesting approach to improve electron transport through the film. In addition, a suitable amount of TNT in the film could provide a large surface area for the adsorption of the dye. A nano-metal is proposed, wherein the conduction band (CB) prohibits the trapping effects of electrons within the TiO₂ conduction band. This result is attributed to the prevention of electron recombination between the electrons in the TiO₂ conduction band with dye or electrolytes. A TiO₂ composite layer was coated onto FTO glass using a screen-printing method. The dye-sensitized solar cells were fabricated using N719 ruthenium (II) dye and I₃/I₃ ^? electrolyte. The impedance results indicate improved electron transport at the TiO₂/dye/electrolyte interface. The DSSC based on the Fe₂O₃/TiO₂/TNT composite particle hybrids exhibits better photovoltaic performance than the cell made from only TiO₂ nanoparticles.     

Band gap engineering of TiO2 nanostructure-based dye solar cells (DSCs) fabricated via electrophoresis

This work describes a simple method utilizing electrophoretic deposition (EPD) as versatile technique to deposit of commercial TiO₂ (P25) nanopartcles (NPs) films on the fluoride-doped tin oxide (FTO) substrate. The main goal of this study is investigating the effects of surface treatment on the properties of nanoporous P25 electrodes in order to efficiently control and optimize the main fabrication step of the dye-sensitized solar cells (DSSCs). In order to increase of the electron transfer efficiency in DSSC, post-treatment of P25 films using TiCl₄ has been carried out. As a result, cell efficiencies were improved about 40%. Solar cells based on a core–shell structure, including a ZnO as shell and a P25 as core, have been investigated. Results demonstrated that ZnO/P25 film electrode was enable to enhance of short-circuit photocurrent density (J_SC) and consequently solar conversion efficiency for a DSSC by 10%, compared to those of a DSSC containing a bare P25 film electrode. The results were attributed to increase the concentration of free electrons in the conduction band (CB) of P25.     

Coupling system application in photocatalytic degradation of methylorange by TiO_2, TiO_2/SiO_2 and TiO_2/SiO_2/Ag

Three different photocatalysts including TiO_2,TiO_2/SiO_2 and TiO_2/SiO_2/Ag were synthesized via sol-gel growth method,in which colloidal silica was used as Si source,titanium tetra iso-propoxide(TTiP) as titanium source,Ag~+ as dopant ion and hydroxypropyl cellulose(HPC) as dispersant.The purpose was to study the enhancement of photocatalytic activity of TiO_2 by deposition on SiO_2 colloids and also doping with Ag ion.The catalysts were characterized using X-ray diffraction(XRD),transmission electron microscopy(TEM),X-ray fluorescence(XRF),Fourier transform infrared spectroscopy(FT-IR)and Brunauer-Emmett-Teller(BET) methods.It is confirmed that the major phase in all catalysts is anatase.Photocatalytic activity was studied in various conditions for degradation of methylorange(as a model pollutant) to evaluate the effect of some parameters on degradation efficiency.Studying the degradation process in various pH values reveals that the degradation is more efficient in acidic solution than alkaline condition.Coupling the photocatalytic process with some fields called electro-photochemical(EP),magnetic-photochemical(MP) and ultrasonic-photochemical(UP) was studied at two pH values which were compared with photochemical(P) alone.It is concluded that in most cases,the EP is the best coupled system and has the maximum efficiency.Liquid chromatography-mass spectrometry(LC-MS)analysis was used to check the complete decomposition of methylorange at the end of process.     

Enhanced thermoelectric performance of Bi_2Se_3/TiO_2 composite

Bi_2(Te,Se)_3 alloys are conventional commercial thermoelectric materials for solid-state refrigeration around room temperature.In recent years,much attention has been paid to various advanced thermoelectric composite materials due to the unique thermoelectric properties.In this work,Bi_2Se_3/TiO_2 composites were prepared by hot pressing the plate-like Bi_2Se_3 powders coated in situ with hydrolyzed hytetabutyl-n-butyl titanate(TNBT),and therefore numerous TiO_2 in micrometer size could be formed on the interface of Bi_2Se_3 grains.The carrier concentration in Bi_2Se_3 matrix is optimized subject to the addition of n-type semiconductor TiO_2,contributing to a significant improved power factor.In the meantime,the lattice thermal conductivity is also suppressed due to the enhanced phonon scattering at Bi_2Se_3/TiO_2 interface and amorphous TiO_2 particles.As a consequence,a peak figure of merit(zT) of 0.41 is obtained at 525 K in Bi_2Se_3/15 mol% TiO_2 composites,nearly 50% augment over the pristine Bi_2Se_3 binary compound.     

Photocatalytic and photochemical processes of AgCl/TiO_2 studied with a fully integrated X-ray photoelectron spectrometer

A fully integrated X-ray photoelectron spectrometer(XPS) was employed for the investigation of the separation processes and recombination behaviors of photogenerated electrons and holes on the surface of AgCl and ultra-small nano-titanium oxide cluster composite photocatalyst(AgCl/TiO_2).A facile route,by direct colloidal synthesis,for preparing AgCl/TiO_2 with high stability and enhanced visible light(Vis) driven catalytic activity was reported.The photocatalytic activity of AgCl/TiO_2,which revealed that the photo-degradation rate of the as-prepared AgCl/TiO_2 was nearly 10.5 times higher than that of bare AgCl,was evaluated by applying it to the photo-degradation of methyl orange(MO) in water solution.Moreover,AgCl/TiO_2 exhibited an outstanding long-term stability during ten cycles of photo-degradation.The band gap of AgCl decreased from 3.25 to 2.85 eV because of the ultrasmall nano-TiO_2 clusters that were pinned to its surface.The results indicate that the band gap narrowing and surface plasmon resonance(SPR) of Ag(0) were two major contributors to the enhancement of the photocatalytic activity of AgCl/TiO_2 by improving the utilization of Vis.In situ XPS analysis was,therefore,certified as a beneficial method to explore the catalytic mechanism of photocatalysts.     

氮掺杂TiO_2薄膜光催化剂的制备

采用溶胶-凝胶法,在电场热处理条件下,合成了晶粒度为50～60 nm的在可见光下具有较高催化活性的一种掺N的TiO_2薄膜.光催化实验表明:在可见光催化下,掺N薄膜对甲基橙溶液的催化活性大大提高了.通过XPS和XRD分析,确定了N在TiO_2中以取代O原子的形式存在,即薄膜中形成了非整比化合物TiO_(2-x)N_x,通过紫外可见光谱(UV-VIS)分析测试薄膜的透光率,观察到掺N薄膜的吸收截止波长为550 nm,说明吸收边发生了红移.以取代形式掺杂的N在窄化带隙和提高光催化活性方面具有重要的意义.     

复合溶胶电泳制备TiO_2涂层的研究

研究了由TiO_2颗粒和TiO_2溶胶组成的复合TiO_2溶胶,以及其电泳制备涂层的光催化性.实验发现复合溶胶的Zeta电位小于相应的溶胶Zeta电位.对于溶胶在不同温度下煅烧制备的TiO_2粉末进行XRD表征,结果表明随着煅烧温度升高,粉末结晶程度提高,从200 ℃开始出现锐钛矿TiO_2晶相,在550 ℃出现金红石型TiO_2.光催化性能表明,由溶胶而得到的TiO_2涂层的光催化性能要好于复合TiO_2溶胶的光催化性能.     

Ag/TiO_2纳米复合材料的制备及结构研究

首先采用化学氧化在块体Ti表面制备出多孔纳米TiO2,随后通过高能离子束轰击实现Ag纳米粒子在TiO2表面的有效固定,最终在Ti表面制备出Ag/TiO2纳米复合材料。采用XRD、SEM及TEM手段对其进行了结构表征。结果表明,化学氧化法可制备出多孔纳米TiO2,其晶粒尺寸为10 nm左右;通过调节高能Ar离子束轰击的时间,可对TiO2晶粒尺寸进行小范围有效控制。     

Ni—P镀层磷含量对Ni—P／TiO2复合膜耐蚀性能的影响

采用化学镀／溶胶一凝胶技术在碳钢表面制备了低磷（Ni—LP／TiO2）、中磷（Ni-MP／TiO2）和高磷（Ni-HP／TiO2）Ni—P／TiO2复合膜．采用X衍射分析仪和环境扫描电镜表征了Ni—P／TiO2复合膜的结构与形态．应用动电位极化和极化阻力（Rp）测量研究了复合膜在0．5mol／l,H2SO4溶液中的耐蚀性能。实验结果表明Ni—P／TiO2复合膜耐蚀性能优于Ni-P镀层,随NiP镀层磷含量的增加,Ni—P／TiO2复合膜的耐蚀性增强。Ni—HP／TiO2复合膜在0．5mol/L H2SO4溶液的自腐蚀电流密度（icorr）为3．15μA·cm^-2,分别为Ni—LP／TiO2和NiMP／TiO2复合膜的40％和62％;其Rp为11．72kΩ·cm^2．分别为Ni—LP／TiO2和Ni—MP／TiO2复合膜的1．5倍和1．3倍,Ni—HP／TiO2复合膜较NiLP／TiO2和Ni—MP／TiO2复合膜有更佳的耐蚀性能。     

退火温度及TiO_2结构对羟基磷灰石的沉积诱导作用

采用阳极氧化法在钛金属表面制备TiO2薄膜,将表面改性的钛金属在过饱和钙化溶液中浸泡,在其表面沉积羟基磷灰石,研究了退火处理温度对TiO2薄膜晶型转变的影响以及TiO2的晶型结构对羟基磷灰石的诱导沉积作用。研究表明,300℃退火处理,TiO2薄膜为板钛矿相,500℃退火处理转变为锐钛矿相,高于500℃退火处理,锐钛矿相开始向金红石相转变。其中锐钛矿相的TiO2对羟基磷灰石的沉积具有最好诱导作用,沉积物分布均匀,板钛矿相对羟基磷灰石的诱导作用最差,所形成的沉积层是由片状的羟基磷灰石围成的多孔结构。     

阳极电压对医用钛材微弧氧化的影响

采用恒压模式微弧氧化对医用钛材表面改性，制备出含钙磷的TiO2复合膜层，借助于SEM、XRD和EDS研究了阳极电压对膜层的形貌、相组成和钙磷含量的影响，探讨了膜层表面和孔内钙磷的分布规律。研究结果表明，低压处理获得小孔径和锐钛矿型TiO2为主的膜层，钙磷含量和钙磷比较低，并且微孔内的钙磷含量少于膜层表面。随着阳极电压的提高，膜层的孔径增大，金红石型TiO2增多，钙磷含量和钙磷比增大。高压处理时微孔内的钙磷含量与膜层表面相当。提高微弧氧化恒压电压，可以促进Ti氧化反应。经过微弧氧化后的Ti表面多孔形貌、晶型和钙磷含量将对后续的水热处理羟基磷灰石的生成有重要影响。     

Controllable synthesis and tunable photocatalytic activity of TiO_2 nanowires via alcohol-thermal method

Titania nanowires(TiO_2-NW) with tunable aspect ratios and morphologies were directly synthesized using a simple alcohol-thermal technique. Specifically,ethanol and acetic acid were used as solvents and lithium ion was used as the capping agent to promote the conversion of titanium butoxide into TiO_2-NW. The morphologies and crystal phases of TiO_2-NW were determined by the molar ratio of solvents and the content(mol%) of lithium ion. The band gap of TiO_2-NW with pure anatase phase is slightly bigger than that of TiO_2-NW with a mixture of anatase and rutile phases. All TiO_2-NW could achieve effective decolorization of methyl blue(the decolorization rate is over 95%) after 35-min ultraviolet(UV) irradiation.     

Anatase TiO2 sols derived from peroxotitanium acid and to form transparent TiO2 compact film for dye-sensitized solar cells

Transparent and surfactant-free TiO₂ sols containing anatase nanocrystals were prepared by the hydrothermal treatment of water-soluble peroxotitanium acid (PTA) at a temperature of 120 °C. The TiO₂ nanocrystals were characterized by transmission electron microscopy (TEM). The TEM results indicated that the TiO₂ nanocrystals were nanorod-like with diameters of less than 7 nm after the subsequently hydrothermal treatment. A gradient layer between the transparent fluorine doped SnO₂ (FTO) layer and the porous titanium dioxide nanocrystalline film for dye-sensitized solar cells (DSSCs) photoelectrodes, was made with the as-prepared TiO₂ sols. The TiO₂ gradient layers were characterized by field-emission scanning electron microscopy and UV-vis absorption spectrometry. After the gradient layer deposition on the FTO coated glass, the composite multilayer film exhibited the visible light transmittance of 80% which approached to that of bare FTO glass. The photo-to-electric energy conversion efficiency of the N719 dye-sensitized solar cell had significantly improved from 4.2% to 5.6% in the presence of the compact layer between FTO and the porous TiO₂ nanocrystalline film under of AM1.5 illumination (100 mW/cm²). The remarkable improvements in short-circuit current for the DSSCs was due to the effective gradient layer at the FTO-TiO₂ interface which prevented direct contact of electrolytes with FTO and consequently reduced charge recombination losses.     

二氧化钛纳米粉体的可控水热合成研究

采用TiCl_4为原料,用水热法合成了二氧化钛纳米粉体,讨论了水热反应条件对二氧化钛粉体结构和微观形貌的影响.结果表明:在0.5～1.0 mol/L TiCl_4, 130～190 ℃, 3～9 h的水热条件下,合成的TiO_2纳米粉体属于金红石相;TiO_2的形貌和尺寸与原料浓度、反应时间和反应温度密切相关,随着原料浓度的增加、反应温度的升高以及反应时间的延长,TiO_2形貌由球形纳米粒子向纳米棒转变,其尺寸也随之增大.