Dye-sensitized TiO2@SBA-15 composites: Preparation and their application in photocatalytic desulfurization

Photocatalytic oxidation desulfurization has become a research hotspot in recent years because of mild reaction conditions, less energy consumption and high selectivity. In this paper, TiO2 was loaded onto SBA-15 molecular sieves and sensitized with organic dyes(2, 9-dichloroquinacridone, DCQ) to extend its spectral response range from ultraviolet light to visible light. The catalyst DCQ-X%TiO2@SBA-15 was characterized by BET measurements, X-ray diffraction, Fourier transform infrared spectroscopy and Ultraviolet-visible diffuse reflection spectra, and then it was applied for photocatalytic oxidation desulfurization of gasoline. The effects of different catalytic systems, TiO2 concentration, catalyst dosage, and different model sulfur compounds on catalytic desulfurization performance were investigated. Experimental results show that DCQ-TiO2@SBA-15 has a better performance than the unsensitized TiO2@SBA-15, and the desulfurization rate can reach up to 96.1% in a reaction time of 90 min.

Influence of TiCl_4 treatment on performance of dye-sensitized solar cell assembled with nano-TiO_2 coating deposited by vacuum cold spraying

Titanium tetrachloride (TiCl4) treatment was employed to TiO2 coating deposited on fluoride-doped tin oxide (FTO) conducting glass and indium oxide doped tin oxide (ITO) conducting glass, respectively. The nano-crystalline TiO2 coating was deposited using a composite powder composed of polyethylene glycol (PEG) and 25 nm TiO2 particles by vacuum cold spraying (VCS) process. A commercial N-719 dye was used to adsorb on the surface of TiO2 coating to prepare TiO2 electrode, which was applied to assemble dye-sensitized solar cell (DSC). The cell performance was measured under simulated solar light at an intensity of 100 mW·cm-2. Results show that with an FTO substrate the DSC composed of a VCS TiO2 electrode untreated by TiCl4 gives a short-circuit current density of 13.1 mA·cm-2 and an open circuit voltage of 0.60 V corresponding to an overall conversion efficiency of 4.4%. It is found that after TiCl4 treatment to the VCS TiO2 electrode with an FTO substrate, the short circuit current density of the cell increases by 31%, the open-circuit voltage increases by 60 mV and a higher conversion yield of 6.5% was obtained. However, when an ITO substrate is used to deposit TiO2 coating by VCS, after TiCl4 treatment, the conversion efficiency of the assembled cell reduces slightly due to corrosion of the conducting layer on the ITO glass by TiCl4.

Preparation and performance of dye-sensitized solar cells based on ZnO-modified TiO_2 electrodes

The ZnO-modified TiO2 electrode was prepared by adding Zn（CH3COO）2·2H2O to the TiO2 colloid during the sol-gel production process, and was used in dye-sensitized solar cells （DSCs）. The open circuit voltage （Voc） and fill factor （if） of the cells were improved sig- nificantly. The performances of the ZnO-modified TiO2 electrode such as dark current, transient photocurrent, impedance, absorption spectra, and fiat band potential （Vfb） were investigated. It is found that the interface charge recombination impedance increases and Vfb shifts about 200 mV toward the cathodic potential. The effect mechanism of ZnO modification on the performance of DSCs may be that ZnO occupies the surface states of the TiO2 film.

A Bi-layer Composite Film Based on TiO_2 Hollow Spheres, P25,and Multi-walled Carbon Nanotubes for Efficient Photoanode of Dye-sensitized Solar Cell

A bi-layer photoanode for dye-sensitized solar cell(DSSC) was fabricated, in which TiO_2 hollow spheres(THSs) were designed as a scattering layer and P25/multi-walled carbon nanotubes(MWNTs) as an under-layer. The THSs were synthesized by a sacrifice template method and showed good light scattering ability as an over-layer of the photoanode. MWNTs were mixed with P25 to form an under-layer of the photoanode to improve the electron transmission ability of the photoanode. The power conversion efficiency of this kind of DSSC with bi-layer was enhanced to 5.13 %,which is 14.25 % higher than that of pure P25 DSSC.Graphical Abstract A bi-layer composite photoanode based on P25/MWNTs-THSs with improved light scattering and electron transmission, which will provide a new insight into fabrication and structure design of highly efficient dyesensitized solar cells.

Synthesis and application of TiO_2 single-crystal nanorod arrays grown by multicycle hydrothermal for dye-sensitized solar cells

TiO2 is a wide band gap semiconductor with important applications in photovoltaic cells. Vertically aligned Tit2 nanorod arrays （NRs） are grown on the fluorine-doped tin oxide （FTO） substrates by a multicycle hydrothermal synthesis process. The samples are characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, high-resolution transmission electron microscopy （HRTEM）, and selected-area electron diffraction （SAED）. It is found that dye-sensitized solar cells （DSSCs） assembled by the as-prepared Tit2 single-crystal NRs exhibit different trends under the condition of different nucleation and growth concentrations. Optimum cell performance is obtained with high nucleation concentration and low growth cycle concentration. The efficiency enhancement is mainly attributed to the improved specific surface area of the nanorod.

Dye-sensitized TiO2 Solid Solar Cell Using Poly (4-vinylphenyloxy-methyltriphenylamine) as Hole Transport Material

A dye-sensitized TiO2 solid solar cell, which contains poly(4-vinylphenyloxy-methyltriphenylamine) in hole transport layer (HTL) doped with LiSCN and methyl-hexyl-imidazolium iodide (MHIml), was prepared. The solar cell shows that the conversion efficiency is 0.59%, Jsc is 3.03mA/cm2, and V^ is 0.53V at 1 sun light intensity.

Facile fabrication of TiO_2 nanoparticle–TiO_2 nanofiber composites by co-electrospinning–electrospraying for dye-sensitized solar cells

We report a facile method for the fabrication of TiO2 nanofiber-nanoparticle composite （FP） via. simulta- neous electrospraying and electrospinning for dye-sensitized solar cell （DSC） applications. The loading of nanoparticles on the fibers is controlled by varying their feed rates during electrospinning. The FP composites having three different particle loading are prepared by the methodology and the FP with the highest particle loading （denoted as FP-3 in the manuscript） showed the best overall efficiency of 9.15% in comparison to the other compositions of the FP （FP-2, 8.15% and FP-1, Z51%, respectively） and nanofibers （F） and nanoparticles （P） separately （7.21 and 7.81, respectively）. All the material systems are characterized by spec- troscopy, microscopy, surface area measurements and the devices are characterized by current-voltage （I-V）, incident photon-to-current conversion efficiency （IPCE）, electrochemical impedance measurements, etc. I-V, dye-loading and reflectance measurements throw light on the overall performance of the DSC devices.

Effect of hydroxyl on dye-sensitized solar cells assembled with TiO_2 nanorods

YiO2 nanorods have been prepared on ITO substrates by dc reactive magnetron sputtering technique. The hydroxyl groups have been introduced on the nanorods surface. The structure and the optical properties of these nanorods have been studied. The dye-sensitized solar cells （DSSCs） have been assembled using these TiO2 nanorods as photoelectrode. And the effect of the hydroxyl groups on the properties of the photoelectric conversion of the DSSCs has been studied.

Theoretical Study on Electronic, Optical, and Charge Transfer Properties of Starburst Triphenylamine as Sensibilizer @TiO2 Cluster for Dye-sensitized Solar Cells

Here, a series of starburst triphenylamine(WD8) derivatives for dye-sensitized solar cells(DSSCs) applications have been designed. The frontier molecular orbitals(FMOs) property, absorption spectra, and charge transfer rate property of WD8 and its derivatives were simulated. We also evaluated the FMOs energies and absorption spectra of WD8 and its derivatives with the TiO2 cluster. The simulation results show that the phenothiazine-triphenylamine and 2-cyanoacetic acid groups in the ortho-position will increase the HOMO energy, decrease the LUMO energy, and narrow the HOMO-LUMO gap of WD8. The charge injection from WD8 and its derivatives to TiO2 should be more favorable. The phenothiazine-triphenylamine and 2-cyanoacetic acid groups in the ortho-position will decrease the electron and hole injection barriers of WD8. The phenothiazinetriphenylamine and 2-cyanoacetic acid groups in the ortho-position will improve the absorption spectra properties of WD8. The absorption spectra of WD8 and its derivatives with the TiO2 cluster would have a red shift. The phenothiazine-triphenylamine and 2-cyanoacetic acid groups in the ortho-position will increase the charge transfer property of WD8.

Dye-sensitized solid-state solar cells fabricated by screen-printed TiO_2 thin film with addition of polystyrene balls

The screen-printed nanoporous TiO2 thin film was employed to fabricate dye-sensitized solid-state solar cells using CuI as hole-transport materials. The solar cell based on nanoporous TiO2 thin film with large pores formed by the addition of polystyrene balls with diameter of 200 nm to the TiO2 paste exhibits photovoltaic performance enhancement, which is attributed to the good contact of CuI with surface of dye-sensitized thin film due to easy penetration of CuI in the film with large pores.

Effects of Metal Oxide Modifications on Photoelectrochemical Properties of Mesoporous TiO2 Nanoparticles Electrodes for Dye-Sensitized Solar Cells

Mesoporous TiO2 （m-TiO2） nanoparticles were used to prepare the porous film electrodes for dye-sensitized solar cells, and a second metal oxide （MgO, ZnO, A1203, or NiO） modifi- cation was carried out by dipping the m-TiO2 electrode into their respective nitrate solution followed by annealing at 500 ℃. Experimental results indicated that the above second metal oxide modifications on m-TiO2 electrode are shown in all cases to act as barrier layer for the interracial charge transfer processes, but film electron transport and interfacial charge recombination characteristics under applied bias voltage were dependent significantly on the existing states and kinds of these second metal oxides. Those changes based on sec- ond metal oxide modifications showed good correlation with the current-voltage analyses of dye-sensitized solar cell, and all modifications were found to increase the open-circuit photo- voltage in various degrees, while the MgO, ZnO, and NiO modifications result in 23%, 13%, and 6% improvement in cell conversion efficiency, respectively. The above observations indi- cate that controlling the charge transport and recombination is very important to improve the photovoltaic performance of TiO2-based solar cell.

Influence of Modification of Counter Electrode on PhotoelectricProperties of Dye-sensitized TiO_2 Solar Cells

A dye-sensitized nanocrystalline TiO 2 solar cell(DYSC) was assembled, of which counter electrode was modified already by platinum, nickel and carbon. It was found that the DYSC had better photoelectric performance when the electrode was modified by platinum than by nickel and carbon. The influence of the incidence light wavelength on the incidence monochromatic photoelectric conversion efficiency(IPCE) was investigated. The result shows that the IPCE mainly depends on the short-circuit current density(I SC) of a DYSC, and the IPCE reaches 48.32% under the irradiation with the wavelength of 560 nm when the counter electrode of a DYSC was modified by platinum. The influence of incident light intensity on the photoelectric properties of a DYSC was also investigated. It was found that the I SC and open-circuit voltage(V OC) increased and the fill factor(f f) of the DYSC decreased with the increase of the incident light intensity.

Triton Facilitated Spherical TiO₂Nanoparticles and Their Advantage in a Dye-Sensitized Solar Cell

Spherical TiO2 particles (60 nm) were obtained by using a Triton X-100. The surfactant was employed in two stages, i.e., in the hydrolysis of TiCl4 and then in the precipitation of the corresponding Ti (IV) polymers. The advantages of such spherical TiO2 particles were examined in terms of photovoltaic characteristics of a dye-sensitized solar cell (DSSC) using Orange IV dye as sensitizer. Significantly higher overall solar energy conversion efficiency was obtained for a DSSC using the film of these spherical TiO2 particles, compared with that of a cell using a TiO2 film prepared without surfactant.

ZnO Spin-Coating of TiO₂Photo-Electrodes to Enhance the Efficiency of Associated Dye-Sensitized Solar Cells

Dye-sensitized solar cells (DSSCs) with ZnO spin-coated TiO2 photo-electrodes are compared to DSSC with a bare TiO2 photo-electrode. It is demonstrated that the deposited ZnO of controlled amount, by varying the precursor concentration in the coating sol, can indeed enhance the performance of the DSSC. The measured power conversion efficiency shows a maximum around the precursor concentration 0.1 M and falls down sharply to 0% beyond this point. The results are interpreted on the basis of two competing factors: At ZnO concentrations less than 0.1 M, the formation of an energy barrier increases the photocurrent by reducing the rate of interfacial back-recombination. At ZnO concentrations greater than 0.1 M, the screening of the TiO2 film by thicker ZnO layers decreases the photocurrent through the reduction of TiO2 dye-adsorption efficiency.

Electrophoretic Deposition of Titanium Oxide Nanoparticle Films for Dye-Sensitized Solar Cell Applications

Films of titanium oxide nanocrystalline particles (P25) were deposited using an electrophoretic deposition. The film’s characteristics were tuned for applications in dye-sensitized solar cells. Electrophoretic deposition allows control of film characteristics such as porosity and thickness by changing deposition parameters, such as the electric field and deposition time. To increase the efficiency of the dye-sensitized solar cells with films created using electrophoretic deposition, the problem of an electrolyte contamination in the film, which occurred during deposition, was addressed. With the proper chemical post treatment, efficiency of 2.93% with fill factor of 0.55 was obtained when the films were annealed at 450℃. A low annealing temperature of 150℃ resulted in efficiencys of 1.99% with fill factor of 0.68. When the P25 was replaced by hydrothermally fabricated titanium oxide nanocrystalline particles, efficiency of 4.91% with fill factor of 0.55 was obtained.

Evaluation of Reaction Mechanism for Photocatalytic Degradation of Dye with Self-Sensitized TiO₂under Visible Light Irradiation

The dye-sensitized TiO2 method is one of the most promising methods for the visible-light-induced detoxification of pollutants. The reaction mechanism for photocatalytic degradation of orange II (OII) and rhodamine B (RhB) with self-sensitized TiO2 under visible light irradiation (λ > 400 nm) has been evaluated. Radical scavenger studies were carried out to investigate the active species involved in the photodegradation of 5 mg/L of initial concentration of OII and RhB at room temperature. The trapping effects of different scavengers results proved that the oxidation of OII and RhB mainly occurred by the direct oxidization of h+ and ·O2- radicals, while the ·OH radicals played only a relatively minor role in the direct oxidization process.

TiO_2/膨润土光催化降解有机污染物

用溶胶-凝胶法制备了一系列TiO2/膨润土光催化剂(不同负载量和不同焙烧温度),以罗丹明B(RhB)为模型化合物,通过测定染料吸光度和体系化学需氧量(COD)变化,来研究它们在紫外光照射下降解有机污染物的性能.评价结果表明,负载量为50%和焙烧温度为400℃的催化剂Ti400样品降解RhB活性较好,虽然其矿化活性略小于P25(光照4hP25的COD变化为99.7%,400℃焙烧的TiO2/膨润土催化剂Ti400的COD变化为97.0%),但是TiO2/膨润土催化剂更易于回收再利用.用Ti400做催化剂降解RhB,连续循环使用7次,其催化活性基本不变.用XRD、BET和紫外可见漫反射(UV-Vis DRS)等方法对这些催化剂进行了表征.表征结果表明催化剂比表面积大有利于催化活性的提高.

离子掺杂对纳米TiO2薄膜光催化活性的影响研究

研究了Ag^+、Cu^2+、La^3+、Ni^2+及W^6+ 5种离子掺杂对釉面瓷砖表面TiO2薄膜光催化活性的影响，并采用XRD和UV—VIS检测技术对所制备的TiO2薄膜材料进行了表征。结果表明，掺杂离子能有效提高TiO2薄膜的光催化活性，且离子的掺杂存在一个最佳浓度。UV—VIS及XRD衍射发现，掺杂后的纳米TiO2薄膜有不同程度的吸收光谱带边蓝移及粒径减小的现象，具有量子尺寸效应。

氨气热处理对TiO2自组装薄膜光催化性能的影响

利用静电自组装工艺制备了结构有序的TiO2／PSS纳米多层膜，并在不同工艺条件下对薄膜进行热处理。利用UV—ViS吸收光谱、XRD、α台阶膜厚测试仪等手段对薄膜的性能进行了表征，研究了工艺条件对薄膜光催化性能的影响。结果表明：TiO2／PSS纳米多层膜在450℃氨气气氛中热处理后具有很好的光催化性能，薄膜的响应深度约为120nm，热处理过程中氨气流量小所得薄膜光催化性能佳。

Fabrication of TiO2 nanofiber assembly from nanosheets（TiO2-NFs-NSs） by electrospinning-hydrothermal method for improved photoreactivity

Hierarchically structured nanomaterials have attracted much attention owing to their unique properties.In this study,TiO2 nanofibers assembled from nanosheets(TiO2-NFs-NSs)were fabricated through electrospinning technique,which was followed by hydrothermal treatment in NaOH solution.The effect of hydrothermal reaction time(0-3 h)on the structure and properties of TiO2 nanofibers(TiO2-NFs)was systematically studied,and TiO2-NFs was evaluated in terms of the photocatalytic activity toward photocatalytic oxidation of acetone and the photoelectric conversion efficiency of dye-sensitized solar cells.It was found that(1)hydrothermal treatment of TiO2-NFs in NaOH solution followed by acid washing and calcination results in the formation of TiO2-NFs-NSs;(2)upon extending the hydrothermal reaction time from 0 h to 3 h,the BET surface area of TiO2-NFs-NSs(T3.0 sample)increases 3.8 times(from 28 to 106 m2 g^-1),while the pore volume increases 6.0 times(from 0.09 to 0.54 cm3 g^-1);(3)when compared with those of pristine TiO2-NFs(T0 sample),the photoreactivity of the optimized TiO2-NFs-NSs toward acetone oxidation increases 3.1 times and the photoelectric conversion efficiency increases 2.3 times.The enhanced photoreactivity of TiO2-NFs-NSs is attributed to the enlarged BET surface area and increased pore volume,which facilitate the adsorption of substrate and penetration of gas,and the unique hollow structure of TiO2-NFs-NSs,which facilitates light harvesting through multiple optical reflections between the TiO2 nanosheets.