Porous TiO2 Films Research Articles

Electro-Assisted Photocatalytic Degradation of Methyl Orange on TiO<sub>2</sub> Film Using NaCl as Electrolyte

Porous and smooth TiO2 film electrodes prepared by sol-gel method were used on methyl orange degradation by an electro-assisted photocatalytic degradation process. When using the applied potential along, there was no obvious degradation of methyl orange whether using TiO2 film electrode prepared using PEG template or not. The largest difference between the two electrodes appears at potential of 0.7 V in 0.05 mol/l NaCl solution, and the porous electrode shows better degradation activity in electro-assisted photocatalytic degradation. When NaCl concentration was 0.07 mol/l, degradation rates on porous and smooth film electrodes were 51.16% and 32.35 %, respectively. After 100 min of irradiation, 90% of the methyl orange degraded on the porous TiO2 film electrode, and 79.87% of the methyl orange degraded on the smooth TiO2 film electrode.

Photocatalytic disinfection of P.aeruginosa bacterial Ag-doped TiO2 film

TiO2 and TiO2-Ag composites films were prepared by sol–gel method and coated on glass fibre roving. The surface morphology and properties of synthesized composites films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR) and UV-vis diffuse reflectance spectroscopy (DRS). The antibacterial activity studies of TiO2 and TiO2 composite films were evaluated by photocatalytic reaction against P.aeruginosa bacteria. The results shown that pure TiO2 and TiO2 porous (TiO2-PEG) films have disinfection efficiency 57% and 93% within 15min under UV irradiation, respectively. TiO2-1Ag film has highest antibacterial effect under UV irradiation and that disinfectionefficiency is 100% within 10min. It has been found that Ag doped TiO2 films have the higher disinfection efficiency than that of pure TiO2 due to the effect of silver species.

Photocatalytic superhydrophilic TiO2 coating on glass by electrospinning

A photocatalytic, superhydrophilic, transparent, porous TiO2 film consisting of rice-shaped nano/mesostructures deposited on glass substrates by electrospinning has been developed. Optical properties such as transmittance and absorbance, as well as the superhydrophilicity and self-cleaning properties (photocatalysis) of the deposited TiO2 film are studied. The water contact angle decreases with increase in the thickness of the TiO2 resulting in superhydrophilic transparent coatings which may be used for applications in window coatings and photovoltaic modules. The self-cleaning property of the TiO2 film consisting of rice-shaped nano/mesostructures is compared with that of commercially available Degussa P-25 in the photodegradation of Alizarin red dye and found to be more effective.

Highly porous TiO2 films for dye sensitized solar cells

Highly porous nanoparticle films were investigated as alternative working electrode morphology for the synthesis of dye sensitized solar cells (DSSCs). These films were rapidly assembled by flame synthesis and direct aerosol deposition of TiO2 nanoparticles with high specific surface area. Structural–functional analysis of their properties revealed that the film porosity is a key parameter greatly determining the resulting energy conversion efficiency (η). In fact, aerosol deposition at low substrate temperatures (∼100 °C) led to very high porosity (ε = 98%) and weak film cohesion. These films were easily resuspended upon immersion in the dye and/or electrolyte solutions resulting in very poor performances (η = 0.08%). In contrast, allowing for partial nanoparticle sintering by deposition at moderate temperatures (∼400 °C) decreased the film porosity from 98 to 95% leading to higher mechanical stability and partially preserving the large surface required for dye adsorption. As a result, these films had drastically higher current density (12.2 mA cm−2) and overall performances (η = 5%) representing an 8 times improvement with respect to the best reported for similar highly porous morphologies. Remarkably, their conversion efficiency decreased only slightly with increasing film thickness reaching 4.6% at 128 µm. This unique attribute suggests that high film porosity may inhibit recombination losses enabling utilization of thick films with enhanced light absorption properties.

Investigation on the energy conversion of dye-sensitized solar cells based on TiO2 core/shell using metal oxide as a barrier layer

Photo-electrochemical solar cells based on a core-shell structure including ZnO shell and TiO2 cove, have been fabricated with ruthenium bipyridyl complex (N719) as the sensitizer. Compared with the pure anatase TiO2, the ZnO-covered TiO2 film possesses outstanding ability to transport electrons with an overall power conversion efficiency of 3.72. Elctrochemical study shows that surface modification of TiO2 film with ZnO can increase the concentration of free electrons in the conduction band of TiO2. This remit implies that the charge recombination is reduced in process of electron transport through the TiO2 porous film, which can decrease the photocurrent loss and hence improve Dye-Sensitized solar ceils (DSSCs) efficiency. This result indicates that optimization of TiO2 porous network fabrication condition is efficient, for the improvement of TiO2 based DSSC’s performances.

Sensing of Vaporous Organic Compounds by TiO2 Porous Films Covered with Polythiophene Layers

AbstractThis paper describes the detection of volatile organic compounds (VOCs) through analyses of two output signals from integrated microcantilever sensor arrays coated with organic‐inorganic hybrid sensing layers. The surface of TiO2 porous films was modified by amphiphilic terthiophene monomers and the adsorbed monomers were polymerized at the surface of TiO2 nanoparticles. The TiO2 porous films covered with polythiophene layers worked as highly sensitive sensing interfaces to provide two output signals for weight and resistance changes during exposure to VOC vapor. When the TiO2 porous films onto the sensor arrays were dyed with various kinds of amphiphilic monomers with different substituents, the resulting films provide exact information on VOC concentration from the mass changes as well as VOC classification from the analyses of response patterns.

Porous TiO<sub>2</sub> Films Prepared by Sol-Gel Method Using Different Kinds of Templates

Porous TiO2 films were prepared through dip-coating on glass substrates using several different templates. Dip-coating process was optimized to prepare the three layered films. The film prepared with PEG1000 has the maximum activity compared with the other films using CTAB and HST. While PEG molecular weight is in the range from 400 to 6000, methyl orange degradation rate reaches its maximal value when using PEG1000. Two comparatively high activities can be found at the ratios of PEG1000:PEG400 as 3:1 and 1:2. The 1:2 ratio is the optimal one. PEG1000 seems to be more suitable of being used as a template to prepare porous TiO2 film with high photocatalytic activity. After 200 min of irradiation, 98.6 % of the initial dye can be degraded on the film prepared using 2 g of PEG1000.

Calcination Conditions Influencing the Preparation of Porous TiO<sub>2</sub> Film Using PEG1000 as Template

TiO2 porous film was dip-coated on glass substrate by sol-gel process using PEG1000 as template. The influences of calcination temperature and time were investigated. The absorption edges of the films calcinated at different temperatures have no obvious change, but the transmittances of the films can be affected. Methyl orange degradation rates are 30.1%, 33.8% and 38.3% on the films prepared at 450 oC, 480 oC, and 500 oC, respectively. The film calcinated at 500 oC for 2 h has the highest transmittance and the highest activity on methyl orange degradation, while the films calcinated for less or more than 2 h have much lower activities. After 30 min of irradiation, 38.3% of the initial methyl orange in the solution can be degraded on the porous TiO2 film calcinated at 500 oC for 2 h.

Synthesis and photocatalytic properties of porous TiO2 films prepared by ODA/sol–gel method

Porous TiO2 films were deposited on SiO2 pre-coated glass-slides by sol–gel method using octadecylamine (ODA) as template. The amount of ODA in the sol played an important role on the physicochemical properties and photocatalytic performance of the TiO2 films. The films prepared at different conditions were all composed of anatase titanium dioxide crystals, and TiO2 crystalline size got larger with increasing ODA amount. The maximum specific surface area of 41.5m2/g was obtained for TiO2 powders prepared from titanium sol containing 2.0g ODA. Methyl orange degradation rate was enhanced along with increasing ODA amount and reached the maximal value at 2.0g addition of ODA. After 40min of UV-light irradiation, methyl orange degradation rate reached 30.5% on the porous film, which was about 10% higher than that on the smooth film. Porous TiO2 film showed almost constant activity with slight decrease from 30.5% to 28.5% after 4 times of recycles.

Ethanol and methanol sensing characteristics of Nb‐doped TiO2 porous thin films

AbstractUndoped and Nb‐doped TiO2 porous thin films have been obtained through a sol–gel method using analytical grades Ti(OiC3H7)4 and Nb(OC2H5)5 as precursors. The morphology, crystalline microstructure, and the sensing properties towards ethanol and methanol of the obtained thin films have been investigated. The effects of the dopant on the film morphology and on alcohol sensing properties are discussed. Both direct current (DC) and alternating current (AC) measurements were performed at different temperatures in methanol and ethanol ambients to better understand the mechanisms of the alcohol detection. In the presence of a small amount of Nb, the activation energy for electrical conduction decreased. Nb doping improves the selectivity for methanol in the temperature range of 300–400 °C. The Nyquist diagrams showed complex phenomena during alcohol detection.

Tribological Characterization of Porous TiO<sub>2</sub> Coatings Produced by Electrodeposition

In this work, the resistance to scratch and wear (pin-on-flat) tests of five different porous TiO2 films were compared. Such tribological tests were carried out under dry conditions. The coatings were electrodeposited on commercially pure-Ti by anodic oxidation method in different electrolyte solutions at constant voltages. The scratch tests were conducted by applying increasing normal loads up to 400 mN. The coefficient of friction (COF) varied from 0.2 up to 0.5, and increased at larger penetrations depths. When the electrolyte concentration was changed from 0.5 into 1.0M H2SO4, the COF slightly decreased. Scanning electron microscopy indicated that the coatings produced in H2SO4/150V and Na2SO4/100V did not have their substrates revealed. In addition, the samples anodized in H2SO4/150V had the highest elastic recoveries. Therefore, such coatings seem to be more resistant to scratch tests than the others. The wear tests were carried out with Berkovich tip as counter-face under constant normal loads of 10 mN in 10 forward-backward cycles. The coatings deposited in H2SO4/150V had the lowest wear volume rates. The findings suggest that the porous Ti oxide coatings electrodeposited above their rupture voltages are more suitable to both scratch- and wear-resistance compared to those prepared at the lowest voltage (H2SO4/100V).

Preparation of porous TiO2 films by means of pulsed laser deposition for photocatalytic applications

Preparation of porous TiO2 films by means of pulsed laser deposition for photocatalytic applications

TiO2 Nanocrystals Synthesized by Laser Pyrolysis for the Up‐Scaling of Efficient Solid‐State Dye‐Sensitized Solar Cells

AbstractA crucial issue regarding emerging nanotechnologies remains the up‐scaling of new functional nanostructured materials towards their implementation in high performance applications on a large scale. In this context, we demonstrate high efficiency solid‐state dye‐sensitized solar cells prepared from new porous TiO2 photoanodes based on laser pyrolysis nanocrystals. This strategy exploits a reduced number of processing steps as well as non‐toxic chemical compounds to demonstrate highly porous TiO2 films. The possibility to easily tune the TiO2 nanocrystal physical properties allows us to demonstrate all solid‐state dye‐sensitized devices based on a commercial benchmark materials (organic indoline dye and molecular hole transporter) presenting state‐of‐the‐art performance comparable with reference devices based on a commercial TiO2 paste. In particular, a drastic improvement in pore infiltration, which is found to balance a relatively lower surface area compared to the reference electrode, is evidenced using laser‐synthesized nanocrystals resulting in an improved short‐circuit current density under full sunlight. Transient photovoltage decay measurements suggest that charge recombination kinetics still limit device performance. However, the proposed strategy emphasizes the potentialities of the laser pyrolysis technique for up‐scaling nanoporous TiO2 electrodes for various applications, especially for solar energy conversion.

Preparation of porous nanoparticle TiO2 films for flexible dye-sensitized solar cells

A TiO2 paste was prepared by mixing commercial TiO2 (P25), ethanol, distilled water and a small amount of Ti (IV) tetraisopropoxide (TTIP), following by a hydrothermal treatment. Before hydrothermal treatment, a stirring for 48 h can prevent cracking TiO2 films. TTIP significantly promote the chemical connection between TiO2 particles and its adherence to the substrate, the TTIP amount of 6 mol% is suitable. UV irradiation can remove some impurities and water from the TiO2 film with an optimal time of 2 h. Transmission electron microscopy, X-ray diffraction, scanning electron microscopy and photovoltaic tests are characterized and measured. Short-circuit current density, open-circuit voltage, fill factor and photoelectric conversion efficiencies for the fabricated flexible dye-sensitized solar cell are 7.20 mA cm−2, 0.769 V, 0.686 and 3.84%, respectively, under irradiation with a simulated solar light of 100 mW cm−2.

Characterization of Porous TiO<sub>2</sub> Films Prepared Using PEG of Different Molecular Weight

Porous TiO2 films were prepared through dip-coating on glass substrates using different molecular weight of PEG. Surface roughness increased with increasing PEG molecular weight. The film prepared with PEG400 was fairly smooth with slight roughness. The films prepared with high molecular PEG became rougher and there were some larger particles on the films. When the PEG molecular weight got higher, adsorption edge of the films tended to move toward shorter wavelength region. In the wavelength range between 350 and 450 nm, larger PEG molecules made higher film transmittance. The particles prepared using higher or lower molecular weight of PEG had less surface area than using PEG1000. The average pore sizes were 14 nm, 15 nm, 28 nm, and 52 nm, and the total pore volume were 0.12 ml/g, 0.13 ml/g, 0.08 ml/g, and 0.09 ml/g for the TiO2 powders prepared using PEG400 to PEG 6000.

Photocatalytic activity enhancement of TiO2 porous thin film due to homogeneous surface modification of RuO2

Abstract

Effect of the Residual Template on Surface Photoelectric Characteristics of Structurally-Ordered Macroporous Nanocrystalline TiO<sub>2</sub>

The Macroporous Nanocrystalline TiO2 Thin Film Was Prepared by Dipping-Coating Method. Polystyrene (PS) Microspheres Template Was Used as Pore-Forming Assistant and TiO2 Sol Was Used as Precursor. the Photoelectric Characteristics of the Samples Were Studied Using Surface Photovoltage (SPV) and Photoacoustic (PA) Techniques. the Presence of a Small Amount of Residual Template Damages the Integrity of the Porous TiO2 Film with Inverse Opal Structure, and TiO2 May Be Restricted in Certain Application Fields as Photonic Crystals. a Small Amount of Residual Template Changes the Surface Photovoltaic Properties of the Porous TiO2 Film, Resulting Mainly in the Broadened Scope and the Increased Intensity of SPV Response.

PEG and ODA as Composite Templates to Prepare Porous TiO<sub>2 </sub>Films by Sol-Gel Method

Porous TiO2 films were prepared through dip-coating on glass substrates using composite templates of PEG and ODA. Photocatalytic activity of the photocatalyst was evaluated by measuring removal rate of aqueous methyl orange under UV light irradiation. The addition of composite templates had obvious influence on surface morphology of the films. Layered and porous structures formed in the surface due to the function of templates. When the amount of PEG in the composite template increased from 0.1 g to 1.9 g, adsorption edge of the films moved to longer wavelength region. When the amount of PEG increased to 1.0 g, there were sharp decrease of specific surface area and cumulative pore volume. The improving photocatalytic activity as a result of addition of PEG can be noticed.

The effect of compression on electron transport and recombination in plastic TiO2 photoanodes

The compression method was applied for the preparation of plastic TiO2 porous films on a conductive indium–tin oxide (ITO)-coated polyethylene naphthalate (PEN) substrate at low temperature for the generation of high-efficiency plastic dye-sensitized solar cells (DSCs). The compression parameters, including pressure and time, were varied in order to determine their effect on the photovoltaic performance of the plastic DSCs. The results from electrochemical impedance spectroscopy (EIS) showed that charge transport resistance in the porous TiO2 films (Rt) gradually decreased when the applied pressure was increased from 0MPa to 150MPa, which indicated a better connection between the TiO2 nanoparticles and electron transport in the TiO2 films. In addition, a longer press time led to an increased resistance of electron recombination (Rct) and an increased charge-collection efficiency. After optimization of the compression parameters, the efficiency of energy conversion was increased by approximately 81.6%. In addition, the efficiency of energy conversion was increased by an additional 4.65% under AM1.5 illumination.

Porous TiO2 Film Electrode Used for Photoelectrocatalytic Degradation of Methyl Orange in NaHCO3 Solution

PEG1000 was used as template to prepare porous TiO2 film by sol-gel method. The functions of applied potential and concentration of NaHCO3 to the photoelectrocatalytic degradation of methyl orange on porous and smooth TiO2 films were investigated. Methyl orange degradation rate has two optimal values at the applied potential of 0.8 V and 1.8 V. The addition of PEG may have negative effect on photoelectrocatalytic activity of TiO2 film. The degradation rate increases with increasing NaHCO3 concentration from 0 up to 0.05 mol/l, and then it declines after further increase of electrolyte concentration. After 100 min of reaction, the degradation rates on the films prepared without and with PEG addition are 63.78% and 65.22%, respectively.