Photocatalytic Activity Of TiO2 Films Research Articles

Influence of Non-Ionic Surfactant and Silver on the Photocatalytic Activity of TiO2 Films for Degradation of Dyes in Distilled and Tap Water

Influence of Non-Ionic Surfactant and Silver on the Photocatalytic Activity of TiO2 Films for Degradation of Dyes in Distilled and Tap Water

SYNTHESIS OF Ag-MODIFIED TiO2 SOL-GEL FILMS AND ITS APPLICATION AS PHOTOCATALYSTS FOR METHYLENE BLUE DEGRADATION

In the study, the photocatalytic activity of TiO2 films that are created by dip-coating from a sol that contained titanium (IV) isopropoxide, monoethanolamine, and 2-methoxyethanol is demonstrated. Through photo-fixation of Ag (I) ions with varied concentration (10-2 - 10-4 M) in the water phase under UV illumination, the films are subsequently surface-modified with Ag co-catalyst layers. Scanning Electron Microscopy (SEM), X-Ray Photoelectron Spectroscopy (XPS), Ultraviolet-Visible (UV) Spectroscopy, and Electron Paramagnetic Resonance (EPR) techniques are used to physically characterize the samples. Results reveal that the modification of the co-catalyst had no impact on the thickness and porosity of the films. In addition, the study show that the modified TiO2 films had increased photocatalytic activity. All the characterization methods used have shown the formationof surface - bound Ag (I) species and metallic silver nanoclusters. By measuring the Methylene Blue (MB) dye degradation under UV light illumination, as - prepared and Ag -modified TiO2 films are evaluated for their photocatalytic activity, and the impact of the silver precursor concentration during photo-fixation is investigated.The highest catalytic activity is seen for films that have been modified at a concentration of Ag (I) of 10-2 M. Ordered from highest to lowest, the MB photodegradation rate constants are TiO2 < TiO2 /Ag, 10-4 < TiO2 /Ag, 10-3 < TiO2 / Ag, 10-2.

A New Study on the Effect of Pure Anatase TiO2 Film Thickness on Gentian Violet Photodegradation Under Sunlight: Considering the Effect of Hole Scavengers

In this paper, pure anatase TiO2 thin films were grown on glass substrates by using sol-gel dip-coating method. To study the physical, chemical and optical properties of the deposits, TiO2 thin films were synthesized with thickness (241.5, 258.19, 230.33 and 302.35 nm). XRD patterns show that TiO2 films were grown with unique anatase phase (101). The photocatalytic test shows that film (~ 302 nm) gives high photodegradation of gentian violet (GV) under sunlight irradiation due to the low number of defect sites. The increase in film thickness and the decrease of surface roughness and crystal size decrease the number of defect sites in the material which lead to low recombination rate of charge carriers. The use of Ag+ as hole scavenger increases the photocatalytic activity 4.75 times within the first hour. The photocatalysis process showed that Ag+ can be reduced on the surface of photoactivated TiO2 thin films to obtain sun-photodeposited/dip-coated AgO/TiO2 (p-n) heterojunction. HIGHLIGHTS Pure anatase TiO2 thin films were successfullysynthesized via sol-gel dip-coating method High thickness (302 nm) of TiO2 thin film exhibits high photocatalytic activity for photodegradation of GV under sunlight irradiation The presence of Ag+ in wastewater shows high photocatalytic activity of TiO2 films with 4.75 times within the first hour The possibility of sun-photodeposited/dip-coated of (p-n) AgO/TiO2 heterojunction is discussed GRAPHICAL ABSTRACT

A dual effect of surface roughness and photocatalysis of crystalline TiO2-thin film for self-cleaning application on a photovoltaic covering glass

A high level of transparency and rich self-cleaning thin film of TiO2 on glass substrates were synthesized using the dip-coating method. The preferred orientation (1 0 1) and (2 0 0) peaks corresponding to 2θ value of 25° and 48° respectively, confirm the anatase phase of TiO2. Surface roughness value of 9 nm has been found using atomic force microscope (AFM), which effectively prevents dust accumulation on TiO2 coated surface. Moreover, to understand soiling effect of film, TiO2 coated and uncoated substrates were investigated and compared after one week of soiling in the coal dust region. Interestingly, the TiO2-coated substrates showed 8% more transmittance than the uncoated films. Furthermore, four adhesion forces between dust particles and film surfaces were calculated. The smaller adhesion forces were inspected for the TiO2 coated thin films compared to the bare glass substrate, which designates lower dust accumulation on the substrate. In addition, the photocatalytic activity of TiO2 film showed 39.40% and 53.06% methylene blue (MB) dye degradation efficiency under sunlight and UV light exposure respectively, that helps in cleaning the surface by reacting with dirt. Our study suggests that TiO2 coated thin film is a potential candidate for self-cleaning in solar cell applications due to its high transparency, smaller particle size, lower adhesion forces and better photocatalytic activity.

Hydrothermal synthesis of rutile TiO2 nanotubes film on Ti foil for photocatalytic degradation

One-dimensional TiO2 nanotubes film was synthesized on the Ti foil oxidized at 800℃ by hydrothermal method in a highly alkaline solution. The crystal structure, morphology and chemical state of the samples were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope and X-ray photoelectron spectroscopy. The result indicates that the TiO2 nanotubes film still remains rutile phase structure after hydrothermal treatment. The growth mechanism of TiO2 nanotubes is also discussed that includes dissolution, nucleation and growing process. The photocatalytic activity of TiO2 film is remarkably improved after hydrothermal reaction. Due to the one-dimensional tubular structure, TiO2 nanotubes film hydrothermally synthesized for 6 hours displays the highest photocatalytic degradation rate of methylene blue

Preparation and Photocatalytic Activity of TiO2 Film with High Exposure {001} Crystalline Surface

TiO2 films with exposed {001} crystal surface were prepared by hydrothermal method with 10 mm * 20 mm * 0.15 mm titanium sheet as titanium source and substrate and HF as shape control agent. The films were characterized by (XRD), (SEM) and (UV-VIS). The results showed that the TiO2 films with high exposure {001} crystal surface could be obtained by using 0.01 mol/L HF, 11:5 mixture of water and isopropanol as solvent, hydrothermal reaction temperature of 180°C, reaction time of 3H and calcination at 450°C for 2h. In this paper, methylene blue was used as probe and xenon lamp was used as light source to study the photocatalytic activity of TiO2 film.

A Review on the Pathways of the Improved Structural Characteristics and Photocatalytic Performance of Titanium Dioxide (TiO2) Thin Films Fabricated by the Magnetron-Sputtering Technique

Titanium dioxide (TiO2) thin films are used for a broad range of applications such as wastewater treatment, photocatalytic degradation activity, water splitting, antibacterial and also in biomedical applications. There is a wide range of synthesis techniques for the deposition of TiO2 thin films, such as chemical vapor deposition (CVD) and physical vapor deposition (PVD), both of which are well known deposition methods. Layer by layer deposition with good homogeneity, even thickness and good adhesive nature is possible by using the PVD technique, with the products being used for photocatalytic applications. This review studies the effects of magnetron sputtering conditions on TiO2 films. This innovative technique can enhance the photocatalytic activity by increasing the thickness of the film higher than any other methods. The main purpose of this article is to review the effects of DC and RF magnetron sputtering conditions on the preparation of TiO2 thin films for photocatalysis. The characteristics of TiO2 films (i.e., structure, composition, and crystallinity) are affected significantly by the substrate type, the sputtering power, the distance between substrate and target, working pressure, argon/oxygen ratio, deposition time, substrate temperature, dopant types, and finally the annealing treatment. The photocatalytic activity and optical properties, including the degree of crystallinity, band gap (Eg), refractive index (n), transmittance (T), and extinction coefficient (k), of TiO2 films are dependent on the above- mentioned film characteristics. Optimal TiO2 films should have a small particle size, a strong degree of crystallinity, a low band gap, a low contact angle, a high refractive index, transmittance, and extinction coefficient. Finally, metallic and nonmetallic dopants can be added to enhance the photocatalytic activity of TiO2 films by narrowing the band gap.

Photocatalytic activity of TiO2 films prepared by cathodic arc deposition: Dependence on thickness and reuse of the photocatalysts

In this work, the photocatalytic activity of anatase films with thicknesses up to 1100 nm prepared by cathodic arc deposition (CAD) on glass substrates is reported. The photocatalytic activity under UV–Vis irradiation (λ > 330 nm) was evaluated through the efficiency in the reduction of 0.80 mM Cr(VI) in the presence of 1 mM ethylenediaminetetraacetic acid (EDTA) at pH 2, and compared with the performance of samples obtained by dip-coating using commercial P25. The CAD films were optically transparent, with visible light transmittance ≥ 50% even for the thickest samples. The photocatalytic efficiency of the films increased as the thickness increased. The possibility of obtaining thicker films allowed cathodic arc films reaching better performance than P25 samples. For the most active films obtained by CAD, complete Cr(VI) reduction could be obtained in <300 min under a 28 W m−2 UV-A irradiance. The photocatalytic reaction for all the studied TiO2 films obeyed pseudo-first order kinetics. A decrease of the reaction rate constant was observed for both types of films after reusing the photocatalysts. The fate of the reduced Cr(VI) was also analyzed.

EFFECTS OF ANNEALING ON THE COMPOSITION, STRUCTURE AND PHOTOCATALYTIC PROPERTIES OF C-DOPED TITANIA FILMS DEPOSITED BY REACTIVE MAGNETRON SPUTTERING USING CO2 AS CARBON SOURCE

Carbon-doped titania (C:TiO2) films were prepared by reactive magnetron sputtering using CO2 as a carbon source. The as-prepared films were annealed at different temperatures in vacuum condition. A TiO2 film using O2 gas was also prepared for comparisons with C:TiO2. The structure and composition of the as-prepared, the TiO2 films and the annealed C:TiO2 films were analyzed by X-ray diffraction and X-ray photoelectron spectroscopy, whereas the surface morphology of the C:TiO2 films was measured by atomic force microscopy. Furthermore, photocatalytic properties of the films were evaluated by the degradation of methyl orange (MO). The results indicate that the photocatalytic property was improved when carbon was doped into TiO2 films, and the C:TiO2 films consist of anatase and TiO phases. The experimental results of the MO’s degradation confirm that the annealing process at various temperatures can modify the surface morphology of the films and the content of oxygen vacancies in the films. Consequently, the variations in surface topography and oxygen vacancy potentially enhance the photocatalytic activity of TiO2 films.

Micro-patterned TiO2 films for photocatalysis

Titanium dioxide film as a stable material plays an important role in photocatalytic degradation of pollutants. One of the ways to improve photocatalytic efficiency is to increase the active sites on the semiconductor surface. Photolithography is a manufacturing technique for controlling precisely micrographics on surface. Here grating-structured, square-structured and hexagon-structured TiO2 films were prepared by photolithography and the effects of various surface structures on photocatalysis were studied. It was demonstrated that the photocatalytic activity of TiO2 film was not always improved as the surface area increased. The micro-patterned surface would also impede the mass transfer in the process of photocatalysis.

Synthesis of gadolinium-doped TiO2 thin films by sol–gel spin coating technique and its application in degradation of rhodamine-B

ABSTRACTIn this research, a sol–gel spin coating method was employed to prepare pure and gadolinium (Gd)-doped TiO2 thin films on microscopic glass slides. The structure and morphology of prepared thin films were characterised by X-ray diffraction (XRD), scanning electron microscope (SEM) equipped with energy-dispersive X-ray analyser, UV–VIS absorption spectroscopy, atomic force microscope and Brunauer–Emmett–Teller (BET) surface area techniques. The sol–gel-fabricated thin films were employed for degradation of Rhodamine-B (RhB) dye under UV light irradiation. XRD results revealed that the synthesised films were crystalline and in anatase phase. The blue shift in the absorption spectra was observed with increase in Gd concentration up to 4 wt%. The BET surface area of doped films was more compared to pure TiO2 films. The amount of Gd3+ had a great impact on the photocatalytic activity of TiO2 films and Gd-TiO2 (4 wt%) films exhibited the optimal photocatalytic degradation. About 99% of RhB degradation was observed within 50 min of UV irradiation. The effect of the addition of inorganic anions and electron acceptors on degradation was also studied. The sol–gel-synthesised Gd-TiO2 films can be used as an effective catalyst for degradation of various other organic compounds under UV light irradiation.

Enhanced effect of a plasma‐irradiated titanium substrate on the photocatalytic activity of a TiO2 film

To improve the photocatalytic activity of TiO2 film, Ti substrates are irradiated by He ions with different incident ion energy, temperature, and fluence. Anatase TiO2 films are then coated on the plasma‐irradiated substrates via chemical vapor deposition followed by calcination. Photocurrent tests and photocatalytic oxidation (PCO) of formaldehyde are used to assess photocatalytic performance. The optimal plasma‐irradiated samples showed a four times higher photocurrent and a three fold increase in the rate constant of the PCO reaction compared to the TiO2 coated, untreated control sample. It is found that the enhanced photocatalytic activity and photocurrent are related to the changes of Ti crystal structure and surface morphology through plasma irradiation.

Characterization of TiO2 films obtained by a wet chemical process

Abstract TiO2 has an easily tunable bandgap and a great absorption dye ability being widely used in many fields and in a number of fascinating applications. In this study, a wet chemical route, particularly a sol gel method using spin-coating is adopted to deposit TiO2 thin films onto soda lime glass and silicon substrates. TiO2 films were prepared by using an alcoholic solution of analytical reagent grade TiCl4 as titanium precursor at various experimental conditions. The accent was put on the conditions of preparation (spin time, spin speed, precursor concentration, number of coating layers etc), doping and on the post-deposit treatment namely the drying and the crystallization. The results showed a strong dependence on the drying temperature and on the temperature and duration of the crystallization. We found that the solution preparation and its color are important for getting a reproducible final product. The Raman spectra recorded at room temperature, showed the characteristic peaks of anatase which appear at 143 and around 396 cm−1. These peaks confirm the presence of TiO2. The X-ray diffraction (XRD) was used to identify the crystalline characteristic of TiO2 while the chemical states and relative amounts of the main elements existing in the samples were investigated by X-ray Photoelectron Spectroscopy (XPS). The morphology of the samples was visualized by AFM. We show by this work the feasibility to obtain different nanostructured TiO2 by changing the concentration of the solution. Photocatalytic activity of TiO2 films was evaluated. Rhodamine B is a recalcitrant dye and TiO2 was successfully tested for its oxidation. An abatement of 60% was obtained under sunlight for an initial concentration of 10 mg/l.

Enhanced photo-catalytic activity of TiO2 films by removal of surface carbon impurities; the role of water vapor

We have studied the photo-catalytic degradation of acetaldehyde over the surface of TiO2 films under UV light (365nm) irradiation both at dry and humid air conditions using a high vacuum chamber equipped with on-line gas-chromatography as a batch-type reactor. Changes of TiO2 surfaces upon the photo-catalysis experiments were studied by X-ray photoelectron spectroscopy. The competitive adsorption of water and acetaldehyde resulted in the reduction of reaction rate of photo-catalytic degradation of acetaldehyde under the UV light irradiation. The photo-catalytic reaction rate of TiO2 films towards acetaldehyde mineralization increased when the photo-catalysis experiments were performed repeatedly and it was much more pronounced under humid conditions. Our XPS analysis revealed that carbon impurities on the surface of TiO2 films were removed by UV-light driven photo-catalytic mineralization under humid conditions. Water vapor facilitated the photo-catalytic removal of carbon impurities from TiO2 surface generating additional active sites of TiO2 which resulted in the enhanced photo-catalytic activity of TiO2 films.

On the photocatalytic activity of lanthanum impregnated TiO2 films prepared by micro-arc oxidation

TiO2 films were synthesised by microarc oxidation (MAO) process on pure titanium substrate in a phosphate-based electrolyte. Then, La3+/TiO2 composite films have been prepared in lanthanum-containing solution by La3+ impregnation. Effects of the frequency, the concentration of lanthanum and impregnation time on physical and chemical properties of the films were investigated by SEM, XRD, EDS techniques. A UV-vis spectrophotometre was also used to study optical properties of the layers. Results showed that the photocatalytic activity of TiO2 films prepared by MAO was first increased and then decreased with the increasing frequency applied in the experiment. It is indicated that the variation of photocatalytic activity in the TiO2 films was affected by the content of anatase. After the La3+ impregnation, the photocatalytic activity of La3+/TiO2 composite films was greatly improved compared with that of the TiO2 films.

Fabrication of SnO2-TiO2 core-shell nanopillar-array films for enhanced photocatalytic activity

Immobilized or deposited thin film TiO2 photocatalysts are suffering from a low photocatalytic activity due to either a low photon absorption efficiency or a high carrier recombination rate. Here we demonstrate that the photocatalytic activity of TiO2 can be effectively improved by the SnO2-TiO2 core-shell nanopillar-array structure which combines the benefits of SnO2/TiO2 heterojunction and high reaction surface area. The SnO2-TiO2 core-shell nanopillar-array films were fabricated using atomic layer deposition and dry etching techniques via barrier-free porous anodic alumina templates. The photocatalytic activity of the prepared films was evaluated by methylene blue (MB) bleaching under 352nm UV light irradiation. The results show that the photocatalytic activity of TiO2 film was 45% improved by introducing a SnO2 film between TiO2 and ITO glass substrate and was 300% improved by using the SnO2-TiO2 core-shell nanopillar-array structure. The 45% improvement by the SnO2 interlayer is attributed to the SnO2/TiO2 heterojunction which separates the photogenerated electron-hole pairs in TiO2 for MB degradation, and the high photocatalytic activity of the SnO2-TiO2 core-shell nanopillar-array films is attributed to the three dimensional SnO2/TiO2 heterojunction which owns both the carrier separation ability and the high photocatalytic reaction surface area.

Synthesis and characterization of Ag doped TiO2 heterojunction films and their photocatalytic performances

In this study, undoped and silver (Ag) doped titanium dioxide (TiO2) films were successfully synthesized by sol-gel spin coating technique on the Si substrates. Photocatalytic activities of the TiO2 films with different Ag content were investigated for the degradation of methylene blue (MB) under UV light irradiation. The crystal phase structure, surface morphology, chemical and optical properties of Ag-doped TiO2 films were characterized using an X-ray diffractometer (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), UV–vis spectrophotometer, and FTIR spectrophotometer. The results showed that the Ag-doped TiO2 films calcined at 500°C had the crystalline anatase phases and the surface morphologies with some cracks. Ag substitution into TiO2 matrix enhanced the photocatalytic activity of TiO2 films under UV light irradiation as compared to the undoped TiO2 film. Furthermore, the results indicated that the 0.7% Ag doped TiO2 film exhibited a superior photocatalytic activity than that of undoped and other Ag-doped TiO2 films. This study demonstrated the potential of an application of Ag doped films to efficiently treat dissolved organic contaminants in water.

Photocatalytic activity of TiO2 film containing Fe2O3 via plasma electrolytic oxidation

This study investigated the photocatalytic activity of an Fe containing TiO2 film produced in the FePO4 electrolyte via the plasma electrolytic oxidation (PEO) method. For this purpose, the PEO process was carried out on titanium substrate under ac condition in two different alkaline electrolytes containing K3PO4 and FePO4 respectively. The structure, chemical composition and constituent phases of the PEO treated samples were analysed via SEM, X-ray photoelectron spectroscopy and X-ray diffraction. The optical properties of the samples were also examined by an ultraviolet–visible spectrophotometer. In terms of the photocatalytic activity judging from the decomposition of methylene blue under visible light illumination, the sample formed in the FePO4 electrolyte was better than that in the K3PO4 electrolyte due to the incorporation of an Fe compound that has a narrow band gap.

Photocatalytic activity of TiO2 films immobilized on aluminum foam by atomic layer deposition technique

The aim of the this work was to study feasibility of titanium dioxide thin films prepared by atomic layer deposition (ALD) technique on aluminum foam substrates for photocatalysis and compare performance of thin films with commercially available AEROXIDE® TiO2. Formic acid and phenol photocatalytic decomposition was monitored using high-pressure liquid chromatography (HPLC). The morphology and thickness of TiO2 films were characterized by scanning electron microscopy (SEM) and their structure was determined by X-ray diffraction (XRD). Surface of the thin films was characterized with Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). The amount of TiO2 deposited on aluminum foam was measured by inductively coupled plasma optical emission spectroscopy (ICP-OES). It was observed that initial rates of formic acid and phenol degradation were 0.007 and 0.001 mmol L−1 min−1, respectively. The apparent quantum yields for formic acid using immobilized and reference TiO2 powder (AEROXIDE® TiO2 P25, Evonik) were 2.2 and 2.7%, correspondingly. While for phenol apparent quantum yield was equal to 0.4% when TiO2 thin film was used and 0.7% in the case of reference powder. A decrease of the photocatalytic activity of TiO2 films deposited on aluminum foam was observed after the first cycle for both model compounds. It was suggested from this study that suppression of activity occurs due to detachment of TiO2 from the surface of thin film.

Enhanced Raman scattering and photocatalytic activity of TiO2 films with embedded Ag nanoparticles deposited by magnetron sputtering

Nanoaprticles(Nps)-Ag/TiO2 multilayer films with different working pressures of Ag and inserted SiO2 shell layers between Ag and TiO2 were prepared by alternate magnetron sputtering. The formation of Ag nanoparticles embedded in TiO2 matrix was confirmed by the XRD and TEM results. The optical absorption peaks assigned to the surface plasmon resonance (SPR) of Ag nanoparticles were observed in the wavelength range of 550–750 nm. With increasing working pressure of Ag, the SPR peaks show blue-shift due to the decreasing Ag Nps size and increasing spacing between them. Compared with the pure TiO2 film, the Nps-Ag/TiO2 and Nps-Ag/SiO2/TiO2 film show significantly enhanced Raman scattering due to the strong local field induced by the SPR of Ag nanoparticles, and the enhanced photocatalytic activity of Nps-Ag/TiO2 film is related with the improved charge separation by the embedded Ag nanoparticles.