Photocatalytic Properties Of TiO2 Research Articles

Influence of Surfactant on the Crystal Form and Photocatalytic Properties of Nano-TiO<sub>2</sub>

The nano-TiO2 was prepared by adding surfactant chitosan and sodium dodecyl benzene sulfonate (DBS) under hydrothermal conditions. The influence of chitosan and DBS on the crystal form and photocatalytic properties of TiO2 was discussed. Chitosan acted as the chelant in the reaction, while DBS played the function of preventing aggregation of powder and increasing the degree of crystallization. The fixed calcination temperature was 500°C. The crystallite size could reach about 40.1nm upon the addition of 1g chitosan, and the catalytic efficiency was 51.89%. The crystallite size was about 45.8nm upon the addition of 1g DBS, and the catalytic efficiency was 48.13%. The nano-TiO2 had smaller particle size when chitosan was added under the same reaction conditions.

Photocatalytic property of TiO2 sensitized by different crystal phase CdS

TiO2 samples sensitized by different crystal phase CdS (CT) are synthesized by hydrothermal process at different reaction temperature. The samples are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV-Vis diffuse reflectance (UV-Vis). The XRD result reveals that the crystal phase of CdS is transformed from cubic phase to hexagonal phase with the increase of hydrothermal reaction temperature (120–160 °C). The absorption edge of CT is extended from 498 nm to 546 nm. The photocatalytic degradation of rhodamin B (RhB) in aqueous solution is used to evaluate the photocatalytic activity of CT. With the increase of the preparation temperature, the photocatalytic activity of CT becomes stronger. The degradation rate of RhB by CdS/TiO2 at 160 °C (CT-160 °C) reaches 78%.

The Effects of Doping Copper and Mesoporous Structure on Photocatalytic Properties of TiO2

This paper describes a system for the synthesis of Cu-doped mesoporous TiO2nanoparticles by a hydrothermal method at relatively low temperatures. The technique used is to dope the as-prepared mesoporous TiO2system with copper. In this method, the copper species with the form of Cu1+, which was attributed to the reduction effect of dehydroxylation and evidenced by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), was well dispersed in the optimal concentration 1 wt.% Cu-doped mesoporous TiO2. In this as-prepared mesoporous TiO2system, original particles with a size of approximately 20 nm are aggregated together to shapes of approximately 1100 nm, which resulted in the porous aggregate structure. More importantly, the enhancement of the photocatalytic activity was discussed as effects due to the formation of stable Cu(I) and the mesoporous structure in the Cu-doped mesoporous TiO2. Among them, Cu-doped mesoporous TiO2shows the highest degradation rate of methyl orange (MO). In addition, the effects of initial solution pH on degradation of MO had also been investigated. As a result, the optimum values of initial solution pH were found to be 3.

Influence of Nd-Doping on Photocatalytic Properties of TiO2Nanoparticles and Thin Film Coatings

Structural, optical, and photocatalytic properties of TiO2and TiO2:Nd nanopowders and thin films composed of those materials have been compared. Titania nanoparticles with 1, 3, and 6 at. % of Nd-dopant were synthesized by sol-gel method. Additionally, thin films with the same material composition were prepared with the aid of spin-coating method. The analysis of structural investigations revealed that all as-prepared nanopowders were nanocrystalline and had TiO2-anatase structure. The average size of crystallites was ca. 4-5 nm and the correlation between the amount of neodymium and the size of TiO2crystallites was observed. It was shown that the dopant content influenced the agglomeration of the nanoparticles. The results of photocatalytic decomposition of MO showed that doping with Nd (especially in the amount of 3 at. %) increased self-cleaning activity of the prepared titania nanopowder. Similar effect was received in case of the thin films, but the decomposition rate was lower due to their smaller active surface area. However, the as-prepared TiO2:Nd photocatalyst in the form of thin films or nanopowders seems to be a very attractive material for various applications.

Enhanced Photocatalytic Degradation of Salicylic Acid in Water-ethanol Mixtures from Titanium Dioxide Grafted with Hexadecyltrichlorosilane

Abstract The aim of this paper is to study the effect of the chemical modification on the photocatalytic properties of TiO2. The TiO2 Degussa-P25 nanoparticles are chemically modified using the hydrophobic organosilane hexadecyltrichlorosilane (HTS). The samples are employed as catalysts for salicylic acid photocatalytic oxidation in water-ethanol mixtures. The kinetics of salicylic acid photodegradation is investigated as a function of ethanol content in water-ethanol mixtures and initial HTS concentrations. The results indicate that the HTS groups are not degraded during the photocatalytic process. The TiO2 grafted by HTS is more efficient than bare TiO2 for the photodegradation process in presence of ethanol. The photodegradation process follows first order kinetics and the apparent rate constant increases linearly with the initial HTS concentration (amount of HTS grafted).

PHOTOCATALYTIC PROPERTIES OF TiO2/CNTs FILMS WITH DIFFERENT MORPHOLOGY ON STAINLESS STEEL SUBSTRATES

CNTs– TiO 2 films with different morphology were fabricated on stainless steel substrates through chemical vapor hydrolysis deposition (CVHD) process and sol–gel process, respectively. Their morphology was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The photocatalytic properties of the films were tested in the degradation of methyl orange by UV light irradiation. The results revealed that TiO 2 nanoparticles could form a continuous layer on the surface of CNTs through CVHD process. While for sol–gel process, most TiO 2 nanoparticles were isolated and only a small amount of TiO 2 nanoparticles attached on the surface of CNTs. And the photocatalytic property of TiO 2/CNTs film synthesized through CVHD process was better than that of TiO 2/CNTs films synthesized through sol–gel process. Electrochemical impedance spectroscopy (EIS) analysis illuminated that TiO 2/CNTs synthesized through CVHD process displayed a smaller resistance than the sample which was synthesized through sol–gel process and certified that the close combination between TiO 2 and CNTs could minimize recombination of photogenerated electrons and holes, and thus promote the photocatalytic property.

The effects of plasma nitriding pretreatment in steel substrates on the photocatalytic activity of TiO2 films

This paper presents a comparative study of TiO2 films deposited on plasma nitrided and non-nitrided carbon steel substrates. It is well known that plasma nitriding contributes to increase film adhesion and corrosion resistance of the substrate. However, most studies about photocatalytic properties of TiO2 on steel substrates do not address the use of nitrided carbon steel. The main goal of this paper is to investigate the deposition of photocatalytic TiO2 film on nitrided carbon steel, obtained through a duplex treatment of plasma nitriding and reactive plasma sputtering deposition. TiO2 films were deposited on nitrided and non-nitrided AISI 1015 steel samples. The samples were characterized by X-ray diffraction (XRD), profilometry, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The photocatalytic activity was evaluated by monitoring the effect of photoinduced hydrophilicity and through the degradation of methylene blue dye (MB). The pretreatment by plasma nitriding increases the substrate surface roughness and improves the growth of rutile phase. The roughness of the substrate surface affects wettability only when the TiO2 film is not photoactivated. All samples become super-hydrophilic upon UV irradiation and remaining in this state for at least 24h. A slightly higher performance in photocatalysis of MB is obtained by TiO2 film deposited on non-nitrided substrate.

Study of Homologous Elements: Fe, Co, and Ni Dopant Effects on the Photoreactivity of TiO2 Nanosheets

AbstractDespite sustained effort over the years, additional investigations into the relationship between doping elements and the photocatalytic properties of TiO2 are needed. In this work, Fe‐group(Fe, Co, Ni)‐doped anatase TiO2 nanosheets with exposed {0 0 1} facets are prepared by using a facile solvothermal synthetic route. A change in the type and concentration of the doping element consequently leads to a change in the size and percentage of {0 0 1} facets in the TiO2 nanosheets, and finally causes a significant difference in the photocatalytic activities of the as‐prepared TiO2 samples. In this case, the performance of doped TiO2, which serves as the photocatalyst, is investigated by directly assessing its effect on the photodegradation of azo dyes (methylene blue) under UV and visible light irradiation, respectively. Importantly, for the first time these studies reveal that the order of the activities of the doped TiO2 is Ni>Co>Fe, and the optimal value of the percentage of the doping ions to Ti ions is 0.75 %. Electrochemical impedance spectra, photocurrent, and photoluminescence measurements indicate that the charge separation and transportation rate is mainly influenced by the type and concentration of doping ions, which determines the photodegradation activities of the TiO2 host.

TiO2-coated natural zeolite: Rapid humic acid adsorption and effective photocatalytic regeneration

Abstract Natural zeolite coated with titanium dioxide (TiO 2 ) was used as an adsorbent to rapidly remove humic acid (HA) from an aqueous solution. Coating TiO 2 onto zeolite markedly improved its efficiency in adsorbing HA: most of the bulk organic matter (80%) could be removed within 5 min of adsorption by the zeolite/TiO 2 particles at neutral pH, whereas less than 20% was removed by bare zeolite alone. In addition, immobilisation of TiO 2 onto zeolite permitted easier separation of the adsorbent from the treated water. Photocatalytic properties of TiO 2 were exploited for the regeneration of the adsorbent. The adsorbent was shown to be readily regenerated by photocatalytic oxidation and was still effective in removing HA after 5 adsorption/regeneration cycles. These results indicate that TiO 2 -coated zeolite can be a very attractive adsorbent for the rapid removal of HA from aqueous solutions.

Fabrication of multifunctional TiO2–fly ash/polyurethane nanocomposite membrane via electrospinning

In this study, we demonstrate the fabrication of multifunctional composite polyurethane (PU) membrane from a sol gel system containing TiO2 and fly ash (FA) nanoparticles (NPs). The adsorptive property of FA and photocatalytic property of TiO2 can introduce different functionalities on PU mat for water purification. Different types of PU nanofiber mats were prepared by varying the composition of NPs in blend solution. FE-SEM, TEM, TGA, XRD, UV–visible spectra, and water contact angle measurement confirmed the incorporation of FA and TiO2 NPs on/into PU nanofibrous mat. The influence of NPs on PU membrane was evaluated from the adsorption of heavy metals (Hg, Pb), removal of dyes (methylene blue), antibacterial activity, and water flux. The improvement of all these activities is attributed to the adsorptive property of FA and photocatalytic/hydrophilic property of TiO2 NPs. Therefore, as-synthesized composite membrane can be utilized as an economically friendly filter media for water purification.

Synergistic Modification of Electronic and Photocatalytic Properties of TiO2 Nanotubes by Implantation of Au and N Atoms

The structural and electronic properties of N-doped, Au-adsorbed, and Au/N co-implanted TiO2 nanotubes (NTs) were investigated by performing first-principle density functional theory (DFT) calculations. For all the possible implanted configurations, the radius and bond length do not change significantly relative to the clean NTs. Our results indicate that the introduction of N into NTs is in favor of implantation of Au, and Au pre-adsorption on the NTs can also enhance the N concentration in NTs. The synergistic stability can be mainly attributed to charge transfer between Au and N atoms. In co-implanted configurations, the empty N 2p states in the band gap are occupied by one electron; denoted by Au 5s states. Thus, the associated electron transition among the valence band, the conduction band and the gap states results in redshift of the light absorption. In addition, the disappearance of N 2p empty states can effectively decrease the photogenerated carrier combination. Therefore, the Au/N implanted NTs should be regarded as a promising photocatalytic material under the visible light region.

Photocatalytic properties of TiO2 and TiO2/Pt: A sol-precipitation, sonochemical and hydrothermal approach

In this work we prepared TiO2 nano-powders and TiO2/Pt nano-composites via three synthesis methods (sol-precipitation, sonochemical method, hydrothermal method) starting with the same precursors and media. To evaluate and compare the physical properties of the prepared materials, X-ray diffraction analysis, BET measurements, FTIR spectroscopy, X-ray photoelectron spectroscopy (XPS) and electron microscopy (TEM, HRTEM, SAED) were applied. The results showed changes to the TiO2 phase composition and crystallinity, the specific surface area as well as the platinum’s particle shape and size, depending on the method of synthesis. To determine the photocatalytic efficiency of the prepared materials, the photocatalytic discoloration of the methylene blue solution was evaluated using UV–Vis spectroscopy. The important properties required for a high photocatalytic activity, related to the surface characteristics and the phase composition, were determined in terms of the synthesis method. It was concluded that the optimum characteristics were obtained when using the hydrothermal approach, where the TiO2 had two phases, i.e., – anatase and rutile, a Pt-phase in the form of nanoparticles and adsorbed Pt-molecular species, as well as the presence of available free surface hydroxyl groups. Such characteristics had a critical influence on the photocatalytic activity of the final material.

TiO2 hollow microspheres: synthesis, photocatalytic activity, and selectivity for a mixture of organic dyes

The photocatalytic properties of TiO2 have been extensively studied. TiO2 hollow microspheres may be useful for removing organic pollutants from waste water, given their high photocatalytic activities and ease of reclamation. In the work described here, TiO2 hollow microspheres were synthesized by a facile solvothermal method and characterized by XRD, SEM, TEM, and N2 adsorption–desorption isotherm measurements. Their optical properties were investigated using UV–Vis diffuse reflectance absorption spectroscopy. The photocatalytic activity of the as-prepared TiO2 hollow microspheres was evaluated by studying the microsphere-catalyzed photodegradation of an aqueous rhodamine B solution irradiated with simulated sunlight, and comparing the results with those obtained using commercial TiO2 (P25) as the catalyst instead. The selectivity of the catalytic microspheres was studied by applying them in the photodegradation of a mixed dye solution of rhodamine B and 4-(p-nitrophenylazo)resorcinol (Magneson I). The TiO2 hollow microspheres were found to exhibit enhanced photocatalytic activity compared to that of P25, and a much higher photodegradation percentage for rhodamine B than for Magneson I in the mixed solution. Interestingly, the photodegradation percentages of the TiO2 hollow microspheres for rhodamine B and Magneson I in the mixed solution were the same as those observed in a solution of rhodamine B and a solution of Magneson I. That is, the TiO2 microspheres degraded the two dyes simultaneously in the mixed solution with the same high efficiency as they did in separate solutions of each dye. This characteristic would be very useful in practical applications. Moreover, the TiO2 hollow microspheres rapidly settled under gravity and were therefore easy to reclaim. These results suggest that the microspheres represent a promising photocatalyst for use in waste water treatment.

Optical and photocatalytic properties of TiO2 films modified with oxides and gold

AbstractFilms consisting of TiO2/ZrO2/SiO2 undoped and doped with Au nanoparticles were synthesized by the sol‐gel method. The films were characterized with X‐ray diffraction (XRD), scanning electron microscopy (SEM), spectroscopic ellipsometry (SE) and optical absorption (OA) methods. The XRD study demonstrates the formation of TiO2 anatase nanocrystals and Au nanoparticles. SE and OA measurements of the undoped films showed no significant absorption in the spectral range of 400–1000 nm. Doping with Au nanoparticles resulted in the appearance of a surface plasmon resonance (SPR) absorption band at 600 nm as well as weaker absorption bands in the 300–500 nm region. The observed changes in optical properties agreed with the enhanced photocatalytic activity of Au‐doped TiO2/ZrO2/SiO2 films with gold compared to undoped films. The photocatalytic activity was evaluated by the photodegradation of the organic dye Rhodamine B. Under optimized conditions, the photodecomposition rate of the doped films was several times larger than that of the undoped films. Films of TiO2, TiO2/ZrO2/SiO2 and ternary oxides were investigated.

Photocatalytic Properties of TiO2 / WO3 / FTO Multi-layer Structures Prepared by Spray Pyrolysis Deposition

ABSTRACTVisible-light photocatalytic property of TiO2 / WO3 / FTO multi-layer structure was investigated. In this structure, the visible-light absorption takes place in the WO3 layer, and generated electrons and holes diffuse into the FTO and TiO2 layers, respectively. The holes diffused into the valence band of the TiO2 layer produce the hydroxyl radicals due to oxidation of H2O and/or OH− adsorbed on the TiO2 surface. The FTO bottom layer, which acts as a scavenger of electrons, contributes to an effective charge separation. As a result, the visible-light photocatalysis is enhanced in this structure.

Synthesis and SERS Performance of a Recyclable SERS Substrate Based on Ag NPs Coated TiO2 NT Arrays

Titanium dioxide nanotube arrays (TiO2 NTA) are successfully fabricated via a simple method combine two processes: bottom-up hydrothermal growth of ZnO nanorods and displacement reaction of TiO2 NTA. Silver nanoparticles (Ag NPs) are decorated on TiO2 NTA by in situ Sn2+-mediated reduction of Ag(NH3)2 + to Ag NPs. The structure is characterized by Field Emission Scanning Electron Microscope (FESEM), High Resolution Transmission Electron Microscopy (HRTEM). Ag NPs decorated TiO2 NTA (Ag-TiO2) is employed as a SERS-active substrate, which exhibits good SERS intensity and recyclability. The substrate of Ag-TiO2 shows good recyclability as the photo-catalytic property of TiO2, the arrays can clean themselves by photo catalytic degradation of target molecules adsorbed to the substrate under irradiation with UV light into inorganic small molecules.

Structure, Characterization and Photocatalytic Properties of TiO<sub>2</sub> Doped with Different Content of Sn<sup>4+</sup> Ions

Structure, Characterization and Photocatalytic Properties of TiO<sub>2</sub> Doped with Different Content of Sn<sup>4+</sup> Ions

Preparation and Photocatalytic Property of Graphene/TiO2 Composite Powder

Graphene/TiO2 (GR/TiO2) composite powders were prepared by co-precipitation method, and their morphology, structure and photocatalytic property were studied by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction and ultraviolet spectrophotometer, respectively. The experimental results show that the photocatalytic activity of TiO2 is significantly improved by GR. When the content of GR in the composite powder is 7.88%, the GR/TiO2 composite powders treated at 500°C display the good photocatalytic performance in which the degradation volume of methyl orange (MO) approaches 100% within 120 min. The improvement for photocatalytic properties of TiO2 is attributed to the special structure and excellent electrical properties of GR.

Photocatalytic properties of nanostructured titanium dioxide

We describe a process for obtaining tubular nanostructured (nanotubular) titanium oxide by electrochemical anodizing. We have studied the elemental composition of the films formed by x-ray spectral analysis and Auger analysis, and have also studied the photocatalytic properties of TiO2 exposed to UV and visible radiation.

Free-standing open-ended TiO2 nanotube membranes and their promising through-hole applications

Free-standing open-ended TiO2 nanotube membranes were fabricated by raising voltage for a short time at the end of anodization process. Benefiting from its semiconducting nature and distinctive through-hole structure, the applications of open-ended TiO2 nanotube membranes on flow-through photocatalysis and nanoreactor were demonstrated. As for flow-through photocatalysis, the photocatalytic property of TiO2 is beneficial to reduce the concentration of RhB solution during RhB molecules diffuse through open-ended TiO2 nanotube membrane. As for nanoreactor application, CdS@TiO2 core–shell nanocables were successfully fabricated by a simple paired-cell reaction. A possible formation mechanism for the growth of core–shell structure was discussed on the basis of a series of electron microscopy characterization results. In addition, we evaluated the photocatalytic activity of CdS@TiO2 samples synthesized at different reaction time through the degradation of rhodamine B under simulated sunlight irradiation. It was found that the CdS@TiO2 samples synthesized at 24h exhibited about 100% enhanced photocatalytic activity as compared to bare TiO2 nanotubes, while the CdS@TiO2 samples synthesized at 48h (core–shell nanocables) had the equivalent photocatalytic activity to the bare TiO2 nanotubes. Such behavior that the photocalytic activity changes with CdS loading amount results from a compromise between a larger amount of light absorption and a lower efficiency of charge separation, as well as limited diffusion by channel blocking higher degree of CdS loading.