Unsupported TiO2 Research Articles

Development of super-hydrophobic surface using Tio2 to reduce adverse effects of environmental pollutants on buildings

The development of self-cleaning surfaces in recent years has been significant in preserving buildings from environmental contaminants and improving visual durability. Titanium dioxide (or titania), a photocatalyst, is used with cement to improve aesthetic durability and de-pollution properties. Super hydrophilic materials were developed by covering glass, ceramic tiles, or polymers with the semiconducting photocatalyst titanium dioxide (TiO2). Grease, grime, and organic pollutants disintegrate when TiO2 is exposed to light and are simply swept away by water (rain). Ink and vehicle smoke are utilised to evaluate the self-cleaning properties of TiO2-containing concretes, and the oxidation of carbons (COx), gaseous atmospheric pollutants responsible for acid rain and photochemical smog, is explored using nano titanium dioxide. The research allowed for the identification of photo-oxidation mechanisms of stain and COx on TiO2-containing cement, as well as parallels and differences with pure unsupported TiO2. Engineering TiO2 particles with certain crystallite sizes and modifying the photocatalyst electrokinetic properties by changing the overall pKa of the TiO2 surface have both been shown to be efficient approaches for controlling the attractive features of ion-ion correlation forces. The effects on applications in a concrete building, specifically on the exterior surface, to improve overall photocatalytic activity are reviewed. The experimental data on photocatalytic performances measured for regular and nano-coated samples are examined regarding photocatalyst qualities and the effect of cement's chemical environment on titania particles. The research allowed for the identification of photo-oxidation mechanisms of stain and COx on TiO2-containing cement, as well as parallels and differences with pure unsupported TiO2.

Visible Light Activated Fe-N-SiO2/TiO2 Photocatalyst: Providing an Opportunity for Enhanced Photocatalytic Degradation of Antibiotic Oxytetracycline in Aqueous Solution

To probe advantages in Fe-N-SiO2/TiO2 nanocomposite system, the visible photocatalytic degradation of the nonbiodegradable antibiotic oxytetracycline (OTC) by unsupported TiO2 and its modified composites by incorporating each of the Fe, N, and SiO2 dopants under a series of conditions were investigated. The structural and optical properties as well as the morphology of the prepared nanocomposites were also characterized applying Fourier transform infrared (FT-IR), X-ray diffraction, photoluminescence spectroscopy, UV-visible diffuse reflectance spectra and field emission scanning electron microscopy/Energy-dispersive X-ray spectroscopy (FESEM/EDX). In order to develop two models portraying appropriate functional relationships between two main responses (OTC removal efficiency and its specific removal rate (SRR)) and four numerical variables (OTC concentration, catalysis loading, initial pH and reaction time), two separate multivariate analysis pathways under response surface methodology (RSM) were taken. The results obtained all came down to the maximum SRR (220 OTC mg OTC removed/g cat. h) found at the maximum catalyst dosage of 1.5 g/l, and acidic pH of 3 after 0.5 h. Furthermore, the Fe-N-SiO2/TiO2 proved a stable photocatalytic activity during three subsequent reusability experiments, shedding light on its reliable potential for future application.

Preparation of TiO2/Metalosilicate composites via acrylamide gel method and investigation of their photocatalytic performance for degradation of Brown NG

In this work, the photocatalytic degradation of a specific dye as Brown NG (BNG) by using TiO2 nanoparticles (as the photocatalysts), supported on ZSM-5 type metalosilicate (aluminosilicate, ferrisilicate, and chromosilicate) was reported. The supported and unsupported TiO2 samples were synthesized using acrylamide gel technique in the presence of various anions (produced by the used acids in precursor synthesis solution) containing Clˉ, CH3COOˉ, ClO4−, SO42− and NO3−. The prepared samples were characterized by employing X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV–vis diffuse reflectance spectroscopy analysis. XRD analysis results showed that all the used ZSM-5 type metalosilicates (aluminosilicate, ferisilicate, and chromosilicate) for supporting TiO2 nanoparticles could prevent the anatase to rutile transformation after performing calcination at 450 °C. The photocatalytic activities and photodegradation kinetics of the prepared samples were determined by studying the degradation of Brown NG. Considering neat and supported TiO2 samples, pure titania that was prepared in the presence of Clˉ (TECI) and ferrisilicate supported titania that was prepared in the presence of SO42− (TFSI) exhibit the highest photocatalytic efficiency under UV light illumination.

TiO2 Nanoparticle-Loaded Poly(NIPA-co-NMA) Fiber Web for the Adsorption and Photocatalytic Degradation of 4-Isopropylphenol.

A TiO2 nanoparticle-loaded polymer fiber web was developed as a functional material with the ability to adsorb and photo-catalytically degrade organic pollutants in aquatic media. A linear copolymer of N-isopropylacrylamide (primary component) and N-methylol acrylamide (poly(NIPA-co-NMA)) was prepared, and composite fibers were fabricated by electrospinning a methanol suspension containing the copolymer and commercially available TiO2 nanoparticles. The crosslinking of the polymer via the formation of methylene bridges between NMA units was accomplished by heating, and the fiber morphology was analyzed by electron microscopy. 4-Isopropylphenol generated by the degradation of bisphenol A—one of the endocrine-disrupting chemicals—was used as the model organic pollutant. As poly(NIPA) is a thermosensitive polymer that undergoes hydrophilic/hydrophobic transition in water, the temperature-dependence of the adsorption and photocatalytic degradation of 4-isopropylphenol was investigated. The degradation rate was analyzed using a pseudo-first-order kinetic model to obtain the apparent reaction rate constant, kapp. The enhancement of the photocatalytic degradation rate owing to the adsorption of 4-isopropylphenol onto thermosensitive poly(NIPA)-based fibers is discussed in terms of the ratio of the kapp of the composite fiber to that of unsupported TiO2 nanoparticles. Based on the results, an eco-friendly wastewater treatment process involving periodically alternated adsorption and photocatalytic degradation is proposed.

Ru/Rh catalyzed selective hydrogenation of CO2 to formic acid: a first principles microkinetics analysis

Unsupported and oxygen deficient TiO2 surface supported small Rux/Rhx nanoclusters can efficiently and selectively convert CO2 into formic acid.

Hydrogen photo-production from glycerol on platinum, gold and silver-modified TiO2-USY62 catalysts

In this work, photocatalysts consisting of TiO2 supported on zeolite (USY62) were synthesized by sol-gel method and, subsequently, a noble metal (Pt, Au, or Ag) was incorporated by impregnation or photodeposition. Zeolite-TiO2 composites were characterized by SEM, TEM, XRD, N2 adsorption-desorption, Raman and UV–vis spectroscopy, and well-dispersed anatase TiO2 particles (ca. 10 nm) that exhibited a blue-shift in the UV–vis absorption due to the size quantization effect were produced. The photocatalytic activity of all zeolite-TiO2 composites was examined by the photoreforming of aqueous glycerol solution (10% w/w) under UV and solar-simulated radiation. The activity of the zeolitic photocatalysts decreased in the order Pt > Au > Ag, being catalysts prepared by photodeposition more active than those prepared by impregnation. Moreover, Zeolite-supported TiO2, led to a TiO2 with smaller deactivation in H2 production than unsupported TiO2, which can be ascribed to the small TiO2 particle size or an interaction zeolite-TiO2. All in all, a photocatalyst (USY-Ti-PPt) with TiO2 up to four times more active than unsupported TiO2 under UV radiation was prepared.

Porous titanium dioxide supported on glass microbubbles to prepare a low-density photocatalyst for AR1 degradation

Low-density TiO2(C)/GB hollow powders were synthesized by loading anatase TiO2 onto glass microbubbles. CTAB (cetyltrimethyl ammonium bromide) was used to produce pores in the supported TiO2. A TiO2 layer with a thickness greater than 100 nm was tightly loaded onto the glass microbubbles. CTAB led to a slight expansion of the bandgap energy from 3.22 eV (TiO2(0)/GB) to 3.41 eV (TiO2(3.0)/GB). The ECB and the EVB values were −0.32 and 2.91 V for the TiO2(1.5)/GB, respectively. Both the average pore size (from 5.59 to 9.44 nm) and the total pore volume (from 0.0799 to 0.1283 cm3/g) of TiO2(C)/GB increased with an increasing amount of CTAB. The hole-electron recombination efficiency was in the sequence of TiO2(1.5)/GB< TiO2(3.0)/GB< TiO2(0)/GB. The AR1 degradation efficiency varied with the CTAB amount, and the maximum degradation efficiency was obtained for TiO2(1.5)/GB. The TiO2(C)/GB hollow powders were suspended in an AR1 solution during the degradation process, and TiO2(C)/GB floated on the water surface after treatment to ensure fast solid-water separation. The reaction rate constants were 1.79 × 10−2 and 1.21 × 10−2 min−1 for TiO2(1.5)/GB and the unsupported TiO2 powders, respectively. TiO2(1.5)/GB had a stronger activity than the TiO2 powders.

Supported TiO2 on Kaolin, Cordierite, and Calcite for Photocatalytic Removal of Dyes from Wastewater

AbstractKaolin, cordierite, and calcite are investigated as supports for TiO2. The prepared TiO2/support samples are examined for the removal of organic dyes from wastewater. The samples are preliminarily investigated to identify the optimal loaded system using synthetic wastewater containing methylene blue (MB). Data indicate that the investigated support significantly affects the photocatalytic activity of the supported TiO2. Low photocatalytic activity toward MB degradation is observed upon using TiO2/calcite when compared to the unsupported TiO2. Interaction between calcite and titania species probably occurrs to produce the less photoactive CaTiO3 amorphous species. Anatase TiO2 is obtained upon using kaolin and cordierite as supports. The low photocatalytic performance of the TiO2/kaolin sample is also observed. A high concentration of MB on TiO2/kaolin surfaces blocks the photoactive sites. TiO2/cordierite shows the highest photocatalytic activity compared to the unsupported TiO2 as well as the other TiO2/support samples. Rigid cordierite particles suppress the agglomeration of TiO2 particles during the preparation, leading to a high exposed surface of TiO2 towards light illumination. TiO2/cordierite is investigated for the removal of organic dye from real wastewater collected from a textile dyeing factory. Color removal of up to 46% is achieved upon UV irradiation.

Synthesis and characterization of Ag/TiO2/composite aerogel for enhanced adsorption and photo-catalytic degradation of toluene from the gas phase

Despite titanium dioxide has some remarkable properties as a photo-catalyst, its usage in the photo-catalysis processes is associated with several drawbacks, like high band gap energy and clumping of its particles. In this study, a composite aerogel was exploited as a support for titanium dioxide to prevent clump formation and increase the production of electron-hole pairs. The results revealed that both utilized nanoparticles, i.e. TiO2 and Ag, were uniformly dispersed on the surface of composite aerogel. The absorption region of the synthesized catalysts shifted to the visible region and, in fact, the additions of Ag to the composite aerogel reduce the band gap energy of TiO2 from 3.17 to 2.7 eV. Studies on the degradation of toluene in gas streams through a fluidized bed reactor showed that the photo-catalytic activity of TiO2 supported on the composite aerogel was much higher than that of the unsupported titanium dioxide, so that the degradation rates of toluene were 95.7% and 15%, respectively for supported and unsupported TiO2. The results indicated that the highest oxidation rate of toluene was obtained at 45% humidity. The Intermediate products formed during the degradation of toluene by the composite photo-catalyst were identified which were included formic acid, acetic acid, and benzaldehyde. Overall, the composite aerogel could be used as a useful support for the TiO2 catalyst, and the prepared photo-catalyst has a high potential to be used in the oxidation of toluene in gas-phase streams in industrial scale.

Anthocyanin-Sensitized TiO2 Nanoparticles for Phenazopyridine Photodegradation under Solar Simulated Light

Pharmaceutical wastes are emerging as water contaminants. Like other organic contaminants, it is necessary to find safe and economic methods to remove them from the water. In this work, anthocyanin was used as a natural dye sensitizer for the wide band gap nanosize rutile TiO2. The TiO2/Anthocyanin particles were supported on activated carbon particle surfaces. The resulting composite, which was prepared and characterized by different methods, was then used as a catalyst in the photodegradation of phenazopyridine (a model pharmaceutical contaminant) under a solar simulated light. Depending on experimental conditions, up to 90% of the contaminant was mineralized leaving no new organic products in the reaction mixture. The results show the feasibility of using the activated carbon-supported TiO2/Anthocyanin photocatalyst for pharmaceutical contaminant removal in water. The natural dye anthocyanin readily sensitized the TiO2 to visible light. The unsupported TiO2, with its nanosize particles, was not easy to recover by simple separation methods, while the activated carbon-supported catalyst was easily isolated by decantation after reaction cessation. Moreover, the recovered AC/TiO2 catalyst could also be regenerated by adding fresh anthocyanin sensitizer after recovery for further reuse. Keeping the contaminant molecules closer to the catalytic sites by adsorption, the support also enhanced the efficiency of photocatalyst.

Highly enhanced photocatalytic degradation of dye rhodamine B on the biogenic hierarchical porous TiO2/SiO2 with 1D/3D-chain

A hybrid photocatalyst consisting of TiO2 and nonporous SiO2 (TiO2/CS-RH) is prepared by loading TiO2 sol on one-dimensional/three-dimensional chain (1D/3D-chain) which is synthesized from rice husk. The products are characterized by X-ray diffraction, N2-adsorption–desorption analysis and scanning electron microscopy. Meanwhile, the corresponding photocatalytic activity is evaluated by measuring the photocatalytic oxidation of rhodamine B (RhB). The results reveal that TiO2/CS-RH displays a hierarchical porous structure from micrometer to nanometer scale with high BET surface area (574.7–719.4 cm2/g). Meanwhile, the activity of TiO2/CS-RH for the photocatalytic degradation of RhB in aqueous slurry is significantly higher than that of the unsupported TiO2. The optimal TiO2 loaded on the support was two times and then treated at 600 °C for 120 min to complete the conversion of RhB. In contrast, the unsupported TiO2 photocatalyst could convert only 20% of RhB in the same irradiation time and condition.

A simple and innovative route to remarkably enhance the photocatalytic performance of TiO2: Using micro-meso porous silica nanofibers as carrier to support highly-dispersed TiO2 nanoparticles

TiO2 nanoparticles/micro-meso porous silica nanofibers hybrid photocatalyst (TiO2/MMPSNF) was successfully synthesized by a simple and innovative sol-adhesion method. The composition, crystalline phase, microstructure and surface property of the as-prepared composite material were characterized. The results show that the TiO2/MMPSNF is composed of TiO2 and SiO2 with weight ratio of about 1:1.7. Micro-meso porous silica nanofibers (MMPSNF) is combined with TiO2 nanoparticles through Ti-O-Si bond, which effectively hinders the anatase-to-rutile phase transition and restrains the crystalline growth of TiO2. The microstructure of the TiO2/MMPSNF shows that the highly dispersed TiO2 nanoparticles are uniformly distributed on the surface of the MMPSNF to form a monolayer dispersion structure. The photocatalytic performances of as-prepared samples were evaluated through a series of kinetic tests on degradation of Rhodamine B (RhB). The results show that the TiO2/MMPSNF has much higher adsorption capacity and photocatalytic activity than that of the reference materials of unsupported sol-gel TiO2 and P25 TiO2 nanoparticles. According to the investigation, it is proposed that the MMPSNF can effectively enhance the photocatalytic activity of the hybrid photocatalyst by providing synergistic effect of a highly absorptive substrate and a nano-scaled supporter.

The influence of zeolites fly ash bead/TiO2 composite material surface morphologies on their adsorption and photocatalytic performance

A low cost zeolite fly ash bead/TiO2 (ZFABT) composite materials with various surface structure features were prepared for describing those structures importance on TiO2 coating, adsorbability and photocatalytic performances. The results indicated that fly ash bead (FAB) surface was significantly altered by the precipitation/growth of secondary zeolite phases after alkali activation, which generates abundant open pores and stacked petal-liked spherical beads (∼2μm, Sodalite zeolites). More importantly, this porosity increases as activation time was increased from 2h to 12h, through the precipitation of sodalite and then Na-P1 (lamellar crystals) and Na-X (octahedral crystals) zeolite structures. Compared to those of unsupported TiO2 or inactivated support/TiO2 samples, all of ZFABT samples exhibited a higher adsorption capacity and photocatalytic efficiency for RhB removal. However, adsorption is not only one factor to influence TiO2 surface reaction, the intraparticle diffusion rate of rhodamine B (RhB) molecules, and light penetration are also important parameters. Alkali activated 4h ZFABT sample exhibited the highest photocatalytic activity, indicating its pore structure provided a better balance for those parameters to achieve a synergistic adsorption/photocatalytic process. The kinetics model suggested its high intraparticle diffusion rate allowed for more RhB molecules to easily reach the reaction surface, which is more important for high efficiency photocatalysis.

The effect of Pt nanoparticles distribution on the removal of cyanide by TiO2 coated Al-MCM-41 in blue light exposure

With an aim to enhance the photocatalytic activity, Pt loaded TiO2–Al-MCM-41 catalysts with high surface area were synthesized by a multistep route. The waste of the rice processing, rice husk (RH), was used as the precursor for the extraction of silica. The diffuse reflectance and photoluminescence spectroscopy revealed the extension of the absorption edge in the visible region and exciton trapping nature of the dispersed platinum. The structural analysis was carried out by XRD, whereas X-ray photoelectron spectroscopy identified the chemical states of the components of the synthesized powders. The BET surface area measurements revealed the reduction in the surface area and pore volume with the increasing platinum loading. TEM micrographs showed the uniform distribution of TiO2 and Pt nanoparticles at the surface of Al-MCM-41. The photocatalytic efficiency of the synthesized powders as photocatalysts was obtained for the removal of 100ppm CN− from aqueous solution in fluorescent blue light exposure. Compared to unsupported TiO2, the Pt-loaded catalysts exhibited substantially high activity for the removal of CN−. A plausible mechanism for the removal of cyanide ions was proposed. The catalysts showed excellent stability and reproducibility in the successive use.

Computational Studies of the Interaction of Carbon Dioxide with Graphene-Supported Titanium Dioxide

The interaction of carbon dioxide (CO2) with titanium dioxide (TiO2) supported on graphene (GR) and epoxy-enhanced graphene (GR-O) was investigated using density functional theory (DFT) calculations and compared with the interaction on unsupported TiO2 systems. Adsorption energies, charge density differences, and activation barriers were calculated. TiO2 clusters, comprising two to four TiO2 units were considered. We show that the carbon support influences the binding energy of CO2 significantly when chemisorbed, and the molecule is bound in a bent configuration. The epoxy oxygen connection of GR-O with TiO2 leads to a further increase in the binding energy of CO2, as does increasing the size of the TiO2 cluster, due to a higher charge delocalization on the GR sheet.

Photodegradation of Herbicide Dicamba with TiO2 Immobilized on HZSM-11 Zeolite

Photodegradation of dicamba, an ionizable herbicide, using TiO2 supported on HZSM-11 zeolite was investigated. Four photocatalysts with different weight percentages (wt%) of TiO2 were evaluated: 3%, 10%, 30% and 50%. The effects of the catalyst concentration, the initial pH value and the repeatability of the photocatalytic activity after multiple cycles of reuse were also evaluated. Results showed complete degradation of dicamba within 120 min with the TiO2/HZSM-11 (30 wt%) catalyst. Also, this catalyst is stable (no detectable leaching was observed), can be easily removed from treated solutions and it is reusable for at least nine consecutive cycles. An XRD analysis indicated that the TiO2/HZSM-11(30%) catalyst remained unchanged until the ninth cycle, when it was compared with a new catalyst. The results indicated that the addition of H2O2 to the solution did not affect the catalyst structure.These are important advantages over unsupported TiO2, making it a good photocatalyst for the treatment of water courses polluted with dicamba.

Photocatalytic decolorization of reactive red 198 dye by a TiO2–activated carbon nano-composite derived from the sol–gel method

In this research, a TiO2–activated carbon nano-composite was prepared by a sol–gel method and characterized by XRD, FE-SEM, EDS, FTIR, BET surface area, photoluminescence spectroscopy and UV–Vis diffuse reflectance spectroscopy. The photocatalytic activity of the nano-composite was evaluated through degradation of reactive red 198 (RR 198) under UV light, and was compared to unsupported TiO2. The XRD result indicated that the TiO2 nano-composite contained only anatase phase. The surface area of the TiO2 increased from 48 to 100 m2/g through the fabrication of the nano-composite. The photocatalytic results indicated that the RR 198 was decolorized around 42 and 38 % during a 210-min irradiation period in the presence of nano-composite and TiO2, respectively. It means that nano-composite enhanced the photocatalytic activity of the TiO2 nano-particles. After 20 h of irradiation in the presence of the nano-composite, 97 % of RR 198 had degraded.

Enhanced photocatalytic properties of core@shell SiO2@TiO2 nanoparticles

SiO2@TiO2 core@shell nanoparticles (CSNs) have recently attracted great attention due to their unique and tunable optical and photocatalytic properties and higher dispersion of the supported TiO2. Thus, development of facile, reproducible and effective methods for the synthesis of SiO2@TiO2 CSNs and a fundamental understanding of their improved properties, derived from combination of different core and shell materials, is of great importance. Here we report a very facile and reproducible method for the synthesis of CSNs with a control of particle morphology, crystallinity and phase selectivity, and provide important insight into the effect of core@shell configuration on the photocatalytic and optical properties of SiO2@TiO2 CSNs. For this purpose, synthesis of highly dispersed anatase nanocrystals (∼5nm) of high surface area was carried out by supporting these nanocrystals on silica sub-micron spheres in the form of a porous shell of controlled thickness (10–30nm). The amorphous TiO2 shell was crystallized into anatase using a low temperature (105°C) hydrothermal treatment. The resulting CSNs were characterized by scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, x-ray photoelectron spectroscopy, X-ray diffraction, vibrational spectroscopy, zeta-potential measurements, BET surface area and electron paramagnetic resonance measurements. Both experimental data and theoretical simulations showed that due to the size of the complete particle (SiO2@TiO2), the general optical response of the system is regulated by Rayleigh scattering, exhibiting a red-shift of the extinction spectra as shell-thickness increases. The SiO2@TiO2 configuration leads to efficient light harvesting by increasing the optical path inside the core@shell particles. An enhanced photoactivity and good recyclability of SiO2@TiO2 CSNs was demonstrated compared to unsupported TiO2. Together with BET surface area measurements, direct assessment of the density of photocatalytic sites probed by electron paramagnetic resonance measurements was used to provide insight into the enhanced photocatalytic activity of CSNs, which is also understood as a consequence of Rayleigh scattering, relative enhancement of the adsorption of organic molecules on the core@shell photocatalyst surface and increased optical path inside the SiO2@TiO2 particles. All these aspects are directly influenced by the core@shell configuration of SiO2@TiO2 samples.

Improved photoelectrical performance of graphene supported highly crystallized anatase TiO2

In this study, titanium oxysulfate (TiOSO4) and graphene were used as titanium source and supporter, respectively, to synthesize anatase TiO2-graphene (TiO2-G) composite. Crystal structure, morphology, and composition of TiO2-G were investigated by X-ray diffraction, scanning electron microscope, transmission electron microscope, and thermogravimetric analysis. Both TiO2-G and blank TiO2 powders exhibit spindle-shaped structure with the long axis along [001]. Compared to unsupported TiO2, TiO2 nanoparticles uniformly formed on graphene surface. When fabricated into dye-sensitized solar cells, photoelectrical conversion efficiency of TiO2-G (2.3 %) was much higher than that of blank TiO2 (0.89 %) prepared at the same conditions. Moreover, high sintering temperature enhanced photoelectrical performance of the composite. When the temperature was increased from 450 to 600 °C, the efficiency was improved from 1.5 to 2.6 %. The findings above demonstrate that TiO2-G has great potential for applications in dye-sensitized solar cells.

Enhanced photocatalytic activity of TiO2@mercapto-functionalized silica toward colored organic dyes

Core-shell-type TiO2@mercaptopropyl-func- tionalized silica (MPS) particles were prepared for enhanced photocatalytic performance of TiO2. The MPS particles were adopted in the composite-type photocatalyst design so as to enhance the photo-catalytic activity through the chemical interaction between chemically modified substrate particles and organic dye molecules, although they do not have photocatalytic activity. Three organic dyes, rhodamine B, rhodamine 6G, and methyl orange, were selected for testing dye adsorption characteristics and photocatalytic activities of the TiO2@MPS particles, commercial P25, and unsupported TiO2 nanosols. Rhoda- mine B and rhodamine 6G dyes were adsorbed much more