Pure Anatase TiO2 Research Articles

Continuous ultrasonic stimulation based direct green synthesis of pure anatase-TiO2 nanoparticles with better separability and reusability for photocatalytic water decontamination

Titanium dioxide nanoparticles have shown a tremendous potential in various fields such as photocatalysis, solar-photovoltaics, electrodes, sensors, implants and pigments. Due to these versatile applications, their synthesis routes have gained a vast attraction and demand for being frugal and eco-friendly with better control over the anatase and rutile phase ratio. Comprehensively, the sol-gel method is a widely used technique for the synthesis of TiO2 nanoparticles that requires several additional chemical entities such as organic solvents, acids and capping agents. It makes this process quite uneconomical and hazardous in nature. In the present study, non-hazardous microwave and/or ultrasound based one-pot synthesis approaches have been studied for the production of phase controlled TiO2 nanoparticles and compared with the sol-gel synthesized and commercially available TiO2 nanoparticles. These comparisons have been validated through several material characterization techniques. The obtained results have shown that the ultrasound based synthesis followed by suitable thermal processing alone has tremendous potential to produce phase controlled TiO2 nanoparticles (preferably anatase phase), mostly in the form of nano-micro aggregates. In addition, the photocatalytic activity of ultrasonically synthesized TiO2 nanoparticles has also been examined and compared with that of the commercially available TiO2 nanoparticles. It is interesting to observe that, ultrasonically synthesized TiO2 nanoparticles have not only shown improvised photocatalytic degradation activity, but also shown a significant improvement on their separability and recyclability for water treatment applications, in comparison to that of the commercially available TiO2 nanoparticles (TiO2-P25).

Facile synthesis of core–shell-structured rutile TiO2 with enhanced photocatalytic properties

Abstract Titanium oxide (TiO2) has received growing attention in photocatalyst is owing to its chemical stability and ecofriendly nature. Among the different phases of TiO2, pure anatase and mixed-phase TiO2 (Degussa P25) have been recognized as superior photocatalysts. Indeed, the mechanism of photocatalysis and the roles of various parameters in the process have been well documented for pure anatase TiO2 and Degussa P25. However, the pure rutile phase remains unexplored in the context of photocatalytic applications. Thus, herein, we report a one-pot method to modify the surface of pure rutile TiO2 and examine the factors that affect its photocatalytic performance. This modification was achieved by treating rutile TiO2 with H2O2 under microwave irradiation, which led to the formation of core-shell rutile TiO2 with a crystalline core and an amorphous shell bearing Ti3+ and Ti–OH species on the surface. The photocatalytic performance of this modified TiO2 species was enhanced threefold compared with that of unmodified rutile TiO2. This basic understanding of how to improve the photocatalytic performance of rutile phase TiO2 will play a crucial role in enhancing the catalytic performance of other metal oxides.

A comparative study on the influence of pure anatase and Degussa-P25 TiO2 nanomaterials on the structural and optical properties of dye sensitized solar cell (DSSC) photoanode

In this paper, two different nanomaterials of pure anatase and Degussa-P25 TiO2 based dye sensitized solar cells (DSSCs) photoanode were fabricated and characterized to investigate the influence of the nanomaterials and the natural dye on various optical and structural parameters of the photoanodes. Adsorption of dye showed remarkable changes on the various structural parameters including crystallite size, strain, morphology index (MI), specific surface area (SSA), dislocation density, and crystallites per unit surface area (CPSA) for both the Degussa-P25 and pure anatase TiO2 samples analysed by X-ray diffraction (XRD). In UV–vis-NIR spectroscopic optical studies for the dye-adsorbed samples, the overall light absorption was found to decrease for both the anatase and Degussa-P25 from UV to NIR. On the other hand, the dye-free samples were found to exhibit a lower light absorption from UV to green and beyond that level, absorption showed higher value than the dye adsorbed samples. Among the dye-free and dye-adsorbed samples, absorption depth was observed to increase more with the increasingly incident light wavelength for all the dye-adsorbed than the dye-free samples. Optical band gaps were found to decrease from 3.1 eV to 2.95 eV and 3 eV to 2.83 eV for dye-free and dye-adsorbed samples of Degussa-P25 and pure anatase, respectively.

Fabrication of Hydrophobic Indonesia Bamboo Modified by Octa Fluoro 1-Pentanol (OFP) Based on TiO2 Thin Film for Self-cleaning Application

The ultra-hydrophobic surface on Indonesia bamboo timber has been successfully prepared using OFP (2,2,3,3,4,4,5,5-octafluoro-1-pentanol) as a modifier agent. The hydrothermal method has been used to fabricate anatase TiO 2 film followed by OFP modification. Maximal water contact angle of 123 ο has been obtained for the composition of 10 mL of OFP and 15 mL of 2-propanol (B-T-OFP10). XRD analysis showed the existence of pure anatase TiO 2 film on bamboo timber, confirmed by EDS result. SEM image of a TiO 2 -coated and a typical ultra-hydrophobic bamboo timber revealed irregular aggregates of spherical TiO 2 on the surface and compact ultra-hydrophobic surface, respectively. The optimum sample (B-T-OFP10) showed excellent mechanical stability, self-cleaning property, and flame retardancy compared to pure bamboo timber.

First-principles study of Mn-S codoped anatase TiO2

In this work, the CASTEP program in Materials Studio 2017 software package was applied to calculate the electronic structures and optical properties of pure anatase TiO2, S-doped, Mn-doped and Mn-S co-doped anatase TiO2 by GGA + U methods based on the density function theory (DFT). The results indicate that the lattice is distorted and the lattice constant is reduce due to doping. The doping also introduces impurity energy levels into the forbidden band. After substitution of Mn for Ti atom, band gap narrowing of anatase TiO2 is caused by the impurity energy levels appearance in the near Fermi surface, which are contributed by Mn-3d orbital, Ti-3d orbital and O-2p orbital hybridization. After substitution of S for O atom, band gap narrowing is creited with the shallow accepter level under the conduction hand of S-3p orbital. The Mn-S co-doped anatase TiO2 could be a potential candidate for a photocatalyst because of tis enhanced absorption ability of visible light. The results can well explain the immanent cause of a band gap narrowing as well as a red shift in the spectrum for doped anatase TiO2.

Preparation of anatase TiO2 nanoparticles using low hydrothermal temperature for dye-sensitized solar cell

One device being developed as an alternative source of renewable energy by utilizing solar energy source is dye-sensitized solar cells (DSSC). This device works using simple photosynthetic-electrochemical principle in the molecular level. In this device, the inorganic oxide semiconductor of titanium dioxide (TiO2) has a great potential for the absorption of the photon energy from the solar energy source, especially in the form of TiO2 nanoparticle structure. This nanoparticle structure is expected to improve the performance of DSSC because the surface area to weight ratio of this nanostructures is very large. In this study, the synthesis of TiO2 nanoparticle from its precursors has been performed along with the fabrication of the DSSC device. Effort to improve the size of nanocrystalline anatase TiO2 was accomplished by low hydrothermal treatment at various temperatures whereas the crystallinity of the anatase phase in the structure was performed by calcination process. Characterization of the materials was performed using X-ray Diffraction (XRD) and scanning electron microscope (SEM), while the DSSC performance was examined through a high precision current versus voltage (I-V) curve analyzer. The results showed that pure anatase TiO2 nanoparticles could be obtained at low hydrothermal of 100, 125, and 150 °C followed by calcination at 450 °C. The best performance of photocurrent-voltage characteristic was given by TiO2 hydrothermally synthesized at 150 °C with power conversion efficiency (PCE) of 4.40 %, whereas the standard TiO2 nanoparticles has PCE only 4.02 %. This result is very promising in terms low temperature and thus low cost of anatase TiO2 semiconductor preparation for DSSC application.

Influence of inorganic additives on the photocatalytic removal of nitric oxide and on the charge carrier dynamics of TiO2 powders

Building materials employing TiO2 as photocatalyst usually contain several additives. The interplay of the additives and the photocatalytic NO degradation has been rarely investigated, although it is of utmost importance for the design of new highly active materials. Hence, in the present study the effects of such additives (BaSO4, CaCO3, and Na2CO3) on the photocatalytic activity and on the charge carrier dynamics have been evaluated. The degradation of nitric oxide (NO) was studied employing a standardized photocatalytic activity test (ISO 22197-1) and the charge carrier kinetics were observed by transient absorption spectroscopy. TiO2-additive powder samples were obtained by grinding pure anatase TiO2 with a single additive with varying volume composition. Overall, the obtained apparent quantum yields of the samples correlated well with the charge carrier concentration. Moreover, BaSO4 has proven its chemically inert character. However, the optical properties of the powder samples containing BaSO4 lead to relatively high photonic efficiencies even with low TiO2 content. TiO2-BaSO4 samples with only 25% TiO2 showed nearly the same quantum yield for the NO degradation as the pure photocatalyst. The reason for the high photocatalytic activity is the strong absorption of UV-light caused by the scattering inside the powder samples. The charge carrier kinetics of TiO2 after the addition of Na2CO3 and CaCO3 revealed two different chemical effects of the additives. Na2CO3 reduced the apparent quantum yield of the TiO2 samples due to the fast recombination of charge carriers (identified by a fractal kinetics fit). On the other hand, the presence of CaCO3 had a beneficial influence on the stabilization of trapped charge carriers in TiO2.

The low temperature selective oxidation of H2S to elemental sulfur on TiO2 supported V2O5 catalysts

The selective oxidation of H2S to elemental sulfur at low temperature (130 °C) was investigated on various TiO2-supported vanadium oxide catalysts. The TiO2 supports were commercially available pure anatase TiO2 (dXRD 21 and 43 nm with specific surface area 63 and 10 m2/g, respectively), solvothermal-synthesized pure anatase TiO2 (dXRD 15 nm, 69 m2/g), P-25 TiO2 (mixed anatase/rutile phase, 46 m2/g), and rutile TiO2 (dXRD 40 nm, 6 m2/g). In order to obtain high catalytic activity of the V2O5/TiO2 catalysts, a combination of highly dispersed vanadium oxides and a strong interaction of V-Ti species were found to be necessary. As revealed by the XPS, Raman, and O2-TPD results, the interaction between active V component and TiO2 support was shown by the presence of partially reduced V-Ti species. Due to the strong interaction between V and TiO2 support, the active V component, which was not fully oxidized, led to more oxygen vacancies being formed and facilitated a rapid catalyst regeneration from V4+ to V5+ (re-oxidation). Hence, the capability of the catalysts for H2S removal was greatly enhanced. Among them, the V2O5 supported on anatase TiO2 with dXRD 21 nm exhibited the best catalyst performances using the feed molar ratio (O2/H2S) of 0.5.

Rutile versus anatase for quantum dot sensitized solar cell

In this paper, we report comparative studies of CdS/CdSe quantum dot sensitized solar cell (QDSSC) using the phase pure anatase and rutile TiO2 nanocrystals as the photoanode materials, which were prepared through a controlled hydrolysis route. Photovoltaic performance investigations demonstrate that the QDSSC made from rutile TiO2 (R-QDSSC) achieved higher shot-circuit photocurrent density (Jsc) and open-circuit photovoltage (Voc), which leads to a higher power conversion efficiency compared to the cell made from anatase TiO2 (A-QDSSC). Our systematic studies have shown that the use of rutile TiO2 to fabricate QDSSC offers two advantages over anatase TiO2: (1) rutile is more favorable for the growth of CdS/CdSe QDs that leads to the enhancement of light harvesting. (2) rutile is of advantage to inhibit the charge recombination and improve electron injection from QDs to TiO2, ascribable to its superior ability to lower the surface/interface defects in photoanode film together with the larger conduction band offset between QD and rutile TiO2.

Solution Plasma Process-Derived Defect-Induced Heterophase Anatase/Brookite TiO2 Nanocrystals for Enhanced Gaseous Photocatalytic Performance.

We report a simple room-temperature synthesis route for increasing the reactivity of a TiO2 photocatalyst using a solution plasma process (SPP). Hydrogen radicals generated from the SPP chamber interact with the TiO2 photocatalyst feedstock, transforming its crystalline phase and introducing oxygen vacancy defects. In this work, we examined a pure anatase TiO2 as a model feedstock because of its photocatalytic attributes and well-characterized properties. After the SPP treatment, the pure anatase crystalline phase was transformed to an anatase/brookite heterocrystalline phase with oxygen vacancies. Furthermore, the SPP treatment promoted the absorption of both UV and visible light by TiO2. As a result, TiO2 treated by the SPP for 3 h showed a high gaseous photocatalytic performance (91.1%) for acetaldehyde degradation to CO2 compared with the activity of untreated TiO2 (51%). The SPP-treated TiO2 was also more active than nitrogen-doped TiO2 driven by visible light (66%). The overall photocatalytic performance was related to the SPP treatment time. The SPP technique could be used to enhance the activity of readily available feedstocks with a short processing time. These results demonstrate the potential of this method for modifying narrow-band gap metal oxides, metal sulfides, and polymer composite-based catalyst materials. The modifications of these materials are not limited to photocatalysts and could be used in a wide range of energy and environment-based applications.

One-step hydrothermal synthesis of titanium dioxide decorated on reduced graphene oxide for dye-sensitised solar cells application

Dye-sensitised solar cells (DSSCs) are one of the promising prospects for efficient renewable resources. To bring DSSCs to the point of commercial readiness and viability in terms of performance and cost, substantial research on the development of a high efficiency DSSCs system is necessary. Our recent studies have indicated that a maximum conductivity of 29.1 μS/cm and conversion efficiency of 4.76% under 1.5 AM condition was successfully achieved from 0.2 wt% TiO2 loaded on reduced graphene oxide (rGO) forming a nanocomposite film, which is approximately twice or three times higher than that of pure rGO nanosheets and anatase TiO2 film. The findings were mainly attributed to the fact that rGO nanosheets could further increase the photo-induced electron transportation rate and minimise the recombination losses within the TiO2 lattice in this binary hybrid photoelectrode.

Electronic and optical performances of (Cu, N) codoped TiO<sub>2</sub>/MoS<sub>2</sub> heterostructure photocatalyst: Hybrid DFT (HSE06) study

Anatase titanium dioxide (TiO<sub>2</sub>) has attracted much attention due to its excellent photocatalytic properties. However, the band gap of anatase TiO<sub>2</sub> is 3.2 eV, which can absorb only about 4% of the ultraviolet light (<i>λ</i> < 400 nm). Molybdenum disulfide (MoS<sub>2</sub>) is a new layered two-dimensional compound semiconductor, and it has been widely studied for its preferably optical absorption and photocatalytic properties. Moreover, the high recombination rate of photoexcited electron-hole of monolayer MoS<sub>2</sub> leads to low photocatalytic efficiency. In this work, based on Heyd-Scuseria-Ernzerhof (HSE06) hybrid density functional theory, the geometric structure, electronic structure, optical properties, charge transfer and effect of pressure on structure of Cu/N doped TiO<sub>2</sub>/MoS<sub>2</sub> heterostructures are systematically studied. The interface interaction between anatase TiO<sub>2</sub>(101) surface and monolayer MoS<sub>2</sub> shows that TiO<sub>2</sub> and MoS<sub>2</sub> form a van der Waals heterostructure. The defect formation energy is calculated to demonstrate that Cu@O&N@O is the most stable codoping site. The result of the density of states shows that the band gap of TiO<sub>2</sub>/MoS<sub>2</sub> heterojunction is 1.38 eV, which is obviously smaller than that of the pure anatase TiO<sub>2</sub>(101) surface (2.90 eV). The band gap of Cu/N doped TiO<sub>2</sub>/MoS<sub>2</sub> heterojunction obviously decreases, and an impurity band provided by Cu 3d orbitals appears in the forbidden band, which leads to the decrease of the photon excitation energy and the enhancement of the optical absorption capacity. The <i>x-y</i> planar averaged and three-dimensional charge density difference of Cu/N doped TiO<sub>2</sub>/MoS<sub>2</sub> are also calculated. It is found that there are electrons' and holes' accumulation in the doped anatase TiO<sub>2</sub>(101) surface and the single layer MoS<sub>2</sub>, showing that the Cu/N doping can effectively reduce the recombination of the photoexcited electron hole pairs. Calculated optical absorption spectra show that Cu/N doped TiO<sub>2</sub>/MoS<sub>2</sub> system has obvious improvement in the absorption of visible light. In addition, we calculate the geometrical, electronic and optical absorption spectra of TiO<sub>2</sub>/MoS<sub>2</sub> heterojunction under different pressures. The results show that the appropriate increase of pressure can effectively improve the optical absorption properties of heterojunction and Cu/N doped TiO<sub>2</sub>/MoS<sub>2</sub> heterojunction and TiO<sub>2</sub>/MoS<sub>2</sub> heterojunction can effectively improve the optical properties of the material. These findings are helpful in understanding the photocatalytic mechanism and relevant experimental observations.

Titania Nanobelts as a Scattering Layer with Cu2ZnSnS4 as a Counter Electrode for DSSC with Improved Efficiency

Various nanostructures of Titania (TiO2) play a significant role in the performance of dye sensitized solar cells (DSSCs) and affect the overall light harvesting efficiency of the cells. In this article we present the one dimensional nanostructure of TiO2(nanobelts) can increase the light scattering effect, light harvesting effect and electron transport in the DSSC to improve its performance. Pure anatase TiO2 nanobelts were synthesized by a hydrothermal method using commercial material (P25) and characterized by XRD and SEM. Cu2ZnSnS4 (CZTS) nanoparticles have been prepared by thermal decomposition method used as counter electrode material instead of platinum. DSSC have been fabricated by using a new type of double layered photoanode, which was prepared and optimized by using TiO2 nanoparticles as the main layer and TiO2 nanobelts as the over-layer (scattering layer). The photoelectric conversion efficiency (PCE) of the prepared cells was measured by solar simulator under 1 sun illumination (100 mW/cm2, AM 1.5). The DSSCs with CZTS nanoparticles based counter electrodes without scattering layer relatively low PCE of 5.76 %. However, the PCE was clearly improved with scattering layer and a maximum PCE of 7.85% was achieved.

Supercritical CO2-assisted deposition of NiO on (101)-anatase-TiO2 for efficient facet engineered photocatalysts

Deposition of NiO on the (101) facet of anatase nanocrystals by the SFCD route yields nanocomposites more efficient than pure anatase TiO2 for the photodecomposition of both anionic and cationic dyes.

Antimicrobial activity of ZnO-TiO2 nanomaterials synthesized from three different precursors of ZnO: influence of ZnO/TiO2 weight ratio

In this study, ZnO-TiO2 nanoparticles were synthesized from three different precursors for ZnO (zinc acetate di-hydrate, zinc nitrate hexahydrate and zinc sulfate heptahydrate) and titanium (IV) isopropoxide for TiO2. The prepared nanomaterials were calcined at 500 °C for 3 h and characterized by various physicochemical techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy, combined with energy dispersive X-ray spectroscopy (TEM-EDS). The obtained results showed that the crystalline structure, size and morphology of the ZnO-TiO2 nanoparticles are strongly influenced by the nature of the precursor of ZnO, as well as the ZnO/TiO2 weight ratio. The antibacterial and antifungal activities of the synthesized nanomaterials were evaluated, in the dark, against five multi-resistant of Gram positive (Staphylococcus aureus) and Gram negative (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Salmonella Paratyphi A) bacteria and a fungus (Candida albicans), which are pathogenic for humans. The obtained results showed that pure TiO2 anatase is inactive against the tested strains, while the addition of ZnO to TiO2 improves noticeably the effectiveness of TiO2 nanoparticles, depending on the nature of the precursor of ZnO and the ZnO/TiO2 weight ratio.

Characterization and Computation of Yb/TiO₂ and Its Photocatalytic Degradation with Benzohydroxamic Acid.

Yb-doped TiO2 (Yb/TiO2) compositions were synthesized by sol-gel method, and the prepared materials were characterized by X-ray Diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-visible diffuse-reflectance spectrum (UV-Vis DRS), transmission electron microscope (TEM) and high resolution transmission electron microscope (HRTEM), energy dispersive spectrometer (EDS), and N2 adsorption. A beneficiation reagent of benzohydroxamic acid (BHA) was used to test the photocatalytic activity of Yb/TiO2. The characterizations indicate that the doping of Yb could inhibit the crystal growth of TiO2, enhance the specific surface area, increase the binding energy of Ti2p, and also slightly expand the adsorption ranges to visible light. Furthermore, the computation of band structure also indicates that Yb-doped TiO2 could make the forbidden band narrower than pure anatase TiO2, which presents a red shift in the absorption spectrum. As a result of the photodegradation experiment on BHA, Yb/TiO2 (0.50% in mass) sintered at 450 °C displayed the highest catalytic activity for BHA when compared with pure TiO2 or other doped Yb/TiO2 compositions, and more than 89.2% of the total organic carbon was removed after 120 min. Almost all anions, including Cl−, HCO3−, NO3−, and SO42−, inhibited the degradation of BHA by Yb/TiO2, and their inhibition effects followed the order of HCO3− > NO3− > SO42− > Cl−. Cations of Na+, K+, Ca2+, and Mg2+ displayed a slight suppressing effect due to the impact of Cl− coexisting in the solution. In addition, Yb/TiO2 maintained a high photocatalytic ability with respect to BHA after four runs. It is hypothesized that ·OH is one of the main species involved in the photodegradation of BHA, and the mutual transformation of Yb3+ and Yb2+ could promote the separation of electron-hole pairs.

Preparation and characterization of metals supported on nanostructured TiO2 hollow spheres for production of hydrogen via photocatalytic reforming of glycerol

Nanostructured TiO2 hollow spheres (THS) were prepared via a simple hydrothermal method with titanium butoxide, ethanol, urea, and ammonium sulphate. The effects of Ti/ethanol, and reflux temperature on the morphological properties of the nanostructured THS were investigated. An impregnation method was subsequently employed to load metals such as Cu, Co, Cr, Ag, and Ni on the optimized THS, followed by calcination in H2/N2 at 450°C for 4h. The morphological properties of the prepared samples were characterized by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and ultraviolet-visible spectroscopy (UV/vis). The SEM and TEM pictures showed that the Ti/ethanol ratio of 1:10 resulted in the formation of uniform hollow spheres. The XRD spectre revealed that phase transformation took place as the reflux temperature was increased, with pure anatase TiO2 hollow spheres being formed at 200°C. The BET surface areas of the calcined photocatalysts were in the range of 80.6–116m2/g−1. The UV/vis spectra of the photocatalysts showed that loading of transition metals reduced the band gap of the THS. The activities of the prepared catalysts were tested for hydrogen production via photocatalytic reforming of glycerol under solar irradiation. The improved hydrogen evolution from photocatalytic reforming of glycerol was attributed to: the high surface area which enhanced the adsorption of glycerol onto the surface of photocatalysts; high crystallinity and the reduced band gap which improved the solar light harvesting; the hollow chamber within the TiO2 spheres which produced multiple reflection of the light harvested, thus producing efficient electron/hole pair formation; and the detailed composition of the solids retarded the electron/hole recombination by trapping the electrons generated during the photo excitation of the photocatalysts, and thereby promoted their activity.

Ab initio study of electronic and optical properties of [formula omitted] doped anatase [formula omitted] (1 0 1) surface

In this paper we investigated the effects of Fe -doping of the anatase TiO2 (1 0 1) surface on the crystal structure, electronic and optical properties, and impurity formation energy by means of density functional theory (DFT). The calculations were performed by the SIESTA DFT code and were carried out by using Troullier-Martins pseudopotentials for the 12-electron valence configuration (3s23p63d24s2) of Ti atom, 6-electron valence configuration (2s22p4) of O atom and 8-electron valence configuration (3d64s2) of Fe atom. We used a double- ζ basis set including polarization functions. All calculations were spin-polarized. The mechanism of narrowing the band gap and increasing the photocatalytic activity in the visible light region, of the doped TiO2 is discussed by investigating the density of state. The band gap decreases as the concentration of the dopant increases. The Partial Density of States (PDOS) is not the same in the case of spin-up state or spin-down state. Enhanced optical absorption, for light polarized in the z direction (parallel to the surface normal) is clearly observed for Fe doped as compared to the pure anatase TiO2 and the optical absorption is found to increase with the increase in the Fe concentration. The DFT results indicate that the source of the increasing photocatalytic activity in the visible light region of the Fe doped material is due to the introduction of additional electronic states within the band gap.Since the Fe atoms are more stable in Ti substitutional lattice positions for the entire range of Fermi energy EF over the band gap, only this substitutional position is considered.We hope that our results will highlight a route to improved electronic and optical properties of anatase TiO2 for industrial applications.

TiO2 synthesized by various routes and its role on environmental remediation and alternate energy production

Researchers debate on if it is only the crystalline properties of TiO2 or also the surface morphology and even optical properties of different types of TiO2 are the instrumental parameters on photocatalysis. It is a subject of exploration whether the phase pure anatase TiO2 or the heterojunctions and band alignment in the two polymorphs of TiO2(anatase and rutile) plays the determining role in efficacy of a photocatalytic reaction. Three different synthetic routes such as polymerizable sol–gel, solution combustion and customized microwave assisted hydrothermal method have been employed to synthesize TiO2. The materials are characterized systematically using XRD, FE-SEM, HR-TEM, diffuse reflectance, photoluminescence, BET surface area and Raman spectroscopy. It is found that TiO2 synthesized by polymerizable sol–gel approach yields a mixed phase of anatase and rutile, while the other two approaches yield phase pure anatase. The band gap obtained from diffuse reflectance measurements are compared with the direct and indirect band gaps derived from Kubelka–Munk plots. Among the three synthetic routes, TiO2 synthesized by customized microwave assisted hydrothermal method exhibits the highest surface area, pore volume and diameter, and lowest recombination, which in turn play a crucial role in high rate of photocatalytic degradation of methylene blue. On the other hand, the phase pure anatase made out of solution combustion route with moderate surface area, pore volume and diameter outperformed the rest two catalysts in photocatalytic hydrogen production. The different reaction specific photocatalytic efficacies of these two materials are discussed with respect to the combinatorial role of nano-crystallinity, surface properties, and optical properties.

Elaboration and Enhanced Activity of the Mixed Oxide Zr x Ti 1 - x O 2 Nano-photocatalyst

The photocatalysis activity of mixed nanocomposite ZrxTi1-xO2 catalyst was studied. The catalysts with x=0, 0.1 and 0.2 were prepared via sol-gel method in a reactor with rapid micromixing using titanium tetra- isopropoxide and zirconium tetra-propoxide precursors and n-propanol solvent. The colloids were coated on cleaned borosilicate beads and treated at temperatures in the range between 400 and 600 °C to achieve crystalline anatase phase. The prepared materials were characterized by ICP-OES, BET, TDA and optical absorption measurements. The photocatalytic experiments were carried out in a continuous-flow fixed bed reactor on the gaseous ethylene decomposing. The photocatalytic activity of the prepared material was depended on the elemental compositions and calcination temperature. The enhanced activity, 50% higher compared to pure anatase TiO2, was obtained in the material containing 10 mol% Zr and thermally treated at 500 °C.