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TiO 2 -encapsulated H-ZSM photocatalysts were prepared by physical mixing of TiO 2 and zeolites. Pt was immobilized on the surface of the TiO 2 -encapsulated zeolite (H-ZSM) catalysts by a simple photochemical reduction method. Different weight ratios of both TiO 2 and Pt were hybridized with H-ZSM and the catalytic performance of the prepared catalysts was investigated for 2-propanol oxidation in liquid phase and acetaldehyde in gas phase reaction. Around 5–10 wt% TiO 2 -encapsulated H-ZSM catalysts was found to be optimal amount for the effective oxidation of the organics. Prior to light irradiation, Pt-TiO 2 -H-ZSM showed considerable amount of catalytic degradation of 2-propanol in the dark, forming acetone as an intermediate. In this study, Pt has played a major and important role on the total oxidation of 2-propanol as well as acetaldehyde. As a result, no residual organics were present in the pores of the zeolites. The catalysts could be reused more than three times without losing their catalytic activity in both phases. The Pt-TiO 2 -H-ZSM photocatalysts could overcome the problem of strong adsorption of organics in the zeolite pores (after the reaction). Thus, Pt-TiO 2 -H-ZSM can be used as a potential catalyst for both liquid and gas phase oxidation of organic pollutants. [ABSTRACT FROM AUTHOR]

Abstract: Nano-size TiO2 photocatalysts were prepared by sol-gel and ultrasonic-assisted sol-gel methods using two different sources of ultrasonicator, i.e., a bath type and tip type. The physicochemical characteristics of the catalysts were investigated by BET, XRD and TEM analyses and the photocatalytic properties of the TiO2 catalysts prepared by three different methods were compared. The intrinsic and extrinsic properties of TiO2, such as the particle size, surface area, pore-volume, pore-diameter, crystallinity as well as anatase, rutile and brookite phase ratios, could be controlled by the ultrasonic-assisted sol-gel method. During this preparation method, the effect of such important operating variables as the ultrasonic irradiation time, power density, the ultrasonic sources (bath-type and tip-type), magnetic stirring during synthesis, initial temperatures and size of the reactors are discussed here. It was found that each of the parameters played a significant role in controlling the properties of the TiO2 nano-particles. Among the three different methods, TiO2 photocatalysts prepared by ultrasonic (tip-US) assisted sol-gel possessed the smallest particle size, highest surface area and highest pore-volume than the catalysts prepared by the other two methods. 4-Chlorophenol was used as a pollutant to observe the photocatalytic degradation ability of the prepared photocatalysts and the TiO2 catalysts prepared by the bath-US ultrasonic-assisted sol-gel method were shown to be the most highly active. This is due to their high surface area and high pore-diameter. This study clearly demonstrates the importance and advantages of ultrasonication in the modification and improvement of the photocatalytic properties of mesoporous nano-size TiO2 particles. [Copyright &y& Elsevier]

Aqueous solutions of reactive blue 4 textile dye are totally mineralised when irradiated with TiO2 photocatalyst. A solution containing 4×10−4 M dye was completely degraded in 24 h irradiation time. The intensity of the solar light was measured using Lux meter. The results showed that the dye molecules were completely degraded to CO2, SO42−, NO3−, NH4+ and H2O under solar irradiation. The addition of hydrogen peroxide and potassium persulphate influenced the photodegradation efficiency. The rapidity of photodegradation of dye intermediates were observed in the presence of hydrogen peroxide than in its absence. The auxiliary chemicals such as sodium carbonate and sodium chloride substantially affected the photodegradation efficiency. High performance liquid chromatography and chemical oxygen demand were used to study the mineralisation and degradation of the dye respectively. It is concluded that solar light induced degradation of textile dye in wastewater is a viable technique for wastewater treatment. [Copyright &y& Elsevier]

The photocatalytic degradation of a textile dye, reactive red 2 in presence of sunlight using TiO2 and ZnO as photocatalysts is reported. The experimental studies have indicated complete decolourisation of the dye in a short period and degradation within 8 hr of irradiation. ZnO was found to be more effective in the removal of colour than TiO2, but the degradation efficiency was found to be more with TiO2. ZnO decomposes on prolonged irradiationwhile TiO2 is not photocorrosive. The percent degradationof the dye is high for both the catalysts at an optimum concentration of the catalysts. The first order rate constant is found to increase with decreasing dye concentration. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bi 2 WO 6 /TiO 2 nanorod heterojunction photocatalyst was prepared by ultrasonication assisted impregnation method. • The Bi 2 WO 6 /TiO 2 nanorod photocatalyst showed 13 folds enhancement in H 2 production than P25. • A direct Z-scheme heterojunction for charge transfer mechanism is proposed. In this work, Bi 2 WO 6 /TiO 2 nanorod heterojunction was prepared by sonochemical assisted impregnation method. After loading 2 wt% Bi 2 WO 6 on TiO 2 nanorods, the photocatalytic hydrogen production rate of 2026 µmol/h/g was achieved. Compared to commercial P25 and TiO 2 nanorods, ∼13 and ∼3 folds enhanced activity was observed. The excellent photocatalytic performance of Bi 2 WO 6 /TiO 2 nanorod photocatalyst was mainly attributed to i) reduction of bandgap due to heterojunction formation, ii) quick transport of photogenerated charge carriers, and iii) efficient charge carrier separation supported by UV-DRS, photocurrent measurement, Impedance study, and photoluminescence spectra analysis. The Z-scheme band alignment for Bi 2 WO 6 /TiO 2 nanorod heterojunction was proposed based on the Mott-Schottky measurement. This result demonstrated the effective utilization of Z-scheme heterojunction of Bi 2 WO 6 /TiO 2 for photocatalytic reduction application. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Designing high surface area and visible light active CNT-GR-TiO 2 nanocomposite. • Effect of graphene and CNTs on the band gap of TiO 2 and photocatalytic activity. • Increased water splitting activity of TiO 2 in presence of Ti3+ and oxygen defects. • Photocatalytic activity, CNT-GR-TiO 2 > GR-TiO 2 > TiO 2. Abstract Novel multiwalled carbon nanotubes-graphene-TiO 2 (CNT-GR-TiO 2) composite materials without noble metal co-catalysts are designed for photocatalytic decomposition of water using solar light. The CNT-GR-TiO 2 nanocomposite shows the highest H 2 production rate of 29 mmol h−1g−1 under the full spectrum of solar light irradiation. The rate of H 2 production is 8-fold higher than the commercial TiO 2 (Degussa P25) and the estimated solar energy conversion efficiency is 14.6%. Spectroscopic and photocatalytic studies reveal that graphene acts as an electron reservoir through which interfacial charge transfer occurs for water splitting. The UV–vis-DRS study shows that the absorption peak maximum for anatase TiO 2 occurs at ∼315 nm, which is shifted to ∼355 nm and 380 nm for GR-TiO 2 and CNT-GR-TiO 2 composites, respectively. The EPR spectra of GR-TiO 2 and CNT-GR-TiO 2 composites indicate that graphene and multiwalled carbon nanotubes in the composites promote the generation of Ti3+ and oxygen vacancies and in turn reduce the band gap of anatase TiO 2 from 3.32 eV to 2.79 eV. This is corroborated by XPS and photoluminescence analyses of the samples. The role of CNTs is to prevent the restacking of graphene nanosheets and provide additional electron transport channels thereby suppressing the recombination rate of electron-hole pairs in the CNT-GR-TiO 2 composite. The combination of all these factors results in increasing the hydrogen production rate from 19 mmol h−1 g−1 (anatase TiO 2) to 22 mmol h−1 g−1 (GR-TiO 2) to 29 mmol h−1 g−1 (CNT-GR-TiO 2). [ABSTRACT FROM AUTHOR]

Herein we report a simplified synthetic approach for a semiconductor photocatalyst (CdS) wrapped with a nanoscale thin-layer of semiconducting material (TiO 2 ) to overcome the instability issues, besides the improved catalytic efficiency. Images of HR-TEM and elemental mapping evidenced the presence of CdS that covered by ultra thin-layer of TiO 2 as shell. The UV–vis diffuse reflectance spectra showed red-shift in absorption edge in visible region. The photocatalytic water splitting towards hydrogen production using Na 2 S/Na 2 SO 4 as sacrificial agent was evaluated under UV–vis and visible light irradiation. The essential variables such as thickness of TiO 2 shell, amount of sacrificial agent and solution pH were fine tuned to achieve hydrogen generation of 5791 mL h −1  g −1 of catalyst. The higher efficiency is ascribed to core/shell morphology of CdS/TiO 2 system that channelled the excitons to the surface for the red-ox reactions rather than recombination. The catalytic stability result ascertained that the photo-corrosion is greatly suppressed. [ABSTRACT FROM AUTHOR]

A novel photocatalyst comprises of ZrO 2 TiO 2 immobilized on reduced graphene oxide (rGO) – a ternary heterojunction (ZrO 2 TiO 2 /rGO) was synthesized by using facile chemical method. The nanocomposite was prepared with a strategy to achieve better utilization of excitons for catalytic reactions by channelizing from metal oxide surfaces to rGO support. TEM and XRD analysis results revealed the heterojunction formed between ZrO 2 and single crystalline anatase TiO 2 . The mesoporous structure of ZrO 2 TiO 2 was confirmed using BET analysis. The red shift in absorption edge position of ZrO 2 TiO 2 /rGO photocatalyst was characterized by using diffuse reflectance UV–Visible spectra. ZrO 2 TiO 2 /rGO showed greater interfacial charge transfer efficiency than ZrO 2 TiO 2 , which was evidenced by well suppressed PL intensity and high photocurrent of ZrO 2 TiO 2 /rGO. The suitable band gap of 1.0 wt% ZrO 2 TiO 2 /rGO facilitated the utilization of solar light in a wide range by responding to the light of energy equal to as well as greater than 2.95 eV by the additional formation of excited high-energy electrons (HEEs). ZrO 2 TiO 2 /rGO showed the enhanced H 2 production than TiO 2 /rGO, which revealed the role of ZrO 2 for the effective charge separation at the heterojunction and the solar light response. The optimum loading of 1.0 wt% of ZrO 2 and rGO on TiO 2 showed the highest photocatalytic performance (7773 μmolh −1 g c a t − 1 ) for hydrogen (H 2 ) production under direct solar light irradiation. [ABSTRACT FROM AUTHOR]

Titanium dioxide is the most popular photocatalyst to degrade organic pollutants in air, as well as in water. The principal drawback preventing its commercial application lies in its limited absorption of the visible light (400–700 nm), while it is active under UV irradiation (≤387 nm). Supporting noble metals in the form of nanoparticles on TiO 2 increases its activity in the visible range. However, both the synthesis of noble metal nanoparticles and their deposition on TiO 2 are multi-step processes that often require organic solvents. Here, we deposit Ag nanoparticles from AgNO 3 on the surface of micrometric TiO 2 with H 2 O as a solvent and under ultrasound irradiation at 30 W cm −2 . Ultrasound increases the surface amount of Ag on TiO 2 with heterogeneous size distribution of Ag nanoparticles, which are bigger and overlaid (1–20 nm vs. 0.5–3 nm) compared to the sample obtained in traditional conditions (TEM images). While this change in morphology had no effect on acetone photodegradation under UV light, the 5%, 10%, and 20% Ag-TiO 2 degraded 17%, 20% and 24% acetone under visible light, respectively. The 10% by weight Ag-TiO 2 sample obtained in absence of ultrasound only degraded 14% acetone in 6 h, while the bare TiO 2 was not active. [ABSTRACT FROM AUTHOR]