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This research focused on the photodegradation of aqueous isopropanol in the presence of RGO/TiO2 photocatalysts, which were prepared by the hydrothermal method. Under the irradiation of the simulated sunlight AM1.5G, the photocatalytic activity of isopropanol degradation was studied. In addition, various initial isopropanol concentrations (20, 40, 60, 80, and 100 ppm) were employed in the photocatalytic reaction. P25RGO-0.01% was found to give the highest isopropanol removal of 92.24% at the initial isopropanol concentrations of 20 ppm. Such optimal loading of reduced graphene oxide can act as an electron trapping to suppress the possibility of the recombination of electron–hole pairs. Additionally, acetone was verified to be one of the main in1termediate products. Moreover, it was found that the acidic condition was advantageous to photodegrade isopropanol because of favorable conditions for forming hydroxyl radicals and superoxide radicals. The recyclability test was also verified by three sequent reactions and shown negligible decay of catalysts. This research demonstrated the feasibility of using photocatalysis to remove isopropanol wastewater in sunlight. [ABSTRACT FROM AUTHOR]

Photo-selective catalytic reduction of nitric oxide (NO) with methane (CH) over TiO and Pt/TiO photocatalysts was studied at reaction temperatures of 25, 50, and 100 °C. The activity of Pt/TiO in NO reduction was better than that of TiO. Conversion of NO by use of Pt/TiO and UV irradiation was up to 86.4 %. In-situ Fourier-transform infrared spectroscopy was successfully used to monitor the photoreaction process on TiO and Pt/TiO photocatalysts. During irradiation with UV light, bidentate nitrite disappeared and bidentate nitrate, monodentate nitrate, and isocyanate, an important intermediate, were generated. Adsorbed NH was found to be the final product of NO reduction after UV irradiation. We concluded that NO could be effectively reduced by CH under light irradiation at temperatures below 100 °C. A possible reaction mechanism is proposed on the basis of the intermediates and products generated by the photocatalyst under UV light irradiation. [ABSTRACT FROM AUTHOR]

Photo-selective catalytic reduction (photo-SCR) of nitric oxide (NO) was studied in the presence of water. The incipient wetness impregnation was applied to prepare 1 wt% PdO/TiO2 photocatalyst. Steady-state photoreaction was carried out in a continuous-flow photoreactor with 0.55–1.6 v% water at 30–120°C under UV-light intensity of ∼ 200 mW/cm2. The C3H8/NO molar ratio in the feed ranged from 0.8–16.8 at a volume hourly space velocity (VHSV) from 330–1090 h−1. The result indicates that the increase of temperature has played an important role in inhibiting NO transformation to NO2 under the humid condition. Another important factor for maximizing denitrification (reduction of nitrogen oxides, DeNOx) efficiency was C3H8/NO ratio. An increase of temperature at a suitable C3H8/NO ratio can minimize NO2 formation, which can lead to high NO removal efficiency of more than 90% at a temperature of 70–100°C. In addition, the mechanism of palladium transformation during photoreaction is proposed, to explain the influence of Pd on the improvement of NO removal. [ABSTRACT FROM PUBLISHER]

Photo-assisted catalytic reduction of nitric oxide (NO) was studied over different metal-loaded TiO2 catalysts at room temperature. The activities of metal-loaded (Pt, Ag, Cu) TiO2 photocatalysts, prepared by the sol-gel method, were compared in a batch system using CH4 as the reducing agent. The Pt/TiO2 catalyst showed the highest activity for NO reduction. Thus, Pt/TiO2 was coated on optical fibres and used in a continuous-flow optical-fibre photoreactor. The optical-fibre photoreactor provides light irradiation on the photocatalyst through the optical fibre, thus improving the efficiency of photoreactions. Ten per cent conversion of NO was found using CH4 as the reducing agent. The NO conversions increased to 90% in the presence of water vapour and oxygen. However, most NO was oxidized to NO2. Hydrogen had superior reducing capabilities over CH4 on Pt/TiO2 photocatalyst, and the conversion of NO reached 85%. But the conversion of NO was substantially decreased to less than 10% in the presence of water vapour and oxygen. Our research proposed an alternative way to reduce NO pollutant to N2 at room temperature using an optical-fibre photoreactor, which could possibly utilize sunlight in the future. [ABSTRACT FROM AUTHOR]

A series of mesoporous TiO2/SBA-15, Cu/TiO2 and Cu/TiO2/SBA-15 composite photocatalysts were prepared by sol–gel synthesis for photoreduction of CO2 with H2O to methanol. It was found that optimum amount of titanium loading of TiO2/SBA-15 was 45 wt% which exhibited higher photoreduction activity than pure TiO2. An addition of copper on TiO2 or TiO2/SBA-15 catalyst as cocatalyst was found to enhance the catalytic activity because copper serves as an electron trapper and prohibits the recombination of hole and electron. [ABSTRACT FROM AUTHOR]

Abstract: Photo selective catalytic reduction (SCR) of nitric oxide (NO) was studied on Pd loaded TiO2 at room temperature. The NO conversions on photocatalyst prepared via the incipient wetness impregnation, was evaluated using a steady-state continuous-flow photoreactor under UV light irradiation. The photo-activity of the Pd/TiO2 catalyst could be significantly increased after reduction with H2 at 500°C for 2h. It was found that Pd improved the adsorption of C3H8 thus increased NO conversion up to 90%. N2O was not detected in the effluent. The results indicate that Pd/TiO2 is an effective photocatalyst to reduce NO pollutant at room temperature to N2. [Copyright &y& Elsevier]

Various sol–gel procedures and post-treatments were applied to modify the distribution of Cu on the surface of Cu/TiO2 catalysts in order to increase the production of methanol in the photoreduction of CO2. The chemical states of Cu in 2wt.% Cu/TiO2 were characterized in detail as a follow-up the high Cu dispersion found in previous studies. XRD, XPS and XAS analysis reveal that the active Cu state for the photoreaction of CO2 is suggested to be highly dispersed Cu(I). The photoactivity decreases when Cu(I) changes to Cu(0) or aggregates after reduction with H2. An optimal distribution of Cu exists between the surface and bulk of TiO2 particles. The photocatalytic activity attains maximum when near 25% of the total Cu loading is located on the outermost surface of a TiO2 particle. Cu/TiO2 is a more active catalyst than Ag/TiO2 because Cu particles act as electron trapping sites while still maintain the mobility of photoelectrons. [Copyright &y& Elsevier]

A series of vanadium-doped TiO2 catalysts were synthesized by two modified sol–gel methods. V-doped TiO2 was found to be mainly preserved its anatase phase after calcination at 400 °C. The TEM micrographs showed the sizes of primary particles were in the range of 6–20 nm. The increase of vanadium doping promoted the particle growth, and enhanced “red-shift” in the UV-Vis absorption spectra. The XPS (X-ray photoelectron spectroscopy) could not detect vanadium indicating negligible vanadium on the surface of catalysts, furthermore, there were also no peak of vanadium oxide in the XRD patterns. XAS (X-ray absorption spectroscopy) analysis indicating V4+ instead of V5+ implied that vanadium either substituted Ti4+ site or embedded in the vacancy of TiO2 structure. Therefore, vanadium was concluded to be highly dispersed inside the TiO2 structure. The photocatalytic activity was evaluated by the degradation of crystal violet (CV) and methylene blue (MB) under visible light irradiation. The degradation rate of CV and MB on V-doped TiO2 were higher than those of pure TiO2. As the results, V-doped TiO2 possessed better absorption ability of visible light. [Copyright &y& Elsevier]

Copper-loaded titania (Cu/TiO2) was synthesized via an improved modified sol–gel process. Photocatalysts were applied to the CO2 photocatalytic reduction and the yield of the major product, methanol, was used to evaluate the photocatalytic performance. Copper precursors and the adding time with sol as well as posttreatments were studied to explore the relationships between the characteristics and the activity of the photocatalysts. The results revealed that Cu/TiO2 prepared from copper chloride and added in the early sol–gel stage was more photoactive than that from copper acetate. Additional H2 reduction of calcined catalysts before the photoreduction CO2 decreased the yield of methanol due to the change of copper dispersion and oxidation state. TPR, XPS, and XAS measurements verified the oxidation state of Cu on Cu/TiO2 catalysts. The results indicated that the primary Cu(I) served as an active site. The zeta potentials of catalysts were measured and compared, showing that a higher positive zeta potential at pH 7 would lead to higher activity. Under 30-h UVC (254 nm) irradiation, the best catalyst gave a methanol yield above 600 μmol/gcat. Switching to UVA (365 nm) resulted in a significant decrease of methanol yield in the range of 10 μmol/gcat. [Copyright &y& Elsevier]

[Display omitted] • The geomimetic concept enabled the successful one-step preparation of an N-doped reduced TiO 2 porous coating layer using atmospheric plasma spraying technology. • Acetamide and urea were used for nitrogen doping in TiO 2. • The N-doped reduced TiO 2 had excellent photocatalytic TC and CIP degradation performance, recyclability and structural stability. • This green, time-saving, cost-effective, diversified, and forward-looking preparation process is highly suitable for mass production. N-doped reduced TiO 2 porous photocatalyst coatings are prepared by atmospheric plasma spraying (APS) technology combined with the geomimetic concept. Unlike traditional photocatalyst preparation methods, this method can be manufactured on a large scale and considerably shortens the preparation time by only 15 min. In this study, acetamide and urea, with one or two nitrogen atoms in the structure, were used as dopants to prepare N-doped TiO 2 (T1N and T2N) for photocatalytic antibiotic degradation. Tetracycline (TC, 20 ppm/100 mL) and ciprofloxacin (CIP, 20 ppm/100 mL) were photodegraded under AM1.5G solar simulator illumination. The T1N obtained a higher lattice-nitrogen ratio than T2N, which gave T1N better photocatalytic activity. The rate constants of photodegradation of TC and CIP under simulated solar irradiation are 1.70 and 1.42 (×10−2 min−1), which are more than twice that of T2N and nearly 20 times higher than that of pristine TiO 2. Moreover, after 10 rounds of recycling tests, the photocatalyst showed good performance and structural stability. The scavenger test suggested that ̇O 2 − is the most important reactive species in TC degradation, while ̇OH and h+ play an important role in CIP degradation. The degradation pathways of TC and CIP were proposed. This photocatalyst coating preparation method is suitable for large-scale production and is a time-saving, sustainable, diversified, and future-looking technology. [ABSTRACT FROM AUTHOR]

Abstract: Photocatalytic TiO2 thin films were prepared via an electron beam-induced deposition (EBID) method. The effects of post-calcination treatment on the properties of the prepared TiO2 thin films were studied. X-ray diffraction (XRD), scanning electron microscope-energy dispersive spectrometry (SEM-EDS), and UV–V is absorption spectrometry were performed to reveal the crystallinity, surface morphology, chemical composition, and light absorbance of the prepared TiO2 thin films. The photoelectrochemical characteristics of the TiO2 thin films were investigated with a potentiostat. Under UV irradiation, a photocurrent of ˜2.1 mA was observed for the TiO2 thin film with post-calcination at 500 °C. A water-splitting reaction was conducted over the TiO2 thin film with the best photoelectrochemical performance. The yields of hydrogen and oxygen were 59.8 and 30.6 μmole, respectively, after 8 h of reaction under UV irradiation. [ABSTRACT FROM AUTHOR]

Carbon dioxide was photocatalytically reduced to produce methanol in an aqueous solution using 254 nm UV irradiation. Titania and Cu-loaded titania were synthesized by an improved sol–gel method using a homogeneous hydrolysis technique. The grain size of TiO2 and Cu/TiO2 were uniform and average diameters were approximately 20 nm. Photocatalytic reduction was conducted in a quartz reactor with a UV lamp irradiating at the center. XPS analysis reveals that Cu 2p3/2 is 933.4 eV indicating primary Cu2O species on the TiO2 supports. EDX and XPS revealed that most copper clusters were on the TiO2 surface. The optimum amount of copper loading was 2.0 wt.% for the highest dispersion among catalysts. The methanol yield of 2.0 wt.% Cu/TiO2 was 118 μmol/g following 6 h of UV illumination. The yield was much higher than those of sol–gel TiO2 and Degussa P25, whose yields were 4.7 and 38.2 μmol/g, respectively. The methanol yield reached a steady-state 250 μmol/g after 20 h of irradiation. Experimental results indicated that the methanol yield was significantly increased by adding NaOH. The caustic solution dissolved more CO2 than did pure water. In addition, the OH− in aqueous solution also served as a strong hole scavenger. The redistribution of the electric charge and the Schottky barrier of Cu and TiO2 facilitates electron trapping via supported Cu. The photocatalytic efficiency of Cu/TiO2 was markedly increased because of the lowering the re-combination probability for hole–electron pairs. The highest quantum and energy efficiencies achieved were 10 and 2.5%, respectively. [Copyright &y& Elsevier]

The parent TiO 2 , platinum and copper doped TiO 2 photocatalysts with 0.5–2 wt. % of Pt, 0.5–2 wt. % Cu and 1 wt. % Pt combined with 1 wt. % Cu were prepared by the sol-gel method. All the prepared photocatalysts were tested for the CO 2 photocatalytic reduction in a stirred batch reactor. The main reaction product was methane, however, hydrogen and carbon monoxide were also detected. The textural, (micro)structural, optical and electronic properties of photocatalysts were characterized in detail by low-temperature nitrogen physisorption, X-ray powder diffraction, EDX, HRTEM, X-ray fluorescence, X-ray photon spectroscopy, scanning electron microscope, transmission electron microscope and diffuse reflectance UV–vis spectroscopy. The photoelectrochemical characteristics of the photocatalysts were determined using photoelectric spectrometry. The highest yields of CH 4 , H 2 and CO were achieved in the presence of 2 wt. % Cu/TiO 2 , 0.5 wt. % Cu/TiO 2 and pure, amorphous TiO 2 . Based on the conducted experiments it was suggested that both the amount of chemisorbed oxygen or/and hydroxyl species on the TiO 2 surface and specific surface area of photocatalyst highly influence its photocatalytic activity. [ABSTRACT FROM AUTHOR]

In this paper, V and W codoped TiO 2 catalysts were prepared and coated on the surface of honeycomb support. The V 4+ doped in TiO 2 lattice enhanced the visible light absorption of TiO 2 while the V 2 O 5 on the surface of TiO 2 and W 6+ in TiO 2 lattice could trap photogenerated electrons and transfer them to CO 2 and water adsorbed on the surface of catalyst, resulting in effective separation of photogenerated charges. CO 2 photocatalytic reduction over V and W codoped TiO 2 catalyst was conducted in an internal-illuminated honeycomb photoreactor under simulated sunlight irradiation. Due to the strong visible light absorption and effective separation of photogenerated charges caused by V and W codoping and stable chemical states of V and W during photocatalytic reaction, the V and W codoped TiO 2 catalysts exhibited stable and enhanced photocatalytic activity comparing with pristine TiO 2 and single metal doped TiO 2 . [ABSTRACT FROM AUTHOR]

In this paper, Pt nanoparticles were deposited on TiO 2 nanocrystals with coexposed {101} and {001} facets by photodeposition and chemical reduction methods using H 2 PtCl 6 or Pt(NH 3 ) 4 Cl 2 as precursors, respectively. The deposition method and Pt precursors exhibited great influence on the particle size, distribution, and chemical states of Pt nanoparticles, which further affected the recombination of photogenerated charges. The Pt/TiO 2 catalyst prepared by chemical reduction of H 2 PtCl 6 had the highest H 2 and CH 4 yield of 9.9 and 4.6 μmol g − 1 h − 1 , resulting from the lowest recombination rate of photogenerated charges caused by the high Pt 0 /Pt II ratio and homogeneous distribution of Pt nanoparticles over TiO 2 facets. [ABSTRACT FROM AUTHOR]

In developing a higher activity for NOx abatement from stationary emission sources, photo-assisted selective catalytic reduction (photo-SCR) was systematically investigated over TiO 2 supported on a spherical α-Al 2 O 3 /γ-Al 2 O 3 . The formation of NO 2 was virtually suppressed in the reaction temperature range of 110–200 °C. The NOx removal efficiencies of TiO 2 /γ-Al 2 O 3 photocatalyst at 120 °C for real flue gas (in pilot-scale photoreactor) and simulated flue gas (in lab-scale photoreactor) were 68–75% and 43.5%, respectively, in the presence of reducing reagent (C 4 H 10 ). SEM and XPS techniques revealed that sulfur temporarily occupied the active sites of the photocatalyst, causing deactivation. Spent TiO 2 /γ-Al 2 O 3 photocatalyst was regenerated via desulfurization by either air or hydrogen at 400–500 °C. The effects of regeneration temperature and regeneration time on the photocatalytic activity are methodically investigated, demonstrating that using hydrogen at 500 °C in 1 h could completely regenerate the spent photocatalyst. [ABSTRACT FROM AUTHOR]

Abstract: Anthropogenic activities are causing an increase in greenhouse gases in the atmosphere, with carbon dioxide (CO2) being the key cause of global warming. The conversion of CO2 into valuable hydrocarbons serves as a promising route for mitigating the effects of global warming and meeting future energy demands. Herein, we show the comparison between the photocatalytic reduction of CO2 for metal coated TiO2 nanoparticles in a slurry batch annular reactor system and metal coated TiO2 monoliths in an internally illuminated photoreactor system using the 1wt% Pd/0.01wt% Rh-TiO2 catalyst. Carbon based fuels, such as methane, methanol or acetaldehyde were produced in the gas phase from the CO2 reduction with water by titania nanoparticles modified by Pd and Rh for improved reactivity. The modified photocatalysts synthesized by the improved sol–gel method were tested under UV light irradiation. The quantum efficiency of the internally illuminated monolith reactor was near one order of magnitude higher than the slurry batch annular reactor. This efficiency was due to the reactor''s flexible configuration; which allows maximum exploitation of the combined advantages of the high surface area of the monolith and the elimination of uneven light distribution via the optical fibres. [Copyright &y& Elsevier]

Abstract: A family of Cu/TiO2 catalysts was prepared using a refined sol–gel method, and tested in the photocatalytic reduction of CO2 by H2O to CH4 using a stirred batch, annular reactor. The resulting photoactivity was benchmarked against pure TiO2 nanoparticles (synthesised by an identical sol–gel route). CO2 photoreduction exhibited a strong volcano dependence on Cu loading, reflecting the transition from 2-dimensional CuOx nanostructures to 3-dimensional crystallites, with optimum CH4 production observed for 0.03wt.% Cu/TiO2. [Copyright &y& Elsevier]

Abstract: Photocatalytic reduction of nitric oxide was studied on a PtO x PdO y /TiO2-coated monolith photoreactor using propane as the reducing agent. The performance of NO reduction was compared under three reaction conditions including NO/propane, NO/propane/O2 and NO/propane/H2O at three reaction temperatures, 25, 70 and 120°C. The NO/propane system showed the best performance of near 90% conversion at 25°C. The NO conversion decreased slightly as temperature increased in NO/propane system, however, NO/propane/O2 and NO/propane/H2O systems showed an opposite trend. Oxygen and water significantly inhibited the reduction of NO because oxygen competed with NO as oxidant, and water interfered the adsorption of both NO and propane. TiO2 became super-hydrophilic under UV-light irradiation thus the catalyst surface was easily covered by water in moisture condition. By increasing the reaction temperature, water tended to desorb from the catalyst surface thus released more active sites for NO photoreduction. An in situ FTIR was also performed to study the intermediate species of the NO/propane and NO/propane/O2 systems under UV-light irradiation. The results indicated that NO went through both oxidation and reduction with C3H8 on PtO x PdO y /TiO2. The reaction path of NO might change with increasing temperature. [Copyright &y& Elsevier]

Abstract: The composite photocatalyst comprising p-type NiO and n-type TiO2 showed improved photoactivity due to the inhibition of electron–hole recombination. A series of P–N junction photocatalysts, NiO/TiO2, were prepared by incipient wetness impregnation. The photocatalysts were characterized by UV–vis spectroscopy, XRD and XPS. The photoactivity of photocatalysts was tested by the degradation of methylene blue. The results showed that 0.5wt.% NiO/TiO2 had the highest activity as compared with TiO2. A P–N junction mechanism was proposed and verified that the photocurrent could be enhanced under forward bias in the NiO/TiO2 film. The photoactivity enhancement is attributed to P–N junction and co-catalyst effects. [Copyright &y& Elsevier]

The mechanism of photocatalytic conversion of CO2 and H2O over copper oxide promoted titania, Cu(I)/TiO2, was investigated by means of in situ DRIFT spectroscopy in combination with isotopically labeled 13CO2. In addition to small amounts of 13CO, 12CO was demonstrated to be the primary product of the reaction by the 2115 cm-1 Cu(I)-CO signature, indicating that carbon residues on the catalyst surface are involved in reactions with predominantly photocatalytically activated surface adsorbed water. This was confirmed by prolonged exposure of the catalyst to light and water vapor, which significantly reduced the amount of CO formed in a subsequent experiment in the DRIFT cell. In addition, formation of carboxylates and (bi)carbonates was observed by exposure of the Cu(I)/TiO2 surface to CO2 in the dark. These carboxylates and (bi)carbonates decompose upon light irradiation, yielding predominantly CO2. At the same time a novel carbonate species is produced (having a main absorption at 1395 cm-1) by adsorption of photocatalytically produced CO on the Cu(I)/TiO2 surface, most likely through a reverse Boudouard reaction of photocatalytically activated CO2 with carbon residues. The finding that carbon residues are involved in photocatalytic water activation and CO2 reduction might have important implications for the rates of artificial photosynthesis reported in many studies in the literature, in particular those using photoactive materials synthesized with carbon containing precursors. [ABSTRACT FROM AUTHOR]