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Summary: A novel Bi2WO6/rGO/3D‐GCN composite with 2D/2D/3D heterojunction is synthesized by a simple microwave‐assisted method and used as a visible‐light‐responsive photocatalyst in the CO2 reduction. The chemical properties and morphology of prepared photocatalysts are identified by a variety of analytic tools and spectroscopies. As a result, the heterojuncted Bi2WO6/3D‐GCN exhibits superior CO2 reduction performance as compared to the pristine 3D‐GCN, which may be caused by the intimate contact between Bi2WO6 and 3D‐GCN. The harvest of visible‐light absorption, reduced charge transfer resistance and suppressed recombination of electron‐hole pairs are accountable for surpassing performance of Bi2WO6/3D‐GCN. Upon further incorporation of rGO into Bi2WO6/3D‐GCN heterojunction, the photocatalytic production of CO can be notably boosted by ca. 7.9‐fold higher than 3D‐GCN, suggesting the key contribution of rGO in facilitating the interfacial charge transfer kinetics and increasing CO2 uptake. This work exemplifies a time and energy‐saving method to prepare the unique 3D GCN with laminated hexagonal structure which can serve as a shuttle for Bi2WO6 heterojunction and rGO incorporation. This Bi2WO6/rGO/3D‐GCN photocatalyst could offer the potential applications in the natural solar conversions of CO2. [ABSTRACT FROM AUTHOR]

Summary: Exfoliated vanadium aluminum carbide (V2AlC) MAX nanosheets coupled with porous graphitic carbon nitride to construct 2D/2D V2AlC MAX/g‐C3N4 heterojunction for photocatalytic CO2 reduction through dry reforming of methane has been investigated. Good interfacial interaction was achieved which enabled proficient charge carrier separation with promoted light absorption. The optimized 10 wt%V2AlC MAX/g‐C3N4 was more proficient with CO and H2 evolution rates of 118.74 and 89.52 μmole g−1 h‐1 at selectivity 57.01 and 42.98%, respectively. This efficiency for CO and H2 evolution rate was 2.21‐ and 1.99‐folds superior to using pure g‐C3N4. This improvement is due to good interfacial contact and efficient charge carrier separation by MAX, which increases photo‐induced charge carrier lifetime. The performance was further investigated with different reforming systems to manipulate the effective utilization of holes to extend charges recombination rate. Using CO2 reduction with hydrogen, CO2 methanation and the reverse water‐gas shift reaction were activated, whereas CO2 with water promoted more methane formation. By investigating CH4/CO2 feed ratios, the highest yield rates attained with the ratio of 1:0, confirming V2AlC based‐composite effectively activates both gases as evidenced by their apparent quantum yields. This study provides a promising route for the fabrication of noble‐metal‐free nanocomposite and will be useful for future energy and environmental applications. [ABSTRACT FROM AUTHOR]

A series of composite γ-Fe2O3/g-C3N4 (denoted as xFeCN with x equal 5, 10, 15, and 20 of γ-Fe2O3 percentage in weight) was prepared by calcination and precipitation-impregnation methods. X-ray diffraction (XRD), Fourier transform infrared (FTIR), and X-ray photoelectron spectrometry (XPS) characterizations indicated the successful synthesis of Z-scheme FeCN composites. A red shift of the light absorption region was revealed by UV-vis diffuse reflectance spectroscopy (UV-DRS). In addition, photoluminescence spectroscopy (PL) spectra showed an interface interaction of two phases Fe2O3 and g-C3N4 in the synthesized composites that improved the charge transfer capacity. The photocatalytic activity of these materials was studied in the photoreduction of CO2 with H2O as the reductant in the gaseous phase. The composites exhibited excellent photoactivity compared to undoped g-C3N4. The CH4 production rate over 10FeCN and 15FeCN composites (2.8 × 10−2 and 2.9 × 10−2 μmol h−1 g−1, respectively) was ca. 7 times higher than that over pristine g-C3N4 (0.4 × 10−2 μmol h−1 g−1). This outstanding photocatalytic property of these composites was explained by the light absorption expansion and the prevention of photogenerated electron-hole pairs recombination due to its Z-scheme structure. [ABSTRACT FROM AUTHOR]

Summary: Solar‐driven converting CO2 to value‐added chemicals can not only address the ever‐growing energy crisis, but also simultaneously mitigate CO2 emission. Although much progress has been made in the last decade, it still remains great challenge to achieve the efficient reduction of CO2 with desirable productivity and high product selectivity because CO2 is a thermodynamically stable and inert molecule with large bond energy. Design and synthesis of efficient catalyst play a pivotal role in promoting the activity and selectivity of photocatalytic CO2 reduction. Apart from the active sites engineering, manipulation of the charge separation and light harvesting efficiency or prolonging the lifetime of photogenerated carriers also greatly matters. Consequently, this review summarizes recent advances in photocatalyst design for CO2 conversion from two major aspects, namely active sites engineering and carriers lifespan prolonging. Firstly, we sort out the fundamental principles and merits of artificial photosynthesis in order to provide readers with a current snapshot of this rapidly developed field. Subsequently, various catalyst engineering strategies, including doping, alloying, Z‐scheme structure construction, are discussed in detail. Finally, some challenging issues as well as insights into the future development of artificial photosynthesis are presented. [ABSTRACT FROM AUTHOR]

Summary: The two‐layer photocatalytic membranes fabricated from a porous polyethersulfone‐TiO2 (PES‐TiO2) as a photocatalytic layer and a thin nonporous layer of poly‐ether‐block‐amide (PEBAX‐1657) as a selective layer were used to solve the problems of slurry photocatalyst systems and substitute a single operating unit for simultaneous separation and conversion of CO2. The photocatalytic features, hydrophilicity, surface chemistry, and morphology of photocatalytic membranes were characterized by Ultraviolet–visible (UV‐visible), contact angle, Attenuated Total Reflection‐Fourier Transforms Infrared (ATR‐FTIR), and (Scanning Electron Microscopy) SEM, respectively. Compared with membrane without any nanoparticle, the separation performance of nanocomposite membranes using the gas mixture (containing CO2 and CH4 with the molar ratio of 1:4), as the feed, was slightly increased by adding TiO2 content in the support layer. The effects of TiO2 nanoparticle contents, water flow rates as well as light powers on the photoreduction of CO2 to methanol in terms of methanol concentration and production yield were investigated under Ultraviolet (UV) irradiation. As depicted by UV‐vis analysis, the UV irradiation absorption of photocatalytic membranes increased with increasing of TiO2 contents. Moreover, the ATR‐FTIR results confirmed the presence of TiO2 nanoparticle on the photocatalytic membrane surface. The photocatalytic performance revealed that utilizing simultaneous separation and conversion for CO2 photoreduction in the presence of water represented the high methanol production yield about 697 μmol/gcat.h at 5 wt. % of TiO2 nanoparticle contents, 3 mL/min of water flow rate and 8.84 W/cm2 of light power. Meanwhile, the possible mechanism of the TiO2 photocatalytic performance for CO2 photoreduction to methanol was clarified. In addition, it was confirmed that the photocatalytic membranes were efficient until after four runs. Therefore, the utilization of photocatalytic membrane is an effective approach to improve the beneficial combination of photocatalytic process and membrane technology, simultaneously. [ABSTRACT FROM AUTHOR]

Ammonium ( NH 4 + ) is an undesirable by-product of photocatalytic nitrate ( NO 3 − ) reduction since it is harmful to aquatic life once it converts into ammonia (NH3). This research investigated the removal efficiency of NO 3 − and for the first time quantified the relationships of initial nitrate concentrations ([ NO 3 − ]0) and photocatalyst dosages on the remaining ammonium ( NH 4 + ) in synthetic wastewater using photocatalytic reduction process with either nanoparticle titanium dioxide (TiO2) or 1.0%Ag-TiO2 under Ultraviolet A (UVA). The experiments were systematically carried out under various combinations of [ NO 3 − ]0 (10, 25, 50, 80, and 100 mg-N/L) and photocatalyst dosages (0.1, 0.5, 1.0, and 2.0 g). The NO 3 − removal efficiency of both photocatalysts was 98.96-99.98%, and the catalytic selectivity products were nitrogen gas (N2), nitrite ( NO 2 − ), and NH 4 + . Of the two photocatalysts under comparable experimental conditions, 1.0%Ag-TiO2 provided better NO 3 − removal efficiency. For both photocatalysts, the remaining NH 4 + was predominantly determined by [ NO 3 − ]0; higher [ NO 3 − ]0 led to higher NH 4 + . Multiple linear regression analysis confirmed the dominant role of [ NO 3 − ]0 in the remaining NH 4 + . The photocatalyst dosage could play an essential role in limiting NH 4 + in the treated wastewater, with large variation in [ NO 3 − ]0 from different sources. [ABSTRACT FROM AUTHOR]

Novel nanocomposites have been prepared by intercalating TiO2 nanoparticles into talc. The nanocomposites have been verified by X-ray diffraction (XRD) from the appearance of a characteristic diffraction peak of TiO2. Thermal behavior of the prepared samples is examined by thermogravimetric analyzer (TGA), scanning electron microscope (SEM), and energy dispersive spectrometer (EDS), which have shown no TiO2 particles on the surface of the talc. The TiO2 particles are found in the layers of talc by transmission electron microscopy (TEM) and the Brunauer-Emmett-Teller (BET) method, which have shown the increase of specific surface areas and total pore volumes and the decline of average pore diameters. As the strong adsorption ability of talc can intensify the power of photon absorption and capture-recombination carriers, more than 99.5% of 2,4-dichlorophenol can be degraded in 1 h by the nanocomposite under an ultraviolet lamp in neutral solution and room temperature after reaching adsorption equilibrium, and the result of adsorbance is in accord with the first-order kinetic. The degradation rate was maintained at about 99% after 20 times. Therefore, the prepared talc/TiO2 nanocomposite is an efficient, stable, and recyclable material for wastewater treatment. [ABSTRACT FROM AUTHOR]

Summary: Currently, the best approach to solve the increasing CO2 emission and energy shortage problems comes from catalytic CO2 reduction into organic fuels using solar radiation. Using inexpensive coal samples, here we synthesized coal‐based luminescent carbon dots (CDs) by H2O2 oxidation method. Coated composite nanoparticle Ag/CDs were then fabricated using a simple silver mirror reaction to attach CDs in situ to Ag surface. The lattice structure of Ag/CDs was characterized, and the performance of photocatalytic CO2 reduction into hydrocarbons was investigated. The surface of the composite contains a large number of oxygen groups and mesoporous interface from accumulation of uniform‐sized particles, demonstrating good adsorption capability for CO2. Thanks to the broad absorption spectra extending into the visible range and low recombination rate of photogenerated electron‐hole pairs, the composite nanoparticles can be applied in the photocatalytic CO2 reduction. Compared with individual Ag and CDs, Ag/CDs exhibit enhanced photocatalytic activity for CO2 reduction. Coal‐based luminescent carbon dots was prepared by H2O2 oxidation method. Composite nanoparticle catalyst Ag/CDs were then fabricated by a simple silver mirror reaction, and test the CO2 photocatalytic reduction performance of the synthesized catalyst. [ABSTRACT FROM AUTHOR]

Constructing near-infrared-light-mediated core-shell nanostructures incorporating upconversion nanoparticles (UCNPs) and semiconductors is of great importance for potential applications in photocatalysis, nano-biomedical engineering, solar cell, etc. In this work, we have demonstrated a two-step solution process to synthesize UCNPs@Zn0.5Cd0.5S core-shell nanoparticles (CSN). Firstly, a layer of AA-Zn(Cd)[OH]4− composites was coated on UCNPs to form UCNPs@AA-Zn(Cd)[OH]4− composites, which has been converted to UCNPs@Zn0.5Cd0.5S CSN via sulfidation reaction process using thioacetamide (TAA) as the sulfur source. Moreover, the UCNPs@Zn0.5Cd0.5S yolk-shell nanoparticles (YSN) have been obtained from the UCNPs@Zn0.5Cd0.5S CSN after calcination at 400°C, which show significantly photocatalytic activity for reduction of Cr(VI) under near-infrared light. All these can be attributed to the enhanced crystallization degree, resulting in enhanced energy transfer efficiency and separation efficiency of the photogenerated electrons and holes. An alternative strategy is provided in this study for fabrication of UCNP/semiconductor composites for various applications. [ABSTRACT FROM AUTHOR]

A series of three-dimensional microflower-like Ag/Bi2WO6 composites were synthesized through a simple and practical photoreduction process with different photoreduction times. The UV-visible diffuse reflectance spectra indicate that the spectrum of Ag/Bi2WO6 is significantly red-shifted compared to pure Bi2WO6 microspheres in the visible light region. The photocatalytic activities of the as-prepared samples were evaluated by the decolorization of rhodamine B under visible light irradiation. The photocatalytic reaction rate constants of the Ag/Bi2WO6 with a photoreduction time of 20 min was 3.60 times bigger than those of pure Bi2WO6. The enhanced photocatalytic activity could be attributed to the synergistic effect of increased light absorption range and the effective separation of photogenerated carriers caused by Ag nanoparticles. [ABSTRACT FROM AUTHOR]

Summary: Photocatalytic conversion of CO2 into value‐added hydrocarbon fuels and/or useful chemical products, using solar energy, has been the focus of active research, owing to its tremendous potential to provide a green fuel (eg, methanol) and simultaneously mitigate global warming by reducing CO2 levels in the atmosphere. CO2 photocatalytic reduction yields various hydrocarbon products. In this paper, we focus on methanol as it is an easily transportable energy‐dense fuel with multifarious applications in the automobile, industrial, and petrochemical sector. The photocatalytic conversion rate of CO2 to methanol depends on 3 factors: the photocatalyst used, photoreactor design, and experimental parameters (or variables). The last factor—experimental parameters—forms the basis of this review paper. These parameters include the reaction temperature, CO2 pressure, solvent used, intensity, wavelength, and duration of the incident light, concentration of organic impurities adsorbed on catalytic surface, addition of hole scavengers, type of reductant used, catalyst loading method, catalyst concentration, and the dissolved oxygen concentration. There have been numerous published works aiming to improve the methanol formation rate by optimizing these experimental parameters. In this paper, we consolidate and review these parameters, and investigate how optimizing them can enhance the photocatalytic conversion rate of CO2 into methanol, thus ushering in the era of a green methanol‐based economy. [ABSTRACT FROM AUTHOR]

Summary: Photocatalytic conversion of CO2 into value‐added hydrocarbon fuels and/or useful chemical products, using solar energy, has been the focus of active research, owing to its tremendous potential to provide a green fuel (eg, methanol) and simultaneously mitigate global warming by reducing CO2 levels in the atmosphere. CO2 photocatalytic reduction yields various hydrocarbon products. In this paper, we focus on methanol as it is an easily transportable energy‐dense fuel with multifarious applications in the automobile, industrial, and petrochemical sector. The photocatalytic conversion rate of CO2 to methanol depends on 3 factors: the photocatalyst used, photoreactor design, and experimental parameters (or variables). The last factor—experimental parameters—forms the basis of this review paper. These parameters include the reaction temperature, CO2 pressure, solvent used, intensity, wavelength, and duration of the incident light, concentration of organic impurities adsorbed on catalytic surface, addition of hole scavengers, type of reductant used, catalyst loading method, catalyst concentration, and the dissolved oxygen concentration. There have been numerous published works aiming to improve the methanol formation rate by optimizing these experimental parameters. In this paper, we consolidate and review these parameters, and investigate how optimizing them can enhance the photocatalytic conversion rate of CO2 into methanol, thus ushering in the era of a green methanol‐based economy. [ABSTRACT FROM AUTHOR]

Titanium dioxide nanoparticles were prepared by a modified sol-gel route. Titanium butoxide was used as precursor and nebulizer was used for a fine spray of particles. The prepared powders were characterized by FT-IR, SEM, XRD, and TGA-DTA methods. The results indicated that nanoparticles with small size and high surface area were synthesized. XRD result indicated that TiO2 nanoparticles were obtained in pure anatase crystalline form with a crystallite size of 40 nm. The catalytic activity of as-synthesized nanoparticles was tested for the degradation of formic acid and toluene. [ABSTRACT FROM AUTHOR]

Investigation into the reduction of Cr(VI) in aqueous solution was carried out through some batch photocatalytic studies. The photocatalysts used were silica coated nickel ferrite nanoparticles (NiFe2O4-SiO2), nickel ferrite titanium dioxide (NiFe2O4-TiO2), nickel ferrite silica titanium dioxide (NiFe2O4-SiO2-TiO2), and titanium dioxide (TiO2). The characterization of the materials prepared via stepwise synthesis using coprecipitation and sol-gel methods were carried out with the aid of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, thermal gravimetric analysis (TGA), and vibrating sample magnetometry (VSM). The reduction efficiency was studied as a function of pH, photocatalyst dose, and contact time. The effects of silica interlayer between the magnetic photocatalyst materials reveal that reduction efficiency of NiFe2O4-SiO2-TiO2 towards Cr(VI) was higher than that of NiFe2O4-TiO2. However, TiO2 was observed to have the highest reduction efficiency at all batch photocatalytic experiments. Kinetics study shows that photocatalytic reduction of Cr(VI) obeyed Langmuir-Hinshelwood model and first-order rate kinetics. Regenerability study also suggested that the photocatalyst materials can be reused. [ABSTRACT FROM AUTHOR]

The presence of bromate in water is a well-known problem because of its toxic effects on human health, particularly its carcinogenic potential. Photocatalytic reduction is an attractive process for bromate removal. F- and Fe-codoped TiO2 (F-Fe-TiO2) with a {001} facet was successfully prepared, and its bromate-removal activity under visible light was examined. The microstructure, morphology, and chemical state of the doping elements and the optical property of the photocatalysts were examined using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), photoluminescence spectroscopy (PLS), and UV-Vis diffuse reflectance spectra (DRS). The results indicate that the optical properties of F-Fe-TiO2 with the {001} facet and cuboid morphology were obviously improved and its photocatalytic activity was significantly enhanced. The bromate solution of 100 μg/L was thoroughly removed with 0.5 g/L dosage of 1.0% F- and 0.08% Fe-codoped TiO2 composite within 1 hour under visible light. [ABSTRACT FROM AUTHOR]

A series of three-dimensional ZnxCd1-xS/reduced graphene oxide (ZnxCd1-xS/RGO) hybrid aerogels was successfully synthesized based on a one-pot hydrothermal approach, which were subsequently used as visible-light-driven photocatalysts for photoreduction of Cr(VI) in water. Over 95% of Cr(VI) was photoreduced by Zn0.5Cd0.5S/RGO aerogel material within 140 min, and such photocatalytic performance was superior to that of other ZnxCd1-xS/RGO aerogel materials (x≠0.5) and bare Zn0.5Cd0.5S. It was assumed that the enhanced photocatalytic activity of Zn0.5Cd0.5S/RGO aerogel was attributed to its high specific surface area and the preferable synergetic catalytic effect between Zn0.5Cd0.5S and RGO. Besides, Zn0.5Cd0.5S/RGO aerogel materials were robust and durable enough so that they could be reused several times with merely limited loss of photocatalytic activity. The chemical composition, phase, structure, and morphology of Zn0.5Cd0.5S/RGO aerogel material were carefully examined by a number of techniques like XRD, SEM, TEM, BET, Raman characterizations, and so on. It was found that Zn0.5Cd0.5S/RGO aerogel possessed hierarchically porous architecture with the specific surface area as high as 260.8 m2 g−1. The Zn0.5Cd0.5S component incorporated in Zn0.5Cd0.5S/RGO aerogel existed in the form of solid solution nanoparticles, which were uniformly distributed in the RGO matrix. [ABSTRACT FROM AUTHOR]

Mineralogical basalt fibers as a complementary adsorbent were introduced to improve the adsorption of CO2 over the surfaces of photocatalysts. TiO2 photocatalysts (M-TiO2) incorporated with 5.0 mol.% 3d-transition metals (Fe, Co, Ni, and Cu) were prepared using a solvothermal method and mixed with basalt fibers for applications to CO2 photoreduction. The resulting 5.0 mol.% M-TiO2 powders were characterized by X-ray diffraction, scanning electron microscopy, ultraviolet-visible spectroscopy, photoluminescence, Brunauer, Emmett, and Teller surface area, and CO2-temperature-programmed desorption. A paste composed of two materials was coated and fixed on a Pyrex plate by a thermal treatment. The 5.0 mol.% M-TiO2/basalt fiber films increased the adsorption of CO2 significantly, indicating superior photocatalytic behavior compared to pure TiO2 and basalt fiber films, and produced 158~360 μmol gcat-1 L−1 CH4 gases after an 8 h reaction. In particular, the best performance was observed over the 5.0 mol.% Co-TiO2/basalt fiber film. These results were attributed to the effective CO2 gas adsorption and inhibition of photogenerated electron-hole pair recombination. [ABSTRACT FROM AUTHOR]

Hierarchical flower-like Bi2WO6 was successfully synthesized by facile hydrothermal method at low pH. And Ag/AgCl was loaded by photoreduction on its surface. As-prepared photocatalysts were characterized by various techniques. Bi2WO6 was successfully synthesized at a size of 2-3 μm. Depositing Ag/AgCl did not destroy the crystal structure, and both Ag+ and metallic Ag0 were found. The band gap of the composite was 2.57 eV, which indicates that visible light could be the activating irradiation. In the photocatalytic activity test, the composite with 10 wt% Ag/AgCl boasted the highest removal efficiency (almost 100%) in 45 min. The significant enhancement can be attributed to the surface plasmon resonance (SPR) effect and the establishment of heterostructures between Ag/AgCl and Bi2WO6. A possible mechanism of photocatalytic oxidation in the presence of Ag/AgCl-Bi2WO6 was proposed. This work sheds light on the potential applications of plasmonic metals in photocatalysis to enhance their activities. [ABSTRACT FROM AUTHOR]

TiO2-graphene (TiO2-RGO) nanocomposites were prepared via a simple chemical method by using graphene oxide (GO) and TiO2 nanoparticles as starting materials. The morphologies and structural properties of the as-prepared composites were characterized by X-ray diffraction, Raman spectroscopy, N2 adsorption-desorption measurements, and transmission electron microscopy. TiO2-RGO nanocomposites exhibited great photocatalytic activity toward reduction of CO2 into CH4 (2.10 μmol g−1 h−1) and CH3OH (2.20 μmol g−1 h−1), which is attributed to the synergistic effect between TiO2 and graphene. [ABSTRACT FROM AUTHOR]

A series of new two semiconductor catalysts, Co3O4/CeO2, were prepared by glycine-nitrate combustion method for photocatalytic reduction of carbon dioxide to produce methanol and ethanol under visible light (λ>400 nm) irradiation. The catalysts were characterized by BET, UV-vis spectra, XRD, SEM, PL, and XPS and the results indicated that the catalyst with 5 wt.% of Co3O4 has the highest yield among all kinds of tests with the methanol yield of 1.52 μmol·g−1·h−1 and the ethanol yield of 4.75 μmol·g−1·h−1, which are about 2.34 and 1.71 times as large as those of CeO2. However, methanol and ethanol can hardly be detected for Co3O4 under the same condition because of its too narrow band gap. The improvement of the photoreduction activity of Co3O4 doped CeO2 was caused by the separation of electron-hole pairs of Co3O4/CeO2 and charge transfer between Co3O4 and CeO2, mimicking the Z-scheme in photosynthesis. [ABSTRACT FROM AUTHOR]

This paper focuses on the synthesis of novel Ag nanoclusters (NCs) using DHLA as capping reagents in aqueous solution by a photoreduction method. Luminescence studies indicated that the DHLA-Ag NCs exhibited strong blue emission with maximum peak at 480 nm. The maximum emission of the NCs can be greatly improved with irradiating time by around 15-fold from 3 h to 67 h. By means of mycelium growth rate, the results showed that the Ag NCs with smaller sizes had a good antimicrobial effect. [ABSTRACT FROM AUTHOR]

Graphene oxide sheets suspended in ethanol interact with excited CdS nanoparticles and contributed to photocatalytic reduction by accepting electron from nanoparticle. The UV-Vis measurement showed that electrical absorbance of the CdS/graphene oxide sheets increased by decreasing the irradiation time and after 2 h it remained constant which indicates the optimum reduction time. Furthermore, the direct interaction between CdS nanoparticles and graphene sheets hinders the collapse of exfoliated sheets of graphene. The 4-point probe measurement of nanocomposite with different ratios of graphene oxide in CdS solution after irradiation shows that the conductivity of them increased by increasing the amount of GO, but further increasing causes incomplete photo reduction process due to exorbitance increasing GO sheets which contribute to decreasing the conductivity. The CdS/RGO composite material can be used as a gas sensor for CO2 based on its electrocatalytic behavior. The low-cost and easy fabrication sensor shows rapid response and high sensitivity. By varying the amount of GO the optimum concentration which shows high sensitivity is found and its good performance compared with other is attributed to its higher conductivity due to complete reduction. Moreover, the effects of thermal annealing on the conductivity of CdS/RGO film and the performance of devices are researched. [ABSTRACT FROM AUTHOR]

A type of iron-doped titania thin film was prepared by means of sol-gel method to degrade indoor formaldehyde (HCHO), ammonia (NH3), and benzene (C6H6) under sunlight. The photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Vis spectroscopy, and energy dispersive spetra (EDS). The results showed that the iron was doped in the TiO2 photocatalyst successfully. The absorption edge of doped TiO2 had red shifts and the doped TiO2 had a stronger absorption than the pure TiO2 in the visible region. Fe-doped TiO2 thin film prepared with the optimal preparation condition could remove indoor HCHO, NH3 and C6H6 effectively under solar light irradiation. The removal percentage of HCHO, NH3 or C6H6 after 9 h photocatalytic reaction under solar light reached 55%, 53.1%, and 37.5%, respectively, when they existed in the air individually. When the three pollutants were mixed in the air, the removal percentage decreased to 33.3%, 28.3%, and 28%. The degradation reaction of the three pollutants followed the pseudo first-order kinetics, which reflects that the photocatalytic reaction was controlled by the surface chemical reaction and the reaction rate was controlled by concentration of reactants. [ABSTRACT FROM AUTHOR]

Cu2+ ions were successfully loaded into TiO2 nanotubes using wet impregnation technique in 0.6 M Cu(NO3)2-3H2O solution. The effect of reaction temperatures on the nanotube's morphology, crystal structure, and their photocatalytic reduction of Pb(II) ions were investigated. The high reaction temperature could improve the crystallinity of anatase phase. However, irregular and corrugated nanotubular surface covered with Cu precipitates was observed. In the present study, incorporation of an optimum content of Cu element (1.3 at%) into TiO2 nanotubes at room temperature has an important function in enhancing the photocatalytic reduction of Pb(II) ions in alkaline condition (pH 11) due to the higher synergistic effects of photocatalytic reaction under UV illumination. The optimum concentration of Pb(II) ions for effective Pb(II) ions removal performance was found in between 20 and 60 ppm. [ABSTRACT FROM AUTHOR]

Lotus-type porous copper with long cylindrical pores aligned parallel to the solidification direction was studied for use as an antibacterial material. The antibacterial performance of lotus-type porous copper samples with different specific surface areas against Escherichia coli was investigated. The results confirmed that the antibacterial effect gradually increased with specific surface area. The correlation between the pore structure of lotus-type porous metals and their antibacterial effect was also analyzed in detail. Our research proposes a new application of these metals in the water purifying system. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (g-C3N4) was synthesized at 520°C by the pyrolysis of cyanamide, dicyandiamide, and melamine. The samples were characterized by X-ray diffraction (XRD), UV-visible diffuse reflectance spectra, Fourier transform infrared spectroscopy (FT-IR), and elemental analyzer. The photocatalytic activity of g-C3N4 was evaluated by the photodegrading experiments of methylene blue (MB). The results indicated that g-C3N4 obtained from dicyandiamide exhibited higher activity, and the higher C/N molar ratio and degree of condensation increase the photocatalytic activity of g-C3N4. A photocatalytic mechanism presumed the MB photodegradation over the C3N4 photocatalyst is attributed to photogenerated electron impelled multistep reduction of O2. [ABSTRACT FROM AUTHOR]

Photocatalytic decomposition of methyl red (MR) as a pollutant in wastewater samples is investigated in this study. This photo degradation was investigated in water in neutral, alkaline, and acidic media under external UV light irradiation by zinc oxide nanosized catalysts on granule glass. The effect of four atmosphere types including air, nitrogen, oxygen, and argon was investigated. Finally, it was found that photodecomposition using nanosized ZnO layered on glass is a new alternative route for efficient wastewater treatment. The results showed that the titled dye is degraded by various rate under different atmosphere and pH. [ABSTRACT FROM AUTHOR]

Nitrogen-doped TiO2 powders have been prepared using technical guanidine hydrochloride, titanyl sulfate, and urea as precursors via a mild hydrothermal method under initial pressure of 3MPa,150°C holding for 2h without any postheat treatment for crystallization. The nanocrystalline N-doped TiO2 powders were composed of anatase TiO2 by XRD. The grain size was estimated as about 10 nm, and the BET specific surface area of the powder was measured as 154.7 m²/g. The UV-visible absorption spectra indicated that the absorption edge of the N-doped TiO2 powders had been red shifted into the visible light region. The photocatalytic performance of the synthesized powders was evaluated by degradation of phenol under visible light irradiation. And the effects of the catalyst load and the initial pH value on the photodegradation were also investigated. [ABSTRACT FROM AUTHOR]

Na2Ti6O13/TiO2 composite particles were synthesized through the hydrolyzation of tetrabutyl titanate in a reverse microemulsion and characterized by thermogravimetry and differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), and scanning electron microscope (SEM). The photocatalytic property of Na2Ti6O13/TiO2 was evaluated by degradation of 2,4- dichlorophenol(2,4-DCP) under 40W ultraviolet lamp (λ = 365 nm) irradiation and compared with commercial P25-TiO2 in the same condition. The results showed that the synthesized nanobelts Na2Ti6O13/TiO2 heterostructures had typical width from 80 to 100 nm, with thickness less than 40 nm and length up to 5 µm. Such Na2Ti6O13/TiO2 nanosized particles exhibited better photocatalytic activity than that of P25-TiO2, and the degradation rate of 2,4-DCP with initial concentration of 0.02 g/L reached 99.4% at the end of 50 min. [ABSTRACT FROM AUTHOR]

The removal of bisphenol A (BPA) under simulated solar irradiation and in the presence of either TiO2 or ZnO catalysts immobilized onto glass plates was investigated. The effect of various operating conditions on degradation was assessed including the amount of the immobilized catalyst (36.1-150.7 mg/cm² for TiO2 and 0.5-6.8 mg/cm² for ZnO), initial BPA concentration (50-200 µg/L), treatment time (up to 90 min), water matrix (wastewater, drinking water, and pure water), the addition of H2O2 (25-100 mg/L), and the presence of other endocrine disruptors in the reaction mixture. Specifically, it was observed that increasing the amount of immobilized catalyst increases BPA conversion and so does the addition of H2O2 up to 100 mg/L. Moreover, BPA degradation follows first-order reaction kinetics indicating that the final removal is not practically affected by the initial BPA concentration. Degradation in wastewater is slower than that in pure water up to five times, implying the scavenging behavior of effluent's constituents against hydroxyl radicals. Finally, the presence of other endocrine disruptors, such as 17α-ethynylestradiol, spiked in the reaction mixture at low concentrations usually found in environmental samples (i.e., 100 µg/L), neither affects BPA degradation nor alters its kinetics to a considerable extent. [ABSTRACT FROM AUTHOR]

In this work, the nanostructured anatase mesoporous membranes were prepared for water ultrafiltration (UF) process with photocatalytic and physical separation capabilities. A macroporous substrate was synthesized from α-Al2O3, then a colloidal titania sol was used for the preparation of the intermediate layer. Also, the membrane top layer was synthesized by deposition and calcination of titania polymeric sol on the intermediate layer. The characterization was performed by DLS, TG-DTA, XRD, BET, FESEM, TEM, and AFM techniques. Also, the filtration experiments were carried out based on separation of methyl orange fromaqueous solution by a membrane setup with a dead-end filtration cell. Photocatalytic activity of themembranes was evaluated by methyl orange photodegradation using UV-visible spectrophotometer. The mean particle size of the colloidal and polymeric sols was 14 and 1.5 nm, respectively. The anatase membranes exhibited homogeneity, with the surface area of 32.8m2/g, the mean pore size of 8.17 nm, and the crystallite size of 9.6 nm. The methyl orange removal efficiency by the mesoporous membrane based on physical separation was determined to be 52% that was improved up to 83% by a coupling photocatalytic technique. Thus, the UF membrane showed a high potential due to its multifunctional capability for water purification applications. [ABSTRACT FROM AUTHOR]

We evaluated the use of Fenton reactions induced by solar radiation in the treatment of effluent from a factory of paints for buildings, after prior removal of the suspended solids. The increase of H2O2 concentration from 100 to 2500?mg?L-1 for a [Fe2+] = 105?mg?L-1 contributed to the reduction of DOC, COD, and toxicity. Our best results were achieved using 1600?mg?L-1 H2O2, with 90% of DOC and COD removal and a complete removal of the toxicity with respect to Artemia salina. Additionally, through increasing Fe2+ concentration from 15 to 45?mg?L-1, the DOC removal rate increased 11 times, remaining almost constant in the range above 45 until 105?mg?L-1. Under our best experimental conditions, 80% of DOC removal was achieved after an accumulated dose of 130?kJ?m-2 of UVA radiation ( ?min of solar irradiation under an average UVA irradiance of ?W?m-2), while 40% of DOC removal was reached after 150?min under only thermal Fenton reactions. The results suggest the effectiveness of implementation of solar photo-Fenton process in the decontamination and detoxification of effluents from factories of paints for buildings. [ABSTRACT FROM AUTHOR]

Phosphotungstic acid (HPW)-impregnated yeast hybrid microspheres were prepared by impregnation-adsorption technique through tuning pHof the aqueous yeast suspensions. The obtained products were characterized by field emission scanning electron microscopy (FE-SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD), thermogravimetry-differential scanning calorimetry (TG-DSC), and ultraviolet-visible spectrophotometry (UV-Vis), respectively. FE-SEM and EDS ascertain that the HPW has been effectively introduced onto the surface of yeast, and the resulting samples retain ellipsoid shape, with the uniform size (length 4.5 ± 0.2 µm, width 3.0 ± 0.3 µm) and good monodispersion. XRD pattern indicates that the main crystal structure of assynthesized HPW@yeast microsphere is Keggin structure. TG-DTA states that the HPW in composites has better thermal stability than pure HPW. Fourier transforminfrared spectroscopy (FT-IR) elucidates that the functional groups or chemical bonds inherited from the pristine yeast cell were critical to the assembling of the composites. UV-Vis shows that the obtained samples have a good responding to UV light. The settling ability indicates that the hybrid microspheres possess an excellent suspension performance. In the test of catalytic activity, the HPW@yeast microsphere exhibits a high photocatalytic activity for the decoloration of Methylene blue and Congo red dye aqueous solutions, and there are a few activity losses after four cycles of uses. [ABSTRACT FROM AUTHOR]

Fe-TiO2 supported on spherical activated carbon (Fe-TiO2/SAC) with different Fe contents was prepared by heat treatment process after ion exchange method. The prepared Fe-TiO2/SAC was characterized by SEM, EDS, and BET. Batch experiments for photocatalytic degradation of humic acid by Fe-TiO2/SAC were carried out in the fluidized bed photoreactor. It was found that 0wt% Fe-TiO2/SAC had high photocatalytic activity in the wavelength range of 100~280 nm. However, Fe-TiO2/SAC with Fe contents of 0.4, 0.6, and 0.8 wt% exhibited higher photocatalytic activity than 0 wt% Fe-TiO2/SAC in the wavelength range of 315~400 nm compared to that of 100~280 nm. The optimum Fe content was 0.6 wt% for maximum photocatalytic degradation of humic acid. Moreover, Fe-TiO2/SAC does not require an additional process step for separation of photocatalyst from treated water after photocatalysis. [ABSTRACT FROM AUTHOR]

The photocatalytic degradation of methyl violet using TiSiW12O40/TiO2 as a novel eco-friendly catalyst under simulated natural light irradiation was investigated. The physical characterizations were carried out by TG/DTA, FT-IR, XRD, andUV-visible spectra. The effects of the initial methyl violet concentration, the solution pH, and catalyst dosage on the photocatalytic degradation rate of methyl violet were also examined. The results demonstrated that at optimal condition (initial concentration of methyl violet is 20mg/L, catalyst dosage is 0.3 g, and the pH is 5.5), the degradation rate of methyl violet is as high as 82.4% after 3 h under simulated natural light irradiation. The reaction of photocatalysis for methyl violet can be expressed as first-order kinetic model. [ABSTRACT FROM AUTHOR]

Mesoporous Au-TiO2 nanocomposite plasmonic photocatalyst with visible-light photoactivity was prepared by a simple spray hydrolytic method using photoreduction technique at 90°C. The prepared samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and N2 adsorption-desorption isotherms. The formation of hydroxyl radicals (• OH) on the surface of visible-light illuminated Au-TiO2 nanocomposites was detected by the luminescence technique using terephthalic acid as probe molecules. The photocatalytic activity was evaluated by photocatalytic decolorization of Rhodamine-B (RhB) aqueous solution under visible-light irradiation (λ > 420 nm). The results revealed that the TiO2 could be crystallized via spray hydrolysis method, and the photoreduction technique was facilitated to prepare Au nanoparticles in the mesoporous TiO2 at 90°C. The light absorption, the formation rate of hydroxyl radicals, and photocatalytic decolorization of Rhodamine-B aqueous solution were significantly enhanced by those embedded Au nanoparticles in the Au-TiO2 nanocomposites. The prepared Au-TiO2 nanocomposites exhibit a highly visible-light photocatalytic activity for photocatalytic degradation of RhB in water, and their photocatalytic activity is higher than that of the pristine TiO2 nanoparticles due to the surface plasmon resonance. [ABSTRACT FROM AUTHOR]

The simultaneous photocatalytic reduction of Cr(VI) and oxidation of benzoic acid (BA) in aqueous suspensions using N-Fcodoped TiO2 and simulated solar irradiation were investigated in the present study. Chemometric optimization tools such as response surface methodology (RSM) and experimental design were used to model and optimize selected operational parameters of the simultaneous photocatalytic reduction of Cr(VI) and oxidation of BA. RSM was developed by considering a central composite design with three input variables, that are, N-F-codoped TiO2 mass, ratio of Cr/BA, and pH. The removal of Cr(VI) and BA in binary systems, containing both Cr(VI) and BA, showed a synergistic photocatalytic decontamination as BA significantly facilitated Cr(VI) reduction, whereas Cr(VI) accelerated also BA degradation. Due to the anionic-type adsorption onto TiO2 and its acid-catalyzed photocatalytic reduction, the removal of Cr(VI) decreased with increasing pH, while the degradation of BA followed also the same trend. Under the optimum conditions (N-F-TiO2) = 600 mg L-1, ratio of Cr(VI)/BA = 5, pH = 4, the removal for both Cr and BA followed a pseudo first-order kinetic model. It was found that the selected variables have significant effect both on Cr(VI) removal and BA degradation efficiency. The results revealed the feasibility and the effectiveness of using N-F-codoped TiO2 as photocatalyst for simultaneous decontamination of Cr(VI) and organic pollutants such as BA due to the appropriate oxidation and reduction ability of the photogenerated hVB+ -eCB- pairs. [ABSTRACT FROM AUTHOR]

This study discussed the photoreduction of Cr(VI) ions in aqueous solutions by UV/TiO2 photocatalytic processes under various operational factors. Experimental results showed that the removal rate of Cr(VI) increased with decreasing solution pH values and with increasing dosages of organic compounds, indicating that the recombination rate of electrons and h+ can be retarded in the reaction systems by the addition of the scavenger, thus raising the reaction rate of Cr(VI). The relationship of the chemical reaction rate of Cr(VI), TiO2 dosage, and changes of Cr(VI) concentration was expressed by the pseudo-first-order kinetic equation. Comparing the experimental results of two different doping metals in modified TiO2 photoreduction systems, the removal rate of Cr(VI) by the Ag/TiO2 process is larger, possibly because the electron transferring ability of Ag is superior to that of Cu. However, the photoreduction rates of Cr(VI) by modified UV/TiO2 processes are worse than those by a nonmodified commercial UV/TiO2 process. [ABSTRACT FROM AUTHOR]

Titanium dioxide was surface-modified by grafting vanadyl species using vanadyl triisopropoxide as a precursor. The resulting material, (VOx)n/TiO2, was characterized by Raman spectroscopy and photoelectrochemical methods. Photocatalytic oxidation of benzyl alcohol and cyclohexene were used to test oxidation selectivity and 4-nitro-benzaldehyde to assess selective photoreduction. The surface-modified TiO2 exhibits an enhanced selectivity to benzaldehyde in the photocatalytic oxidation of benzyl alcohol in an aqueous medium and an increase of cyclohexenol formation in the case of cyclohexene in nonaqueous solvent. The salient result is the 100% selective reduction of the nitrogroup in 4-nitro-benzaldehyde achieved under mild experimental conditions. [ABSTRACT FROM AUTHOR]

Titanium dioxide/silver (TiO2/Ag) composite films were prepared by incorporating Ag in pores of mesoporous TiO2 films using a photoreduction method. The Ag nanoparticle sizes were in a range of 4.36-38.56 nm. The TiO2/Ag composite films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The TiO2 and TiO2/Ag composite films were then sensitized by immersing in a 0.3mM N719 dye solution and fabricated for conventional dye-sensitized solar cells (DSCs). J-V characteristics of the TiO2/Ag DSCs showed that the Ag nanoparticle size of 19.16nm resulted in the short circuit current density and efficiency of 8.12 mA/cm² and 4.76%. [ABSTRACT FROM AUTHOR]