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In the study, a novel approach of Cu, Co tuned photocatalyst β-SiC catalyze hydrolysis of ammonia borane was proposed as a means to boost H2 evolution. Electronic properties including band structure and DOS of β-SiC and CuCo/β-SiC are calculated. In addition, the hydrolysis mechanism of AB and photocatalytic boosting mechanism of AB hydrolysis on the catalyst CuCo/β-SiC are discussed. The systematic investigation showed that the transition metal atom (Cu, Co) can tune the electronic properties of the β-SiC, and reduce the band gap of semiconductor catalyst β-SiC from the value of 2.739eV–0.535eV. Which makes the β-SiC response to the wider UV–Vis spectrum, and transition metal atom (Cu, Co) tuned β-SiC can help to boost the photocatalytic quantum efficiency of photocatalytic AB hydrolysis reaction. In the process of CuCo/β-SiC catalyzed AB hydrolysis, the reaction path can be described in three key steps: At first, CuCo/β-SiC bond to B of AB, induce the B H bond activation, then H3B- attacked by a H2O molecule, which contributes to the concerted dissociation of B N bond. Finally, via BH3 hydrolysis and produce the borate ion accompanied by the H2 produce. In the reaction of AB hydrolysis, the reaction barrier step is the step of H2O molecule attack BH3, and its energy barrier is 31.44 kcal/mol. In addition, the synergistic hydrolyze and photolyze AB to H2 evolution mechanism was first proposed due to AB can be photocatalyzed by semiconductor photocatalyst β-SiC and conventional catalyzed by the metal catalyst.

Titanium dioxide (TiO2) is considered as an inert and safe material and has been used in many applications for decades. TiO2 have been widely studied, due to its interesting general properties in a wide range of fields including catalysis, antibacterial agents, in civil as nano-paint (self-cleaning) and especially photocatalysis, and that affect the quality of life. Thus, the development of nanotechnologies TiO2 nanoparticles, with numerous novel and useful properties, are increasingly manufactured and used. TiO2 doped with noble metal are good candidates in the performance these applications. The fascinating physical and chemical features of TiO2 depend on the crystal phase, size and shape of particles. For example, varying phases of crystalline TiO2 have different band gaps that rutile TiO2 of 3.0 eV and anatase TiO2 of 3.2 eV, determine the photocatalytic performance of TiO2. This chapter explains basic information on TiO2 and theoretical concepts of nanostructure of TiO2 nanoparticles as a semiconductor photocatalyst.

In this work, taking graphitic carbon nitride (g-C3N4) as an example, the synergistic utilization of the advantages of two-dimensional (2D) structure and heteroatom modification is realized. To better understand the role of such structure tailoring, the complicated photocatalytic reaction involving multiple small molecules, namely NO removal, is selected to serve as a model reaction. The experimental results find that the 2D g-C3N4 with oxygen modification (2D OCN) exhibits enhanced performance with good stability in photocatalytic NO removal compared to pristine g-C3N4, as a result for the improved charge separation and optimized molecular adsorption. On one hand, the 2D structure of OCN can shorten the charge migration distance, endow the semiconductor improved redox ability and provide large specific area for reaction proceeding. On the other hand, the oxygen modification could optimize the adsorption ability of reaction molecules (NO and O2) benefiting the surface catalytic reaction. All the merits mentioned above are supported by detailed characterization and theoretical calculation. This article presented here provides a case study for designing efficient photocatalyst and an approach to analyze the correlation between structure and performance.

Photocatalytic overall water splitting (OWS) in a stoichiometric ratio has attracted increasing attention for the realization of a sustainable, environmentally friendly future. However, this reaction exhibits sluggish kinetics due to efficiency limitations of the involved steps, including photon absorption, electron transfer, and the reactions that occur at triple-phase boundary regions. Herein, we report a general multiscale strategy to address this challenge by designing a model composite catalyst with a high loading density of isolated Bi0.5Y0.5VO4 nanocrystals, as building blocks, dispersed in a hexagonally ordered mesoporous silica matrix. In contrast to the well-recognized heterojunction formed between different semiconductors, we show that confined growth favours the formation of isolated quaternary solid-solution photocatalysts (Bi0.5Y0.5VO4), which can further interface with the insulating silica to overcome temperature limitations and exhibit enhanced photon absorption and electrochemical and mass transfer properties due to the transparent periodic porous structure of silica and the as-formed small nanocrystals with high crystallinity and a passivated surface. When the semiconductor photocatalyst is incorporated with the inert silica insulator, this nanoarchitecture does not inhibit the OWS activity but actually delivers a 10-fold higher OWS activity than bulk Bi0.5Y0.5VO4 prepared by the conventional solid-state method.

This work explores the critical role of NiO co-catalyst assembled on the surface of a CuS primary photocatalyst which effectively improves interface properties and enhances solar-to-hydrogen production by prolonging lifetime of photo-excitons generated at the CuS surface. The nanoscale CuS/NiO heterojunction is formulated using hydrothermal and wet impregnation methods. The resultant CuS/NiO composite shows optical absorbance between 380 and 780 nm region. The type-II energetic structure formed at CuS/NiO heterojunction facilitates rapid charge separation and as a result, the CuS/NiO composite exhibits 13 folds higher photocatalytic water splitting performance than CuO and NiO. The champion CuO/NiO photocatalyst is first identified by screening the catalysts using a preliminary water splitting test reaction under natural Sunlight irradiation. After the optimization of the catalyst, it was further explored for enhanced photocatalytic hydrogen production using different organic substances dispersed in water (alcohols, amine and organic acids). The champion CuS/NiO catalyst (CPN-2) exhibited the photocatalytic hydrogen production rate of 52.3 mmol h−1.g−1cat in the presence of lactic acid-based aqueous electrolyte and, it is superior than hydrogen production rate obtained in the presence of other organic substances (triethanolamine, glycerol, ethylene glycol, methanol) tested under identical experimental conditions. These results indicate that the energetic structure of CuS/NiO photocatalyst is favorable for photocatalytic oxidation or reforming of lactic acid. The oxidation of lactic acid contributes both protons and electrons for enhanced hydrogen generation as well as protects CuS from photocorrosion. The modification of surface property and energetic structure of CuS photocatalyst by the NiO co-catalyst improves photogenerated charge carrier separation and in turn enhances the solar-to-hydrogen generation efficiency. The recyclability tests showed the potential of CPN-2 photocatalyst for prolonged photocatalytic hydrogen production while continuous supply of lactic acid feedstock is available.

Ground and distilled water-mediated tungsten trioxide (WO3) nanostructures are prepared via hydrothermal approach. The physical and surface chemical properties of catalyst are analyzed using XRD, SEM-EDAX, HR-TEM, FT-IR, UV-DRS, Zeta potential and photoluminescence spectroscopy. It is confirmed that ground water has high impacts on the materials properties such as crystallinity and morphology. HR-TEM results proved the transformation of single crystalline to polycrystalline for sample W1 and W3 respectively. The photocatalytic efficiency of the various catalyst was analyzed by the degradation of methylene blue as a probe dye-molecule which was monitored by UV-vis spectroscopy. The decolorization efficiency was observed as 1.14 times maximized in distilled water prepared catalyst when compared with ground water prepared catalyst. Moreover, the persulfate activation was found as 2.3 fold amplified in distilled water prepared catalyst when compared with other catalyst. On the development of various water-assisted WO3 semiconductor photocatalysis, this work can provide new insights into the design of novel photocatalyst for potential applications in the energy and environmental remediation sectors.

In this study, we demonstrate that pinched hysteresis can be used as a regenerative marker for the commonly used semiconductor-based photocatalyst such as Molybdenum disulfide, Tin oxide, Zinc oxide, and its composites. The degradation studies in this work reveal that the photocatalyst exhibiting pinched hysteresis characteristics in the dual sweep current-voltage measurement has poor regeneration capabilities. Also, the transport properties of these photocatalysts have a striking similarity to the Grotthuss mechanism with surface adsorbed water playing a dominant role. This in-turn induced quenching of UV photoresponse in the photocatalyst and the degradation time increased with each irradiation cycle. In the photocatalyst having no pinched hysteresis characteristics, stable UV photoresponse was observed and the photocatalytic activity persisted up to 9 irradiation cycles. Our studies reveal that pinched hysteresis can be used as a reliable marker to determine the regenerative properties of a photocatalyst.

Gaseous oxides generated during industrial processes, such as carbon oxides (COx) and nitrogen oxides (NOx), have important effects on the Earth’s atmosphere. It is highly desired to develop a low-cost and efficient route to convert them to harmless products. Here, direct splitting of gaseous oxides was proposed on the basis of photocatalysis by an amorphous oxide semiconductor. As an example, splitting of CO2 into carbon and oxygen was achieved over amorphous zinc germanate (α-Zn-Ge-O) semiconductor photocatalyst under 300 W Xe lamp irradiation. Electron paramagnetic resonance and 18O isotope labeling indicated that the splitting of CO2 was achieved via photoinduced oxygen vacancies on α-Zn-Ge-O reacting and thus filling with O of CO2, while the photogenerated electrons reduced the carbon species of CO2 to solid carbon. Under irradiation, such a defect reaction is sustainable by continuous photogenerated hole oxidation of surface oxygen atoms on α-Zn-Ge-O to form oxygen vacancies and to release O2. When ...

A tandem reaction system consisting of a photocatalyst (Pt/TiO 2 ) and a nonphotocatalyst (SnPd/Al 2 O 3 ) promoted the reduction of NO 3 − into gaseous products (mainly N 2 ) under light irradiation (λ > 300 nm) in the presence of glucose as a hole scavenger. Photocatalytic H 2 evolution (2H + + 2 e − → H 2 ) proceeded over Pt/TiO 2 , and conventional catalytic reduction of NO 3 − with H 2 (NO 3 − + 5/2H 2 → 1/2N 2 + 2H 2 O + OH − ) occurred over SnPd/Al 2 O 3 . We optimized the loading amount of Pt on TiO 2 , the Sn/Pd ratio, the loading amount of SnPd on Al 2 O 3 , and the two catalyst dosages. The optimized tandem system gave a high reduction rate of NO 3 − and a high selectivity for gas (94%) from the photocatalytic reduction of NO 3 − in water. On the other hand, a typical semiconductor photocatalyst SnPd/TiO 2 with an optimized Sn/Pd ratio and an optimized loading amount of SnPd bimetal on TiO 2 reduced NO 3 − about two-thirds as fast as the tandem system and was less selective for gas (70%). The tandem system suppressed the wasted H 2 formation, resulting in high light use efficiency for the NO 3 − reduction (95%), which is defined as the ratio of the number of electrons consumed for NO 3 − reduction to the total number of electrons consumed for both NO 3 − reduction and photocatalytic H 2 evolution, though the tandem and SnPd/TiO 2 systems consumed about the same total number of electrons. The tandem system has two advantages: (i) the Pt/TiO 2 and SnPd/Al 2 O 3 subsystems can be separately designed to give highly efficient photocatalytic and catalytic reactions, respectively; and (ii) the reaction rates of photocatalytic and catalytic reactions can be easily controlled by changing the catalyst dosage in the reactor. Those advantages brought about a high reduction rate for NO 3 − , high selectivity for gas, and high light use efficiency for NO 3 − reduction in the photocatalytic reduction of NO 3 − in water.

The synergistic combination of a heterogeneous organic semiconductor mesoporous graphitic carbon nitride (mpg-CN) and a homogeneous nickel catalyst with visible light irradiation at room temperature affords the C(sp2)−C(sp3) cross coupling of aryl halides and potassium alkyl trifluoroborates by single electron transmetallation. Like the homogeneously catalysed protocol, the reaction is compatible with a variety of functional groups including electron donating and electron withdrawing aryl and heteroaryl moieties. Moreover, this protocol allows the installation of allyl groups enlarging the scope of the method. The heterogeneous mpg-CN photocatalyst is easily recovered from the reaction mixture and for several times reused paving the way for larger scale industrial applications of this type of photocatalytic bond forming reactions.

The Ta3N5 semiconductor photocatalyst possesses a 720 nm (about 1.72 eV) sub-band-gap optical absorption but the mechanism of this optical absorption is still controversial. In this study, the hybrid density functional theory calculations are performed to unravel the mechanism of 720 nm sub-band-gap optical absorption of Ta3N5. By studying the possible optical absorption initiated by the ON impurity and the VN defect, we find that the 720 nm sub-band-gap optical absorption of Ta3N5 may be ascribed to the electron transition from V(·)(N) to V(···)(N). In addition, we propose that the 720 nm sub-band-gap optical absorption can be used to qualitatively evaluate the photocatalytic water splitting ability of Ta3N5.

Although the crystallographic space group has been determined, detailed first principles calculations of the LaTiO2N semiconductor photocatalyst crystal have not been performed because of the nitrogen/oxygen sosoloid-like anion distribution. In this study, based on the Heyd-Scuseria-Ernzerhof method and experimental anion content, we present the possibility of determining detailed information about the LaTiO2N sosoloid-like anion distribution by dividing the anions into possible primitive cells. The detailed information about the anion distribution based on the characteristics of the energetically acceptable primitive cell structures suggests that the LaTiO2N structure is composed of aperiodic stacks of six building-block primitive cells, the non-vacancy primitive cells are located at the surface as effective photoreaction sites, and vacancy structures are located in the bulk. The surface oxide-rich structures increase the near-surface conduction band minimum rise and strengthen photoelectron transport to the bulk, while the content of the bulk vacancy structures should be balanced because of being out of photoreactions. This study is expected to provide a different perspective to understanding the LaTiO2N sosoloid-like anion distribution.

A novel Sr2CuInO3S oxysulfide p-type semiconductor photocatalyst has been prepared by solid state reaction method and it exhibits intriguing visible light absorption properties with a bandgap of 2.3 eV. The p-type semiconductor character of the synthesized Sr2CuInO3S was confirmed by Hall efficient measurement and Mott-Schottky plot analysis. First-principles density functional theory calculations (DFT) and electrochemical measurements were performed to elucidate the electronic structure and the energy band locations. It was found that the as-synthesized Sr2CuInO3S photocatalyst has appreciate conduction and valence band positions for hydrogen and oxygen evolution, respectively. Photocatalytic hydrogen production experiments under a visible light irradiation (λ>420 nm) were carried out by loading different metal and metal-like cocatalysts on Sr2CuInO3S and Rh was found to be the best one among the tested ones.

Solar irradiation spectrum on the earth consists of about 50% infrared energy, which has not used effectively in chemical storage and conversion into hydrogen via photocatalytic route. In this work, we reported the catalytic hydrogen generation over a photocatalyst consisting of semiconductor CdS and an up-conversion component NaYF4-Yb3+-Er3+(NYF) under infrared light irradiation. Under 980 nm laser irradiation, the input infrared light was up-converted into visible light, which was used to excite CdS to produce hydrogen and oxygen. The isotope experiments confirmed both of hydrogen and oxygen were produced from water. The highest hydrogen evolution rate of 3.38 μmol g−1 h−1 has been achieved. 0.008% of AQE under NIR light irradiation has been approached.

Oxygen is a natural impurity in the Ta3N5 semiconductor photocatalyst and very difficult to be completely eliminated in different growth conditions. In this study, density functional theory calculations are performed to unravel the cause of natural existence of oxygen impurity in Ta3N5 from the perspectives of mechanical stability and atomic cohesion. The elastic properties calculations show that the oxygen impurity in Ta3N5 is able to remedy the weakened mechanical stability induced by the nitrogen vacancy in Ta3N5. The atomic cohesion calculations show that the oxygen impurity in Ta3N5 enlarges the valence band width of Ta3N5, suggesting that the oxygen impurity is able to strengthen the atomic cohesion of Ta3N5. Based on our calculation results, we propose that the charge-compensation codoping is a promising strategy to improve the water splitting ability of Ta3N5 and simultaneously maintain the mechanical stability and enhanced atomic cohesion of Ta3N5.

Photocatalytic reduction of NO3- under UV irradiation in the presence of ethanol was carried out in the presence of semiconductor photocatalyst Pt/TiO2 and supported bimetallic non-photocatalyst Sn-Pd/Al2O3, which were dispersed in water. This system effectively and selectively promoted the photocatalytic reduction of NO3- to N2, whereas Pt/TiO2 or Sn-Pd/Al2O3 alone showed no or little activity under the reaction conditions. The decomposition rate of NO3- and selectivity to gaseous nitrogen compounds (mainly N2) for the present photocatalytic system were higher than those for TiO2 photocatalyst directly-modified with Sn-Pd particles.

The possibility of the direct electron transition between the donor/acceptor level generated by adsorbed molecules and the conduction/valence band for photo-illuminated semiconductor-type metal oxide is discussed. The effective wavelength is shifted to a longer wavelength by the formation of donor/acceptor level derived from adsorbed molecule (called here “in situ doping”). This photo-activation mechanism by “in situ doping” gives us attractive ways for the removing the limit of band-gap energy, and the utilization of visible light.

This research aims to investigate the process of forming a multi-scale copper oxide semiconductor (CuO/Cu2O) through a process of calcining a copper plate. The changes that occur during the formation of the oxide are thermally and surface evaluated. Evaluation using Differential Thermal Analysis (DTA) obtained by surface change of copper plate happened at temperature 380°C. Calcination of oxide formation was carried out at temperature 380°C for 1 hour. Surface evaluation process by using Scanning Electron Microscope (SEM) surface and cross-section, to determine diffusion of oxide formation on copper plate. The material composition is monitored by XRF and XRD to explain the process of structural and physical changes of the copper oxide plate formed during the heating process. The thickness of Cu plates used is 200-250 μm. SEM analysis results, the oxygen atom interruption region is in the range of 20-30 μm, and diffuses deeper during thermal oxidation process. The maximum diffusion depth of oxygen atoms reaches 129 μm.

The photocatalytic activity and physical properties on WO3 photocatalysts prepared by various methods were investigated. WO3 photocatalyst (WO3(PA)) prepared from aged amorphous peroxo-tungstic acid showed the highest activity for hexane degradation, which was ∼6 times higher than that of commercial WO3, and exhibited a strong absorption in visible light region. WO3(PA) loaded with CuO as co-catalyst showed a high activity for the complete oxidation of various organic compounds into CO2, as compared with the activities of commercial or homemade WO3 catalysts and N-doped TiO2. The high activity of WO3(PA) was explained by high surface area, good crystallinity, and efficient light absorption in visible light region. The light absorption of WO3(PA) powder was probably improved because of a decrease in surface reflection at the smooth and porous surface of WO3(PA) and because of its increased light path length.

Photocatalytic decoloration kinetics of triazine (Reactive Red 11, Reactive Red 2, and Reactive Orange 84) and vinylsulfone type (Reactive Orange 16 and Reactive Black 5) of reactive dyes have been studied spectrophotometrically by following the decrease in dye concentration with time. At ambient conditions, over 90-95% decoloration of above dyes have been observed upon prolonged illumination (15 h) of the reacting system with a 150 W xenon lamp. It was found that the decoloration reaction followed first-order kinetics. The values of observed rate constants were found to be dependent of the structure of dyes at low dye concentration, but independent at higher concentration. It also reports for the first time the decoloration of two different dyes together in a binary dye mixture using visible light-irradiated TiO(2) photocatalyst. Rate of decoloration of two different dyes together in a binary dye mixture using visible light-irradiated TiO(2) photocatalyst is governed by the adsorptivity of the particular dye onto the surface of the TiO(2) photocatalyst.

We report three new series of solid photocatalysts with different crystal structure: Bi2MNbO7 ( M = Al 3+ , Ga 3+ and In3+); A2B2O7 pyrochlore-type with cubic system and space group Fd3m; InMO 4 ( M = Nb 5+ , Ta 5+ ) : ABO4 wolframite-type with monoclinic system and space group P2/a and BiMO 4 ( M = Nb 5+ , Ta 5+ ) : ABO4 stibotantalite-type with triclinic system and space group P1(M=Ta) and orthorhombic systems with space group Pnna (M=Nb), respectively. Although the photocatalysts crystallize in the different crystal structure, they contain the same octahedral TaO6 and/or NbO6 in the different photocatalysts. The band structure of the photocatalysts is defined by Ta / Nb d -level and O 2p-level. The band gaps of the photocatalysts were estimated to be between 2.7 and 2.4 eV . Under visible light (λ>420 nm ) or ultra-violet irradiation, these photocatalysts were found to split water into H2 and/or O2. The photocatalytic activity increases significantly by loading co-catalysts on the surface of the photocatalyst, such as NiO and Pt.

Herein, Cu 2O spheres were prepared and encapsulated with reduced graphene oxide (rGO). The Cu 2O–rGO–C3N4 composite covered the whole solar spectrum with significant absorption intensity. rGO wrapped Cu 2O loading caused a red shift in the absorption with respect to considering the absorption of bare C3N4. The photoluminescence study confirms that rGO exploited as an electron transport layer at the interface of Cu 2O and C3N4 heterojunction. Utmost, ∼2 fold synergistic effect was achieved with Cu 2O–rGO–C3N4 for the photocatalytic reduction of 4-nitrophenol to 4-aminophenol in comparison with Cu 2O–rGO and C3N4. The Cu 2O–rGO–C3N4 photocatalyst was reused for four times without loss in its activity. SERB/SR/FT/CS-127/2011

Photochemical hydrogen production from a water-methanol mixture dispersed with a semiconductor photocatalyst, platinized titania (anatase) Pt/TiO 2 , is described. On the basis of the experimental hydrogen evolution rates under various conditions and morphologies of catalysts, some factors affecting the activity of the catalyst and the morphology of the catalyst, which maintains a high rate of the hydrogen evolution over a long period of time, are discussed

In view of this, we investigated new visible light nanostructured semiconductor photocatalyst especially in the field of composite metal oxide photocatalyst for solar hydrogen production from H 2 S. For this purpose, two methodologies using a quantum mechanical material design and the microscopic surface analysis on a nanometer scale are adopted. The catalysts are synthesized by our proprietary soft chemical approaches. Also, a demonstrative reaction system for the effective solar hydrogen production is presented.

A template- and surfactant-free process, thermally assisted photoreduction, is developed to prepare vertically grown ultra-long Pt nanowires (NWs) (about 30-40 nm in diameter, 5-6 μm in length, and up to 80 NWs/100 μm2 in the wire density) on TiO2 coated substrates, including Si wafers and carbon fibers, with the assistance of the photocatalytic ability and semiconductor characteristics of TiO2. A remarkable aspect ratio of up to 200 can be achieved. TEM analytical results suggest that the Pt NWs are single-crystalline with a preferred 〈111〉 growth direction. The precursor adopted and the heat treatment conditions are crucial for the yield of NWs. The photoelectrons supplied by TiO2 gives rise to the formation of nano-sized Pt nuclei from salt melt or solution. The subsequent growth of NWs is supported by the thermal electrons which also generated from TiO2 during the post thermal treatment. The interactions between the ions and the electrons in the Pt/TiO2 junction are discussed in this study.

Stannic oxide-titanium dioxide (SnO2–TiO2) coupled semiconductor photocatalyst loaded with polyaniline (PANI), a conducting polymer, possesses a high photocatalytic activity in oxidation of 1-octene to 1,2-epoxyoctane with aqueous hydrogen peroxide. The photocatalyst was prepared by impregnation ofSnO2and followed by attachment of PANI onto aTiO2powder to give sample PANI-SnO2–TiO2. The electrical conductivity of the system becomes high in the presence of PANI. Enhanced photocatalytic activity was observed in the case of PANI-SnO2–TiO2compared to PANI-TiO2,SnO2–TiO2, andTiO2. A higher photocatalytic activity in the oxidation of 1-octene on PANI-SnO2–TiO2thanSnO2–TiO2, PANI-TiO2, andTiO2can be considered as an evidence of enhanced charge separation of PANI-SnO2–TiO2photocatalyst as confirmed by photoluminescence spectroscopy. It suggests that photoinjected electrons are tunneled fromTiO2toSnO2and then to PANI in order to allow wider separation of excited carriers.

The photocatalytic splitting of water into hydrogen and oxygen using solar energy is a potentially clean and renewable source for hydrogen fuel. The first photocatalysts suitable for water splitting, or for activating hydrogen production from carbohydrate compounds made by plants from water and carbon dioxide, were developed several decades ago. But these catalysts operate with ultraviolet light, which accounts for only 4% of the incoming solar energy and thus renders the overall process impractical. For this reason, considerable efforts have been invested in developing photocatalysts capable of using the less energetic but more abundant visible light, which accounts for about 43% of the incoming solar energy. However, systems that are sufficiently stable and efficient for practical use have not yet been realized. Here we show that doping of indium-tantalum-oxide with nickel yields a series of photocatalysts, In(1-x)Ni(x)TaO(4) (x = 0-0.2), which induces direct splitting of water into stoichiometric amounts of oxygen and hydrogen under visible light irradiation with a quantum yield of about 0.66%. Our findings suggest that the use of solar energy for photocatalytic water splitting might provide a viable source for 'clean' hydrogen fuel, once the catalytic efficiency of the semiconductor system has been improved by increasing its surface area and suitable modifications of the surface sites.

A hybrid carbon fiber electrode (CFE) consisting of TiO2 semiconductor photocatalyst and Pt-Ru catalyst has been developed to boost the performance of direct methanol fuel cells (DMFC). These two catalyst nanoparticles are deposited on opposite sides of the carbon fiber paper such that methanol oxidation is carried out catalytically on Pt-Ru and photocatalytically on TiO2 under UV-light irradiation. Since both catalysts carry out methanol oxidation independently, we observe an additive effect in the current generation. The carbon support fibers provide a large network to collect the electrons from both of these catalytic processes and thus assist in efficient current generation. In addition, TiO2 improves the performance of the Pt-Ru catalyst in dark, indicating possible surface area improvement or diminished poisoning effects. The concept of incorporating a photocatalyst provides new ways to minimize precious metal content and enhance the performance of DMFCs. At low catalyst loadings (0.15 mg/cm2) at 295 K, a 25% enhancement in the peak power density is observed upon illumination with light.

Indicator inks, previously shown to be capable of rapidly assessing photocatalytic activity via a novel photo-reductive mechanism, were simply applied via an aerosol spray onto commercially available pieces of ActivTM self-cleaning glass. Ink layers could be applied with high evenness of spread, with as little deviation as 5% upon UV-visible spectroscopic assessment of 25 equally distributed positions over a 10cm×10cm glass cut. The inks were comprised of either a resazurin (Rz) or dichloroindophenol (DCIP) redox dye with a glycerol sacrificial electron donor in an aqueous hydroxyethyl cellulose (HEC) polymer media. The photo-reduction reaction under UVA light of a single spot was monitored by UV-vis spectroscopy and digital images attained from a flat-bed scanner in tandem for both inks. The photo-reduction of Rz ink underwent a two-step kinetic process, whereby the blue redox dye was initially reduced to a pink intermediate resorufin (Rf) and subsequently reduced to a bleached form of the dye. In contrast, a simple one-step kinetic process was observed for the reduction of the light blue redox dye DCIP to its bleached intermediates. Changes in red-green-blue colour extracted from digital images of the inks were inversely proportional to the changes seen at corresponding wavelengths via UV-visible absorption spectroscopy and wholly indicative of the reaction kinetics. The photocatalytic activity areas of cuts of ActivTM glass, 10cm×10cm in size, were assessed using both Rz and DCIP indicator inks evenly sprayed over the films; firstly using UVA lamp light to activate the underlying ActivTM film (1.75mWcm−2) and secondly under solar conditions (2.06±0.14mWcm−2). The photo-reduction reactions were monitored solely by flatbed digital scanning. Red-green-blue values of a generated 14×14 grid (196 positions) that covered the entire area of each film image were extracted using a custom-built program entitled RGB Extractor(C). A homogenous degradation over the 196 positions analysed for both Rz (Red colour deviation = 19% UVA, 8% Solar; Green colour deviation = 17% UVA, 12% Solar) and DCIP (Red colour deviation = 22% UVA, 16% Solar) inks was seen in both UVA and solar experiments, demonstrating the consistency of the selfcleaning titania layer on ActivTM. The method presented provides a good solution for the high-throughput photocatalytic screening of a number of homogenous photocatalytically active materials simultaneously or numerous positions on a single film; both useful in assessing the homogeneity of a film or determining the best combination of reaction components to produce the optimum performance photocatalytic film.

The photocatalytic splitting of water into hydrogen and oxygen using solar energy is a potentially clean and renewable source for hydrogen fuel. The first photocatalysts suitable for water splitting, or for activating hydrogen production from carbohydrate compounds made by plants from water and carbon dioxide, were developed several decades ago. But these catalysts operate with ultraviolet light, which accounts for only 4% of the incoming solar energy and thus renders the overall process impractical. For this reason, considerable efforts have been invested in developing photocatalysts capable of using the less energetic but more abundant visible light, which accounts for about 43% of the incoming solar energy. However, systems that are sufficiently stable and efficient for practical use have not yet been realized. Here we show that doping of indium-tantalum-oxide with nickel yields a series of photocatalysts, In(1-x)Ni(x)TaO(4) (x = 0-0.2), which induces direct splitting of water into stoichiometric amounts of oxygen and hydrogen under visible light irradiation with a quantum yield of about 0.66%. Our findings suggest that the use of solar energy for photocatalytic water splitting might provide a viable source for 'clean' hydrogen fuel, once the catalytic efficiency of the semiconductor system has been improved by increasing its surface area and suitable modifications of the surface sites.

Two-for-one approach to photoredox In photoredox catalysis, an excited chromophore typically activates a single reactant either by oxidizing or reducing it. Ghosh et al. used a semiconductor catalyst to activate two reactants at once by quenching both an excited electron and the residual positive hole (see the Perspective by Swift). As such, two different reactive carbon or halide fragments could be appended to separate sites on an aryl ring. The catalyst also tolerated strong nucleophiles such as cyanide and could be recovered easily and reused. Science , this issue p. 360 ; see also p. 320

A facile strategy based on the amidation reaction of anhydride and NH(2) group in carbon nitride polymer is developed to synthesize a new polymeric photocatalyst which responds to visible-light. The high photocatalytic activity may be due to the coupling anhydride groups promoting the separation of the photoinduced electrons and holes.

In situ attenuated total reflectance infrared (ATR-IR) spectroscopy has been used to determine the structure of adsorbed lactic acid (LA) compounds on the surfaces of titanium dioxide (TiO2) and cadmium sulfide (CdS) photocatalysts. LA was found to chelate onto the TiO2 in a b identate fashion, while in the CdS case, LA was adsorbed electrostatically as the lactate ion. These differing surface interactions are likely to determine the selectivity in the photo-products of LA.

Extra-fine crystallite of brookite TiO2, prepared by air oxidation of TiCl3 in aqueous HCl solution, exhibited marked photocatalytic activity for both dehydrogenation of propan-2-ol in aqueous solution and Ag metal deposition in silver sulfate solution.

Pure TiO2 nanoparticles (TiO2NPs) were produced via the sol–gel method and then coated with silver nanoparticles (AgNPs) to reduce their optical band gap. The concurrent synthesis and immobilization of AgNPs over TiO2NPs was achieved through the interaction of an open-air argon plasma jet with a solution of silver nitrate/stabilizer/TiO2NPs. The one-pot plasma synthesis and coating of AgNPs over TiO2NPs is a more straightforward and environmentally friendly method than others. The plasma-produced Ag/TiO2 nanocomposites were characterized and tested for their photocatalytic potential by degrading different concentrations of methyl blue (MB) in water. The dye concentration, oxidant dose, catalyst dose, and reaction time were also optimized for MB degradation. XRD results revealed the formation of pure AgNPs, pure TiO2NPs, and Ag/TiO2 nanocomposites with an average grain size of 12.36 nm, 18.09 nm, and 15.66 nm, respectively. The immobilization of AgNPs over TiO2NPs was also checked by producing SEM and TEM images. The band gap of AgNPs, TiO2NPs, and Ag/TiO2 nanoparticles was measured about 2.58 eV, 3.36 eV, and 2.86 eV, respectively. The ultraviolet (UV) results of the nanocomposites were supportive of the degradation of synthetic dyes in the visible light spectrum. The AgNPs in the composite not only lowered the band gap but also obstructed the electron–hole recombinations. The Ag/TiO2 composite catalyst showed 90.9% degradation efficiency with a 5 ppm dye concentration after 120 min of light exposure.

Wastewater produced by the textile industry contains various dyes and organic compounds that directly or indirectly affect surface water or groundwater pollution. Visible-light-driven semiconductor photocatalysis is the leading pathway for the degradation of environmental pollutants. Herein we report the bottom-up hydrothermal growth of 2D tin disulfide nanostructures (SnS2 NSs) for the efficient photodegradation of organic pollutants such as Rhodamine B (Rh.B) and Methyl Violet (M.V) in an aqueous medium under visible light (λ > 400 nm) irradiation. The as-synthesized SnS2 NSs were characterized by various structural, morphological, and optical techniques such as XRD, RAMAN, TEM, UV–Vis, Brunauer–Emmett–Teller, etc. Furthermore, the low bandgap (∼1.6 eV), the high surface area (56 m2/g), and the anionic nature of SnS2 NSs attribute to it as an efficient photocatalyst for photocatalytic applications. The photocatalytic properties of SnS2 NSs showed good degradation efficiency of 94 and 99.6% for Rh. B and M.V, respectively, in 25 min. The kinetic rate constant of these dyes was estimated by using the Langmuir–Hinshelwood model. Here we also performed the recyclability test of the photocatalyst and discussed the plausible mechanism for the photocatalytic degradation of organic pollutants. The XPS spectra of SnS2 NSs were studied before and after the photodegradation of Rh.B and M.V, indicating the high stability of the photocatalyst. Moreover, in vitro cytotoxicity was also evaluated against human cervical cancer cell lines (HeLa cells) with different concentrations (0–1,000 μg/ml) of as-synthesized SnS2 NSs. This intended work provides a possible treatment for the degradation of organic pollutants under visible light to balance the aquatic ecosystems.

Ag3PO4/g-C3N4 heterojunctions, with different g-C3N4 dosages, were synthesized using an in situ deposition method, and the photocatalytic performance of g-C3N4/Ag3PO4 heterojunctions was studied under simulated sunlight conditions. The results revealed that Ag3PO4/g-C3N4 exhibited excellent photocatalytic degradation activity for rhodamine B (Rh B) and phenol under the same light conditions. When the dosage of g-C3N4 was 30%, the degradation rate of Rh B at 9 min and phenol at 30 min was found to be 99.4% and 97.3%, respectively. After five cycles of the degradation experiment for Rh B, g-C3N4/Ag3PO4 still demonstrated stable photodegradation characteristics. The significant improvement in the photocatalytic activity and stability of g-C3N4/Ag3PO4 was attributed to the rapid charge separation between g-C3N4 and Ag3PO4 during the Z-scheme charge transfer and recombination process.

Methane is one of the promising alternatives of petroleum, which should be used for not only a fuel but also a resource for hydrogen and more useful chemicals as with the petroleum. However, the selective methane conversion to them is still difficult in contrast to the combustion. Three types of photocatalytic reactions for methane conversion, i.e., the photocatalytic non-oxidative coupling of methane (2CH[4] → C[2]H[6] + H[2]), the photocatalytic dry reforming of methane (CH[4] + CO[2] → 2CO + 2H[2]) and the photocatalytic steam reforming of methane (CH[4] + 2H[2]O → 4H[2] + CO[2]), can take place around room temperature or at a mild condition such as 473 K using photoenergy and semiconductor photocatalyst. In the present short review, the details of each photocatalytic reaction and the design concept of the semiconductor photocatalysts for each photocatalytic methane conversion were summarized and discussed.

Two-dimensional thin Bi2WO6 nanoplates have been fabricated using a cetyltrimethylammonium bromide (CTAB)-assisted hydrothermal method. We investigated the proposed formation mechanism based on the crystalline structures of the thin Bi2WO6 nanoplates. The high adsorption ability and excellent visible-light driven photocatalytic activities of the Bi2WO6 nanoplates were illustrated, in view of exposed (001) facets of nanoplates possessing faster separation of photo-generated charge carriers and increased catalytically active sites. Such a cost-effective way to obtain Bi2WO6 nanoplates offers new possibilities for the design of adsorptive semiconductor photocatalysts with strengthened photocatalytic activities.

The mechanism of PdCrOx multi-component cocatalyst formation on SrTiO3 was investigated using transmission electron microscopy, X-ray absorption fine structure spectroscopy and X-ray photoelectron spectroscopy. The PdCrOx/SrTiO3 samples were synthesized by a photodeposition method under UV light irradiation (λ &gt, 300 nm) for various time periods (0–5 h). The fine structure and valence state of the Pd species of PdCrOx nanoparticles were varied from Pd oxide to a mixture of metallic Pd and oxidized Pd species with an increase in the irradiation time. The overall water-splitting activity of PdCrOx was strongly dependent on the photoirradiation time during deposition. Although longer photoirradiation time during preparation did not influence the H2 evolution activity of PdCrOx/SrTiO3 from aqueous methanol solution, it was effective in suppressing the O2 photoreduction activity, which is one of the backward reactions during overall water splitting.

Highly hierarchical hollow bismuth tungstate (Bi2WO6) microspheres self-assembled by thin nanoplates have been fabricated via a facile template-free solvothermal route. The possible growth pattern and formation mechanism of hierarchical hollow Bi2WO6 microspheres was investigated. The excellent visible-light-driven photocatalytic performance on rhodamine B (RhB) degradation was displayed by hierarchical hollow Bi2WO6 microspheres. Such well-organized hierarchical hollow Bi2WO6 microspheres show potential application in water treatment fields by full use of solar energy.

Background: The present scenario of rapid industrial and population growth has become a serious threat to environmental and energy concerns. Extremely noxious pollutants like dyes, heavy metal ions, phenols, antibiotics and pesticides in water are the reason behind deprived water quality leading to inadequate access to clean water. Photocatalysis is a prominent strategy for environmental remediation as photocatalytic materials not only convert solar energy into usable energy expedient but also shows potential application in pollutant mitigation. An effectual photocatalytic system must possess wide visible absorption range, high physio-chemical firmness, and effective space-charge separation along with strong redox ability. Polymeric graphitic carbon nitride a metal-free semiconductor photocatalyst has outshined as a robust photocatalyst for various photocatalytic applications. Methods: Hybridizing polymeric g-C3N4 with other semiconductor photocatalysts has not only conquer the limitations related to pristine g-C3N4 but also displayed improved photoactivity. Different photocatalytic systems involving g-C3N4 coupled metal-oxides, metal-free systems and complex heterojunction systems are reviewed. Moreover, an all-embracing study based on g-C3N4 based nanocatalysts is explored via heterojunction formation taking g-C3N4 as one component. Results: Photocatalytic experiments involving photodegradation of pollutants, revealed the significance of metal-free g-C3N4 in the heterojunction system which remarkably boost the photoactivity through effective separation and migration of photocarriers. Moreover, from recyclability experiments, exceptional photostability of g-C3N4 based photocatalysts was observed. Photocatalytic pollutant degradation is a complex phenomenon which requires significant experimental techniques to support the mechanism. With the help of photoelectrochemical analysis, the mechanisms behind photodegradation can be evaluated and explored. Conclusion: Metal-free polymeric g-C3N4 is a potential semiconductor photocatalyst which can be optimally utilized for wastewater treatment. Coupling g-C3N4 with another semiconductor material with an appropriate band edge can effectively enhance the photocatalytic efficacy. Herein, g-C3N4 derived metal-oxide, metal-free and complex heterojunction systems are explored and their photocatalytic efficiency is evaluated for pollutant degradation. However, more effective research efforts are needed for large-scale applications of g-C3N4 based photocatalysts.

Selective synthesis of organic chemicals such as oxidation of toluene to benzaldehyde using sunlight is necessary for its sustainable and environment-friendly applications. The photocatalytic reaction using semiconductor photocatalysts is a promising approach for sunlight-induced organic synthesis due to its significant advantages of operation under mild conditions, stability, and recyclicity. TiO2 is one of the most widely studied photocatalysts; however, the low selectivity for partial oxidation due to the complete decomposition to CO2 and lack of utilization of visible-light hampers its practical application. Here, we successfully demonstrated selective oxidation of toluene to benzaldehyde using a Pd-loaded BiVO4 photocatalyst under visible light irradiation. Furthermore, we confirmed that the reaction proceeds even under light irradiation up to 520 nm; this is the first report using blue-to-green light-responsive semiconductor photocatalyst for converting toluene to benzaldehyde. Achieving efficient organic synthesis under visible light using semiconductor photocatalyst is an important step toward solar-to-chemical conversion.

Rh-doped SrTiO3 (Rh-STO) is a visible-light-responsive oxide semiconductor photocatalyst with applications to water splitting. In this work, the onset potentials of the Rh-STO electrodes were shifted in a wide range from 0 to 1.2 V vs. RHE via changing the amount of Rh dopants, or adjusting the ratio of Ti3+/Rh4+,3+ cations through a vacuum-heating treatment. Namely, the photocathodic and photoanodic behavior of this material was successfully altered. The Rh4+,3+ cations that composing the acceptor energy levels of Rh-STO were characterized with UV–Vis diffuse reflectance and X-ray photoelectron spectroscopies. Visible-light-driven low-biased photoelectrochemical water splitting was achieved by connecting the as-prepared Rh-STO photoanode and photocathode in series. This work provides a new strategy of accomplishing overall water splitting using only one kind of semiconductor photocatalyst.

A wide range of processes have been adopted for environmental remediation; among them, photocatalysis appeared as an appealing strategy for degradation of organic pollutants. Heterogeneous photocatalysis efficiently dissociates the charge carriers and helps in reducing the rapid recombination rate of charge carriers resulting in enhanced photocatalytic degradation. A semiconductor photocatalyst graphitic carbon nitride (g-C3N4), when doped with metals or non-metals, showed increased degradation abilities. Hence, a ternary photocatalyst was synthesized by thermal condensation of urea coupled with ferric tungstate (FeWO4) and doped with a noble metal (Ag) resulting in visible light susceptive semiconductor photocatalyst Ag/FeWO4/g-C3N4. The characterization of the fabricated composite was done by Fourier transform infrared, scanning electron microscopy energy-dispersive X-ray, and X-ray diffraction. The Ag/FWO/GCN was used to degrade the rhodamine B (RhB) dye. Under sunlight, Ag/FeWO4/g-C3N4 showed enhanced photocatalytic degradation of rhodamine B dye, which was ascribed to the change in bandgap and reduced charge recombination. The parameters used for the optimization of the photocatalyst were pH, catalyst dose, oxidant dose, and irradiation time. The composite (Ag/FeWO4/g-C3N4) showed ~ 98% degradation of RhB dye under optimized conditions (i.e., pH = 8, catalyst dose = 50 mg/100 ml, oxidant dose = 9 mM, irradiation time = 120 min and RhB conc. 50 ppm).