Search

TiO2 was modified with sulfate and phosphate (denoted as S/TiO2 and P/TiO2) through a simple sulfuric or phosphoric acid treatment. A strong coordination bond forms between sulfate or phosphate and Ti4+ of TiO2. Eosin Y (EY)-sensitized S/TiO2 and P/TiO2 (Pt as a co-catalyst and triethanolamine as a sacrificial electron donor) exhibit enhanced photocatalytic activity for hydrogen evolution under visible light illumination (λ ＞ 420 nm) compared to that of EY-sensitized TiO2. The conduction band (CB) edges of S/TiO2 and P/TiO2 shift toward the negative, and the hydrogen bond interaction between the reduced radical EYṖ–H and S/TiO2 or P/TiO2 is enhanced due to the inducing effect of the bound sulfate and phosphate. Thus, the photocatalytic hydrogen evolution is promoted. The effects of the concentration of the sulfuric or phosphoric acid as well as concentration of EY on the sensitization hydrogen evolution were investigated. The possible mechanism was discussed. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we report the obtention of a series of rare earth doped composite Pt/RE/TiO2-CdS (RE=La3+, Eu3+, Er3+, Gd3+) and TiO2-CdS photocatalysts prepared by a simple mechanical mixed method. The photocatalysts properties were studied by means of ultraviolet-visible spectroscopy, photoluminiscence spectra, X-ray diffraction, transmission electron microscopy, specific surface areas and the electrochemistry method. Photocatalytic hydrogen evolution using Na2S/Na2SO3 as electron donor was investigated under visible-light (λ≥420nm) irradiation. The rare earth doping enhances the activities of Pt/RE/TiO2-CdS samples (with 1.0wt% deposited Pt). Under optimum conditions, the activities of La3+, Eu3+, Er3+, Gd3+ doped composite Pt/RE/TiO2-CdS increase by 62.0%, 40.4%, 34.7% and 30.0% respectively, when compared to that of Pt/TiO2-CdS, due to the prevention of electron–hole recombination and the flat-band potential of the conduction of TiO2 shifting negatively by the doping. [Copyright &y& Elsevier]

CdZnS and Ru doped Ru(m)/CdZnS photocatalysts were prepared by a simple hydrothermal method, and characterized by X-ray diffraction, UV-Vis absorption spectroscopy and electrochemistry techniques. Their photoactivities were evaluated by hydrogen evolution from aqueous solution containing NaS and NaSO as a hole scavenger under visible light (λ ≥ 420 nm) irradiation. Ru doping enhances the photocatalytic activity markedly. It was found that 0.10 mol% Ru doped CdZnS photocatalyst showed the highest activity. The reason for the positive effects of Ru was discussed. [ABSTRACT FROM AUTHOR]

Abstract: Bi3+ doped Cd0.5Zn0.5S photocatalysts were prepared by a simple hydrothermal method, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscope (XPS), energy dispersive X-ray spectroscopy (EDX), BET and UV-Vis absorption spectroscope techniques. When Bi3+ doping content is lower, the doping ions lie at the surface lattice sites, whereas when the doping content is higher, the ions also enter the bulk lattice sites. Their photoactivities were evaluated by hydrogen evolution from aqueous solution containing Na2S and Na2SO3 as a hole scavenger under visible light (λ ≥ 420 nm) irradiation. Bi3+ doping enhances markedly photocatalytic activity. When Bi3+ doping content is 0.10 mole %, the photocatalyst exhibits the highest activity, and the average apparent quantum yield amounts to 9.71% during 30 h irradiation. The possible mechanism was discussed. [Copyright &y& Elsevier]

Using glycerol as electron donor, photocatalytic hydrogen generation over Pt/TiO2 was investigated. The results show that glycerol can not only improve the efficiency of photocatalytic hydrogen generation but can also be decomposed effectively. The factors which affect photocatalytic hydrogen generation, such as irradiation time, initial concentration of the glycerol solution, pH-value of the suspensions and the coexisting substances were studied. The final oxidation products of glycerol were H2O and CO2. Glyceraldhyde, glycoladehyde, glycolic acid and formaldehyde were identified as the intermediates. A possible reaction mechanism was discussed. [ABSTRACT FROM AUTHOR]

TiO2 photocatalysts doped with Be2+ were prepared by impregnation and coprecipitation method. The samples were characterized by XRD, XPS and IR. Their activities were evaluated by photocatalytic hydrogen production. It is found that Be2+ can enter into the interstitial site of TiO2 lattice, and the photocatalytic activities depend on doping method. When the doping ions were in the shallow surface, the doping was beneficial; while in the deep bulk, the doping was detrimental. On the optimum conditions, the photocatalytic activity of the doped TiO2 increased by 75% compared to pure TiO2. [Copyright &y& Elsevier]

Abstract: NiS was loaded on ZnS1−x−0.5y O x (OH) y –ZnO photocatalyst by two methods (depositing NiS on the photocatalyst via impregnation with a NiS sol and via a precipitation reaction). The activity of the NiS-modified photocatalyst for hydrogen evolution from pure water and seawater was investigated using mixed electron donors (sulfide and sulfite). The activity (in pure water-electron donor solution) is dependant of the modification method and loading content of NiS. When Na2S·9H2O and Na2SO3 are added into seawater, a mixture precipitate (Mg(OH)2 and CaSO3) produces. The precipitate is detrimental to the photocatalytic hydrogen evolution over the unmodified ZnS1−x−0.5y O x (OH) y –ZnO. However, for the NiS-modified photocatalyst, the detrimental effect decreases notably. Interestingly, the activity of the modified photocatalyst in seawater-electron donor solution (with the precipitate) is higher than that in the pure water-electron-donor solution (without the precipitate). The possible mechanism was discussed. [Copyright &y& Elsevier]

Abstract: Stability issue of dye limits greatly applications of sensitization systems. In the present work, TiO2 was modified with a lacunary Keggin-type polyoxometalate SiW11O39 8− (SiW11). SiW11 is bound at TiO2 by a chemical interaction and its modification promotes TiO2 crystallization as well as growth of the particles. The as-prepared SiW11/TiO2 was used to construct a stable and efficient system for visible-light H2 generation using Eosin Y (EY) as a photosensitizer and Pt as a co-catalyst. SiW11 plays a very important role in enhancement of the sensitization activity and stability of SiW11/TiO2. SiW11 as an excellent electron relay greatly facilitates the electron transfer from the reduced dye species EY − to conduction band (CB) of TiO2 and suppresses the decomposition of EY −. Thus, a stable dye-sensitized hydrogen generation system is achieved. The factors which influenced the photocatalytic hydrogen evolution such as concentration of SiW11, concentration of EY, and Pt loading content were investigated. Under the optimal conditions, an average apparent quantum yield of 11.4% was obtained during 20 h irradiation (λ > 420 nm). The possible mechanism was discussed. [Copyright &y& Elsevier]

Abstract: Zr-doped TiO2 nanotube arrays (Zr-TiO2-NT) and TiO2 nanotube arrays (TiO2-NT) were prepared via anodic oxidation of titanium foils in ethylene glycol solution and modified by heat treatment in the presence of urea pyrolysis products at 400°C. Zr doping changes the morphology of Zr-TiO2-NT and its conduction band edge shifts negatively compared with that of TiO2-NT. For the modification of Zr-TiO2-NT in the presence of urea pyrolysis products, Zr doping can not only enhance the polymerization degree of the surface-modified carbon nitride polymers but also promote the N doping. The modified TiO2-NT and Zr-TiO2-NT films exhibit significant photocurrent responses upon visible light irradiation. Zr doping improves markedly the visible-light photoelectrochemical H2 production of the modified Zr-TiO2-NT. [Copyright &y& Elsevier]

Abstract: Using ethanolamine (EA), diethanolamine (di-EA) and triethanolamine (tri-EA) as electron donors, the photocatalytic hydrogen evolution and decomposition of the electron donors (pollutants) over Pt/ZnIn2S4 have been investigated. The Pt was deposited on ZnIn2S4 by in situ photoreduction. The three ethanolamines improve notably photocatalytic hydrogen generation with their simultaneous degradation, and their activity order for hydrogen evolution is tri-EA≫di-EA>EA. The adsorption of these donors on ZnIn2S4 was monitored by in situ attenuated total reflection infrared spectroscopy (ATRIR). The order of their adsorption intensity is EA>di-EA≫tri-EA. The activity order depends on their molecular structure and adsorption performance. The effect of concentration of the pollutants on the hydrogen generation rate is consistent with a Langmuir–Hinshelwood kinetic model. The weak basic condition is favorable for the photocatalytic hydrogen generation. A possible reaction mechanism was discussed. [Copyright &y& Elsevier]

Abstract: It is important to construct a stable and efficient dye sensitization system for visible-light photocatalytic hydrogen evolution. Eosin Y (EY)-sensitized α-[AlSiW11(H2O)O39]5− (AlSiW11) (an Al3+ substituted Keggin polyoxometalate (POM)) for the hydrogen evolution under visible light irradiation (λ > 420 nm) has been carried out in the presence of triethanolamine as electron donor and Pt as co-catalyst. EY can coordinate with AlSiW11. The coordination association between AlSiW11 and EY is beneficial to the charge transfer from EY to AlSiW11 and to stability of EY. The system displays efficient and stable photocatalytic hydrogen evolution. The average apparent quantum efficiency and turnover number of EY during 20 h irradiation (λ > 420 nm) are 10.3% and 473, respectively. The highest quantum efficiency amounts to 28.0% under 520 nm monochromatic light irradiation. The present study highlights linking between dye and POM molecule as a way to develop new visible-light stable photocatalyst or system. [Copyright &y& Elsevier]

Abstract: Photocatalytic hydrogen production was investigated over ZnS1−x−0.5y O x (OH) y –ZnO using sulfide ion (Na2S–Na2SO3) as an electron donor from NaCl saltwater. NaCl can affect markedly the activity for photocatalytic hydrogen production, depending on NaCl concentration. When NaCl concentration is lower, the activity is lower than that in pure water, whereas when NaCl concentration is higher, the activity is higher than that in pure water. NaCl decreases not only the surface charge of ZnS1−x−0.5y O x (OH) y –ZnO but also the surface hydration. When ZnS1−x−0.5y O x (OH) y –ZnO was impregnated with the electron donor (Na2S–Na2SO3), ZnO was transformed partly into ZnS. The impregnated ZnS1−x−0.5y O x (OH) y –ZnO exhibits higher activity than the non-impregnated one. The possible mechanisms were discussed. [Copyright &y& Elsevier]

Abstract: Surface property of Cd0.5Zn0.5S in basic aqueous solution was characterized by X-ray photoelectron spectroscope (XPS). The surface S species at Cd0.5Zn0.5S under basic condition is substituted by O species. The surface adsorption performance of glucose and NaCl was characterized by adsorption experiment and electrophoretic analysis. Glucose is adsorbed on Cd0.5Zn0.5S via two modes. Na+ can be also adsorbed on Cd0.5Zn0.5S. The effect of electrolyte NaCl on photocatalytic hydrogen evolution over Pt/Cd0.5Zn0.5S using glucose as an electron donor has been investigated under visible light irradiation. NaCl can promote markedly the photocatalytic hydrogen evolution, which is very important to practical application. The photocatalytic activity for hydrogen evolution from 3.0 mol L−1 NaCl saltwater increases by 77% compared to that from pure water. A possible mechanism was discussed. [Copyright &y& Elsevier]

Abstract: A nitrogen-doped TiO2 (N-TiO2) photocatalyst was prepared by calcination of the hydrolysis precipitate of Ti(SO4)2 with aqueous ammonia. The prepared N-TiO2 was treated with NH4F (F-N-TiO2) by an impregnation-calcination method. The photocatalyst (F-N-TiO2) was characterized by X-ray diffraction (XRD), Fourier Transform Infrared (FT-IR), UV–vis diffusive reflectance spectroscopy (DRS), BET and X-ray photoelectron spectroscopy (XPS). With blue light-emitting diode (LED) as the light source, its photocatalytic activity for the degradation of formaldehyde was investigated. NH4F treatment enhances markedly photocatalytic activity of N-TiO2. The treatment increases the visible absorption of N-TiO2, decreases its specific surface area and influences the concentration of oxygen vacancies in N-TiO2. Photocatalytic activity of F-N-TiO2 depends on the visible absorption, the specific surface area, and the concentration of oxygen vacancies. The preparation conditions, such as the calcination temperature and the initial molar ratio of NH4F to N-TiO2, have a significant influence on the photocatalytic activity. The doping mechanism of NH4F was investigated. [ABSTRACT FROM AUTHOR]

Abstract: ZnS coated ZnIn2S4 (ZnS–ZnIn2S4) photocatalysts were prepared in methanol by a facile solvothermal process. The photocatalysts were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), UV–Vis diffusive reflectance spectroscopy (DRS), BET, and electrochemistry measurements. ZnS–ZnIn2S4 photocatalysts have hexagonal crystal phase and complex morphology such as micro-spheres, micro-tubes and micro-ribbons. Using glucose as an electron donor, photocatalytic hydrogen generation over Pt/ZnS–ZnIn2S4 was investigated. The results show that photoactivity of hydrogen generation over Pt/ZnS–ZnIn2S4 was improved notably with simultaneous degradation of glucose. The factors which affect photocatalytic hydrogen generation, such as composition of ZnS-ZnIn2S4, initial concentration of glucose and concentration of NaOH, were investigated. The prepared ZnS–ZnIn2S4 photocatalysts exhibit better activity for hydrogen generation than pure ZnIn2S4, which may be attributed to enhancement of the adsorption of glucose by ZnS on the ZnIn2S4 surface. The effect of glucose concentration on the hydrogen generation rate is consistent with a Langmuir model. The basic condition is favorable for the photocatalytic hydrogen generation. A large number of ·OH radicals generated in ZnS–ZnIn2S4 system, have been tested by a TA-FL (terephthalic acid-fluorescence) method. A possible mechanism was discussed. [Copyright &y& Elsevier]

Abstract: An efficient visible-light active photocatalyst of multilayer-Eosin Y-sensitized TiO2 is prepared through linkage of Fe3+ between not only TiO2 and Eosin Y but also different Eosin Y molecules to form three-dimensional polymeric dye structure. The multilayer-dye-sensitized photocatalyst is found to have high light harvesting efficiency and photocatalytic activity for hydrogen evolution under visible light irradiation (λ >420nm). On the optimum conditions (1:1 initial molar ratio of Eosin Y to Fe(NO3)3, initial 10×10−3 M Eosin Y, and 1.0 wt% Pt deposited by in situ photoreduction), its maximal apparent quantum yield for hydrogen evolution is 19.1% from aqueous triethanolamine solution (TEOA aq). The present study highlights linking between dye molecules via metal ions as a general way to develop efficient visible-light photocatalyst. [Copyright &y& Elsevier]

Abstract: A composite visible light photocatalyst was prepared through co-precipitation of Zn(NO3)2 in the mixed solution of aqueous Na2S and NaOH, and calcination in N2 atmosphere. The photocatalyst was characterized by thermogravimetric and differential thermal analysis (TG–DTA), X-ray diffraction (XRD), UV–vis diffusive reflectance spectroscopy (DRS), BET and electrochemistry measurements. Its activity was evaluated by hydrogen production from an aqueous solution containing Na2S and Na2SO3 as hole scavengers under visible light (λ ≥420nm) irradiation. The photocatalyst is a mixture of basic zincoxysulfide (ZnS1−x−0.5y O x (OH) y ) solid solution and ZnO or only the solid solution. ZnS1−x−0.5y O x (OH) y , which was visible light active, was a solid solution of ZnS with dissolved oxygen and hydroxide groups. Hydroxide groups are very important in the formation and stabilization of the solid solution. The precipitation and calcination temperatures as well as the precursor composition of ZnS1−x−0.5y O x (OH) y have great influence on the photocatalytic activity. With 1:1 calculated molar ratio of ZnS to ZnO (or Zn(OH)2), ZnS1−x−0.5y O x (OH) y photocatalyst prepared via co-precipitation at 373K and calcination at 673K under N2 atmosphere exhibits the highest activity. Its apparent quantum yield without noble metal cocatalyst is ca. 3.0% under visible light irradiation. [Copyright &y& Elsevier]

Abstract: A nitrogen-doped TiO2 (N-TiO2) photocatalyst was prepared by the calcination of the hydrolysis product of Ti(SO4)2 with aqueous ammonia. Pt was loaded on N-TiO2 by photodeposition method. A dye-sensitization photocatalyst was prepared by impregnation method with Eosin Y and the platinized N-TiO2. The prepared samples were characterized by XRD, UV–vis diffuse reflectance spectra (DRS), BET and FT-IR. The visible light activity of the sensitization photocatalysts was evaluated by photocatalytic hydrogen evolution (λ >420nm) in the presence of electron donor triethanolamine (TEOA). The N-TiO2 has smaller crystalline size and larger specific surface area to enhance the adsorption amount of Eosin Y than TiO2 prepared by NaOH. Surface oxygen defects produced by nitrogen doping would improve the adsorption of Eosin Y and excited electron to transfer to the conduction band of N-TiO2. Therefore the visible light activity of the sensitized nitrogen-doped platinized TiO2 is much higher than that of the sensitized platinized TiO2. The sensitized nitrogen-doped platinized TiO2 calcined at 300°C has the highest visible light activity among the catalysts calcined at various temperatures, whose activity is increased by a factor of 3 compared to that of the sensitized platinized TiO2 calcined at the same temperature. [Copyright &y& Elsevier]

Constructing heterojunctions to separate photogenerated carriers is an effective strategy for improving the efficiency of photocatalytic reactions. A J-type heterojunction is a recently reported efficient anisotropic heterojunction. Herein, taking anisotropic ZnIn 2 S 4 (ZIS) nanosheets as an example of a type-II heterojunction, we report for the first time the concept of open and closed structures (O and C structure) of J-type heterojunctions. A simple ammonia-post-treatment method was employed to prepare the O- and C-structured J-type ZnIn 2 S 4 /In(OH) 3 (ZIS/IOH) heterojunctions. The O-structured J-type ZIS/IOH (OJ-ZIS/IOH) heterojunction exhibits a high hydrogen production activity, reaching 400 μmol·h -1 , 2.67 times higher than that of pristine ZIS. However, the activity of the C-structured heterojunction (CJ-ZIS/IOH) is close to that of pristine ZIS. The findings emphasize the importance of the cooperation of photogenerated carrier separation and transport in J-type heterojunctions, providing insights into developing efficient heterojunction photocatalysts.

Graphitic carbon nitride (g-C 3 N 4 ), as an attractive metal-free polymer photocatalyst, has attracted extensive attention in energy and environmental fields in recent years. The photoactivity of bulk g-C 3 N 4 is moderate on account of solid-phase thermal-condensation synthesis. This leads to inadequate light absorption, limited surface area, and easy recombination of charge carriers. The composition and nanostructure of g-C 3 N 4 have been studied extensively. Molten-salt modulation is fascinating because of its "green" credentials and the properties of liquid-phase reaction systems. The review focuses mainly on molten-salt modulation of the composition and structure of g-C 3 N 4 based-photocatalysts. We focus on elemental doping, molecular doping, and defect engineering, as well as control of the crystal structure, multi-dimensional structure, hom/heterostructures for photocatalytic applications. This review provides new insights to develop g-C 3 N 4 -based photocatalysts with control of composition and structure by facile molten-salt modulation in energy-conversion and environmental fields.

Crystalline carbon dots (CCDs) embedded in carbon nitride (CN) nanofragments (CCDs-CN) have been developed through facile molten salt treatment. Molten salt treatment not only reconstructs CN layered sheets to form nanofragments, but also promotes the crystallization of CDs-CN. The π-conjugated electric field between CCDs and CN accelerates charge carrier separation for efficient photocatalytic H 2 evolution.

Condensed π-conjugation C-PAN/MS-CN nanotubes were obtained via a facile polyacrylonitrile (PAN)-confined molten salt (MS) thermal condensation of melamine. Carbonized PAN (C-PAN) nanosheets with a conjugate network structure in the molten salt system acted as partition plates confining the thermal condensation of melamine, which promoted the formation of condensed π-conjugation carbon nitride (CN) for the effective charge carrier separation and photocatalytic H 2 evolution.

Polar metals, commonly defined by the coexistence of polar structure and metallicity, are thought to be scarce because free carriers eliminate internal dipoles that may arise owing to asymmetric charge distributions. By using first-principle electronic structure calculations, we explored the possibility of producing metallic states in the polar/nonpolar KNbO 3 /BaTiO 3 superlattice (SL) composed of two prototypical ferroelectric materials: BaTiO 3 (BTO) and KNbO 3 (KNO). Two types of polar/nonpolar interfaces, p-type (KO) - /(TiO 2 ) 0 and n-type (NbO 2 ) + /(BaO) 0 , which can be constituted into two symmetric NbO 2 /BaO-NbO 2 /BaO (NN-type) and KO/TiO 2 -KO/TiO 2 (PP-type) SL, as well as one asymmetric KO/TiO 2 -NbO 2 /BaO (PN-type) SL. The spatial distribution of ferroelectric distortions and their conductive properties are found to be extraordinarily sensitive to the interfacial configurations. An insulator-to-metal transition is found in each unit cell of the symmetric interfacial SL models: one exhibiting quasi-two-dimensional n-type conductivity for NN-type SL, while the other being quasi-two-dimensional p-type conductivity for PP-type SL. The anisotropic coexistence of in-plane orientation of free carriers and out-of-plane orientation of ferroelectric polarization in KNO/BTO SL indicates that in-plane free carriers can not eliminate the out-of-plane dipoles. Our results provide a road map to create two-dimensional polar metals in insulating perovskite oxide SL, which is expected to promote applications of new quantum devices., Competing Interests: The authors declare no competing financial interest., (This journal is © The Royal Society of Chemistry.)