02501nas a2200217 4500008004100000022001400041245013500055210006900190260005700259300001400316490000700330520168200337100001502019700001502034700002002049700002102069700002702090700001802117700001802135856013002153 2011 eng d a0022-246100aRole of doping-induced photochemical and microstructural properties in the photocatalytic activity of InVO4 for splitting of water0 aRole of dopinginduced photochemical and microstructural properti a233 SPRING ST, NEW YORK, NY 10013 USAbSPRINGERcAUG a5466-54760 v463 a

We report in this paper on microstructural, optical and photocatalytic properties of single-phase indium orthovanadates, as a function of doping at lattice sites. The UV-visible spectra of these samples exhibited intense UV-region bands at 250 and 350 nm, besides broad absorption band in visible region (350-700 nm). The wavelength at absorption edge and the intensity of visible absorption showed considerable increase on doping of an impurity, particularly at V or O lattice sites. Also, the samples gave rise to blue-green photoluminescence emission, with overriding bands at ca. 420, 450, 460 and 485 nm, on excitation at 240-420 nm wavelengths. The intensity of these fluorescence bands varied with excitation wavelength and impurity content of a sample. In deviation with several earlier studies, only oxygen and no hydrogen were produced during photocatalytic splitting of water, in the experiments conducted under visible light (> 395 nm) and at a pH of similar to 6.5. The O-2 yield depended on the dispersed metal co-catalyst, impurity content and the addition of methanol as sacrificial reagent. On the other hand, small quantities of hydrogen and no oxygen were evolved on UV-irradiation of pure water using metal/InVO4. These results are ascribed to flat band potentials and the doping-induced inter-band donor and acceptor charge trapping states of InVO4, the presence of which is revealed by XRD, luminescence and XPS studies. Our study also confirms that the onset of absorption edge may not necessarily correspond to band-to-band energy gap of a semiconducting material. This accounts for some anomalous band gap energies reported earlier for InVO4.

1 aRakesh, K.1 aKhaire, S.1 aBhange, Deu, S.1 aDhanasekaran, P.1 aDeshpande, Suvarna, S.1 aAwate, S., V.1 aGupta, N., M. uhttps://library.ncl.res.in/content/role-doping-induced-photochemical-and-microstructural-properties-photocatalytic-activity-002739nas a2200193 4500008004100000022001400041245018300055210006900238260011000307300001600417490000700433520188100440100001802321700002702339700001502366700002102381700001802402856012502420 2011 eng d a1463-907600aRole of micro-structure and interfacial properties in the higher photocatalytic activity of TiO2-supported nanogold for methanol-assisted visible-light-induced splitting of water0 aRole of microstructure and interfacial properties in the higher  aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcMAY a11329-113390 v133 a

This paper deals with the textural, microstructural and interfacial properties of Au/TiO2 nanocomposites, in relation to their photocatalytic activity for splitting of water. TiO2 samples of two different morphologies were employed for dispersing different cocatalysts, such as: Au, Pt, Ag or Cu, for the sake of comparison. The samples were characterized using powder XRD, XPS, UV-visible, thermoluminescence, SEM, HRTEM and SAED techniques. Compared to other metal/TiO2 photocatalysts, Au/TiO2 with an optimum gold loading of 1 wt% was found to exhibit considerably higher activity for visible light induced production of H-2 from splitting water in the presence of methanol. Further, the sol-gel prepared TiO2 (s.TiO2), having spherical grains of 10-15 nm size, displayed better photoactivity than a Degussa P25 catalyst. The electron microscopy investigations on s.TiO2 revealed significant heterogeneity in grain morphology of individual TiO2 particles, exposure of the lattice planes, metal dispersion, and the interfacial metal/TiO2 contacts. The gold particles were found to be in a better dispersed state. O-2 TPD experiments revealed that the gold nanoparticles and Au/TiO2 interfaces may serve as distinct binding sites for adsorbate molecules. At the same time, our thermoluminescence measurements provide an insight into Au-induced new defect states that may facilitate the semiconductor-to-metal charge transfer transition. In conclusion, the superior photocatalytic activity of Au/TiO2 may relate to the grain morphology of TiO2, dispersion of gold particles, and the peculiar architecture of metal/oxide heterojunctions; giving rise in turn to augmented adsorption of reactant molecules and their interaction with the photo-generated e(-)/h(+) pair. The role played by methanol as a sacrificial reagent in photocatalytic splitting of water is discussed.

1 aAwate, S., V.1 aDeshpande, Suvarna, S.1 aRakesh, K.1 aDhanasekaran, P.1 aGupta, N., M. uhttps://library.ncl.res.in/content/role-micro-structure-and-interfacial-properties-higher-photocatalytic-activity-tio2-002032nas a2200217 4500008004100000022001400041245013700055210006900192260010600261300001400367490000700381520115400388653002501542653002301567653002401590653001501614653001901629100002101648700001801669856012701687 2012 eng d a0025-540800aEffects of grain morphology, microstructure and dispersed metal cocatalyst on the photoreduction of water over impurity-doped LaInO30 aEffects of grain morphology microstructure and dispersed metal c aTHE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLANDbPERGAMON-ELSEVIER SCIENCE LTDcMAY a1217-12280 v473 a

The single phase lanthanum indates doped with Ga (for La) and N (for O), i.e. La1-xGaxInO3 (0 <= x <= 0.2) and LaInO1-yNy (y similar to 0.6), exhibit significant activity for photoreduction of water; the yield of H-2 produced depending on dopant, excitation source, and addition of a sacrificial reagent. The two-step H-2 evolution observed for this reaction corresponds with the two distinct absorbance regimes displayed by these materials, one in UV-region due to bandgap excitation and the other in visible region arising from the transitions involving sub-bandgap donor or acceptor energy states. The photocatalytic activity of these d(10) metal oxides increases on coating with a metal/metal oxide co-catalyst, gold exhibiting superior activity to Pt and NiO, irrespective of excitation source and sample composition. The preparation-controlled particle morphology, doping-induced lattice imperfections, and metal/semiconductor hetero-junctions are envisaged to play a key role in the absorption characteristics and photocatalytic water reduction activity of metal/LaInO3 nanocomposites. (C) 2012 Elsevier Ltd. All rights reserved.

10aCatalytic properties10aChemical synthesis10aElectron microscopy10aInterfaces10aSemiconductors1 aDhanasekaran, P.1 aGupta, N., M. uhttps://library.ncl.res.in/content/effects-grain-morphology-microstructure-and-dispersed-metal-cocatalyst-photoreduction-001906nas a2200217 4500008004100000022001400041245011800055210006900173260010600242300001400348490000700362520106600369653001101435653002401446653001901470653001801489653002001507100002101527700001801548856012201566 2012 eng d a0360-319900aFactors affecting the production of H-2 by water splitting over a novel visible-light-driven photocatalyst GaFeO30 aFactors affecting the production of H2 by water splitting over a aTHE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLANDbPERGAMON-ELSEVIER SCIENCE LTDcMAR a4897-49070 v373 a

A d(10) photocatalyst, GaFeO3 having a band gap of similar to 2.7 eV, exhibits significant activity for the overall splitting of water under visible light (>395 nm) irradiation, in the absence of sacrificial reagent or a noble metal co-catalyst. The doping of an anion led to considerable enhancement in activity, the S-doped catalysts displaying better activity compared to the samples containing nitrogen. Even though the H-2/O-2 yields were affected by preparation-dependent grain morphology, no direct relationship was observed between the photoactivity of a sample and its specific surface area. The techniques of HRTEM, SEM, XPS, Laser Raman, UV-visible and photoluminescence spectroscopy have enabled to demonstrate that, besides the grain morphology, certain lattice imperfections and microstructure may also play a crucial role in water splitting activity of a photocatalyst. The factors responsible for catalyst deactivation are examined. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

10aGaFeO310ahydrogen production10aMicrostructure10aPhotocatalyst10awater splitting1 aDhanasekaran, P.1 aGupta, N., M. uhttps://library.ncl.res.in/content/factors-affecting-production-h-2-water-splitting-over-novel-visible-light-driven-002286nas a2200169 4500008004100000022001400041245011100055210006900166260007100235300001600306490000800322520159100330100002101921700002401942700002401966856012601990 2012 eng d a1932-744700aVisible-light-induced photosplitting of water over gamma `-Fe4N and gamma `-Fe4N/alpha-Fe2O3 nanocatalysts0 aVisiblelightinduced photosplitting of water over gamma Fe4N and  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcJUN a12156-121640 v1163 a

The application of gamma'-Fe4N, a noble-metal-free, low-cost catalyst, in the photosplitting of neat water into stoichiometric amounts of H-2 and O-2 under visible-light irradiation is reported for the first time. The catalyst showed optical absorption and photoluminescence emission bands in the entire visible region. The photocatalytic water-splitting activity was wavelength-dependent, the quantum efficiency for H-2 evolution being ca. 1.7 and 0.7% at excitation wavelengths of 450 and 500 nm, respectively. Addition of electron donor/acceptor sacrificial reagents considerably affected the yield and stoichiometry of H-2 and O-2. At the same time, the product yield increased in a composition-dependent manner for (gamma'-Fe4N)(x) + (alpha-Fe2O3)(1-x) nanocomposites. This activity augmentation is ascribed to the better dispersion of the active component gamma'-Fe4N and also to the availability of more active surface sites at Fe4N/Fe2O3 contacts. Moreover, the proximity of the valence band potential of the component photosystems promotes the preferential transfer/entrapment of photoexcited hole carriers. We envisage that the defect/impurity-induced interband-gap energy states may play a vital role in these charge-transfer processes, leading thereby to more effective e(-)-h(+) separation and the enhanced rate of the water-splitting reaction. First-principles electronic structure analysis suggests that the extraordinary photocatalytic and optical properties of intermetallic gamma'-Fe4N may arise from the particle-size-dependent changes in electronic structure.

1 aDhanasekaran, P.1 aSalunke, Hemant, G.1 aGupta, Narendra, M. uhttps://library.ncl.res.in/content/visible-light-induced-photosplitting-water-over-gamma-fe4n-and-gamma-fe4nalpha-fe2o3-0