02431nas a2200253   4500008004100000022001400041245010900055210006900164260010600233300001600339490000700355520143700362653002801799653003001827653002701857653002301884653002701907653002001934100001601954700002401970700002601994700002502020856013202045       2014                        eng d  a0360-319900aGenesis of enhanced photoactivity of CdS/Ni-x nanocomposites for visible-light-driven splitting of water0 aGenesis of enhanced photoactivity of CdSNix nanocomposites for v  aTHE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLANDbPERGAMON-ELSEVIER SCIENCE LTDcNOV  a19424-194330 v393 a<p>A series of CdS/Ni-x nanocomposite photocatalysts, containing ca. 0.6-15 wt% Ni, were synthesized using a one-step hydrothermal method and characterized for their crystallographic, morphological, interfacial, and optical properties. Rietveld refinement of powder XRD data revealed the coexistence of wurtzite (hexagonal) and zinc blende (cubic) phases of CdS in ratios dependent on Ni content. Only a fraction of Ni existed as a secondary phase of NiS while the majority occupied the lattice positions of hexagonal CdS. Whereas up to 10-fold enhancement in H-2 evolution compared with pure CdS was observed for samples containing similar to 1.5-4.5 wt% Ni, samples with smaller or larger Ni content displayed poor activity for visible-light-induced splitting of water in presence of sulfide-sulphite ions as sacrificial electron donors. In contrary to recent findings, our study reveals that the enhanced CdS photoactivity is not a result of charge transfer between p-type NiS and n-type CdS, Ni-induced visible-region absorbance, or the coating of CdS particles by non-photoactive NiS. Instead, the preparation-dependent hexagonal/cubic CdS phase boundaries and particle morphology may play a crucial role. Additionally, certain Ni-doping-induced sub-bandgap shallow energy levels contribute to charge carrier separation. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.</p>10aCdS/Ni-x nanocomposites10aDominant hexagonal facets10aEnhanced photoactivity10aHydrogen evolution10aPhase boundary effects10awater splitting1 aDevi, Suman1 aKorake, Prakash, V.1 aAchary, Srungarpu, N.1 aGupta, Narencira, M.  uhttps://library.ncl.res.in/content/genesis-enhanced-photoactivity-cdsni-x-nanocomposites-visible-light-driven-splitting-water-002948nas a2200205   4500008004100000022001400041245014400055210006900199260011000268300001600378490000600394520208400400100001602484700002302500700001802523700002602541700002402567700002402591856012702615       2014                        eng d  a2046-206900aPhotophysical, bandstructural, and textural properties of o-FeNbO4 in relation to its cocatalyst-assisted photoactivity for water oxidation0 aPhotophysical bandstructural and textural properties of oFeNbO4   aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcJUL  a33435-334450 v43 a<p>In this study, a relationship between physicochemical, photophysical and photocatalytic properties of hydrothermally synthesized orthorhombic iron niobate (FeNbO4) is investigated. o-FeNbO4 displayed a multi-regime optical absorbance, which was ascribed to at least two distinct phenomena: (i) bandgap (similar to 3.4 eV) excitation giving rise to UV absorbance and (ii) energy transitions involving disorder-induced sub-bandgap donor or acceptor states leading to visible light absorbance. The preparation-dependent distortion in the crystal lattice and the existence of closely spaced inter-bandgap energy states were corroborated by powder X-ray diffraction, photoluminescence, thermoluminescence, and Raman spectroscopy studies. The first principles electronic structure elucidation and photoelectrochemical measurements supported a wide bandgap for FeNbO4, in contrast to the narrow bandgap reported previously. Correspondingly, a small photocurrent density was observed for FeNbO4 (similar to 2 to 3 mu A cm(-2)) under 1 sun illumination, suggesting the availability of a smaller cross section of photogenerated charge pairs. Following these band characteristics, while no H-2 evolution was observed, FeNbO4 gave rise to particle size-dependent O-2 evolution during visible light irradiation of water in the presence of electron scavengers, the samples loaded with NiO as cocatalyst showing better activity. Further, the transmission electron microscopy examination revealed the dominant exposure of (011) facets of FeNbO4, besides a significant heterogeneity of inter-domain boundaries. Overall, our results confirm that the photoactivity of metal/oxide nanocomposites is governed by a combination of factors, such as: grain morphology, microstructure, surface adsorption states, and the localized inter-bandgap energy states. Our study also reveals that, in contrast to prevalent assumptions, the wavelength at the absorption edge may not represent the true band-to-band energy gap of metal oxide semiconductors, which is relevant to their photocatalytic activity.</p>1 aBabu, Robin1 aKelkar, Sarika, A.1 aKashid, Vikas1 aAchary, Srungarpu, N.1 aSalunke, Hemant, G.1 aGupta, Narendra, M.  uhttps://library.ncl.res.in/content/photophysical-bandstructural-and-textural-properties-o-fenbo4-relation-its-cocatalyst-002339nas a2200169   4500008004100000022001400041245012700055210006900182260000900251300001400260490000700274520169100281100002401972700002601996700002402022856012302046       2015                        eng d  a0360-319900aRole of aliovalent cation doping in the activity of nanocrystalline CdS for visible-light-driven H-2 production from water0 aRole of aliovalent cation doping in the activity of nanocrystall  cJUL   a8695-87050 v403 a<p>This study was aimed at discerning the enhancement in the visible-light-driven water splitting activity of nanocrystalline CdS photocatalysts because of their doping with a small amount of an aliovalent cation (Ag+ or Cr3+). The CdS/Cr-x (x = 0-2.3 wt%) and CdS/Ag-x (x = 0-1.5 wt%) samples, which were synthesized using a one-step hydrothermal method, were characterized systematically for their crystallographic, morphological, interfacial, and photo-physical properties. The Rietveld refinement of the powder X-ray diffraction data enabled us to quantify the doping-effect on the phase composition and lattice parameters. As compared to pure CdS, the samples containing similar to 0.2 wt% of Cr or Ag showed two or tenfold enhancement in the rate of H-2 evolution from water, respectively, when sulfide-sulfite ions were used as sacrificial electron donors. This pyramidal trend, i.e. maximum activity for a specific impurity content, which decreased on decreasing as well as increasing the amount of doping, did not occur owing to the presence of a secondary-phase metal sulfide or a dispersed metal cocatalyst. Our study revealed that instead of the widely advocated mechanism involving inter-semiconductor or semiconductor-to-metal electron transfer steps, the doping-modified photoactivity of CdS was governed by certain bulk and surface properties such as the cation-dependent particle nucleation, dominance of hex-CdS facets, and structural defects. Additionally, impurity-induced sub-bandgap charge-trapping states also contributed to the overall quantum efficiency. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.</p>1 aKorake, Prakash, V.1 aAchary, Srungarpu, N.1 aGupta, Narendra, M.  uhttps://library.ncl.res.in/content/role-aliovalent-cation-doping-activity-nanocrystalline-cds-visible-light-driven-h-2