Suresh Palla

Synthesis, Characterization and Photocatalytic Activity of KAl0.33W1.67O6 and Sn0.5Al0.33W1.67O6xH2O

Nano sized defect pyrochlore, KAl0.33W1.67O6 (KAW), is prepared through sol–gel method. Divalent tin‐doped KAW is obtained at room temperature by ion exchange method using acidified SnCl2 and parent KAW. These materials are characterized by powder X‐ray diffraction, thermogravimetric analysis (TGA), scanning electron microscopy—energy dispersive spectra (SEM‐EDS), Raman Spectroscopy and X‐ray photo electronic spectroscopy. The composition of tin‐doped KAW is obtained from chemical analysis, SEM‐EDS and TGA methods and written as Sn0.5Al0.33W1.67O6 xH2O (x = 1.4–1.5) (SnAW). It crystallizes in cubic lattice with Fd3¯m space group. The band gap energies are found to be 2.82 and 2.21 eV for KAW and SnAW respectively. The observed reduction in the band gap with the introduction of Sn2+ in defect pyrochlore lattice is due to mixing of 5s state of Sn2+ with O 2p states leading to an upward shift in the valence band. The Raman spectra of these materials gave more bands than the number expected for defect pyrochlores due to substitutional disorder in 16c sites and displacive disorder of A ions. The photoactivity of SnAW is higher compared to KAW.

Metathesis synthesis, characterization, spectral and photoactivity studies of Ln2/3MoO4 (Ln=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er and Y)

Abstract Rare earth ortho-oxomolybdates of composition Ln2/3MoO4 (Ln=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er and Y) were prepared by metathesis reaction. All these materials were characterized by powder X-ray diffraction, Fourier transform-infrared spectroscopy (FT-IR) and UV-Vis diffuse reflectance spectra. The Rietveld analysis of all the samples was carried out to obtain the unit cell parameters and reliability factors. All the materials were crystallized in tetragonal lattice with I41/a space group. The infrared spectra of all the samples were characterized by bands due to MoO42– units. The bandgap energies of all the samples were obtained from UV-Vis DRS spectra. The luminescence spectra of Ln2/3MoO4 (Ln=Pr, Eu and Dy) showed characteristic transitions of the rare earth ions. The visible light photocatalytic activity of all the samples was studied against degradation of methylene blue.

Enhanced photoactivity of antimony phosphates by substitution of H+, Cu2+ and N3− in the K3Sb3P2O14·xH2O crystal lattice

Abstract Substitutional doping of framework heteroatoms in photocatalysis is one of the approaches for harvesting visible light. Tunnel structure potassium antimony phosphate (K3Sb3P2O14·xH2O) and Cu2+, H+ , and N3- substituted K3Sb3P2O14·xH2O were prepared. These materials were characterized by powder X-ray diffraction, energy dispersive spectra, infrared spectra, and UV–Vis diffuse reflectance spectra. All these compositions were crystallized in the rhombohedral crystal lattice with

Photocatalytic degradation of organic dyes with Sn2+- and Ag+-substituted K3Nb3WO9(PO4)2 under visible light irradiation

R\overline{3} m

Preparation, characterization and photocatalytic studies of K2Al2Ti6O16, K2−xAgxAl2Ti6O16 and K2Al2Ti6O16−xNy

R3¯m space group. The absorption edges of doped compositions were shifted to longer wavelength region considerably upon substitution of Cu2+, H+ , and N3−. The photocatalytic activity of these materials was tested against the degradation of methyl violet. The higher visible light photocatalytic activity of doped K3Sb3P2O14·xH2O compositions compared to parent material was discussed. N3−-doped K3Sb3P2O14·xH2O photocatalyst is stable even after the fourth cycle of photodegradation.

Synthesis and Catalytic Performance of Na2HfM(PO4)3 and Ag2−xNaxHfM(PO4)3 (M = Fe and Al and 0.07 ≤ x ≤ 0.13)

ABSTRACT Trivalent bismuth substituted La2Zr2O7 pyrochlores of compositions La2-xBixZr2O7 (x = 0.2, 0.4 and 0.6) have been prepared by sol-gel method. All the samples were characterized by powder X-ray diffraction, IR spectroscopy, and SEM-EDS. These materials were found to crystallize in cubic lattice with space group . The unit cell parameters were deduced from the Rietveld refinement. The dc conductivity of all samples was measured in the temperature range 200–700°C. The photocatalytic activities of the samples were studied against methylene blue decomposition under sunlight. La2-xBixZr2O7 compounds showed enhanced photoactivity compared to La2Zr2O7.

Photocatalytic degradation of organic dyes with Sn 2+ - and Ag + -substituted K 3 Nb 3 WO 9 (PO 4 ) 2 under visible light irradiation

Abstract A tunnel structure compositions of Ag+- and Sn2+-substituted K3Nb3WO9(PO4)2 photocatalysts were synthesized by an ion exchange method and characterized by powder XRD, SEM–EDS, UV–Vis (DRS), BET and FT-IR. The ion-exchanged products are isomorphous with parent K3Nb3WO9(PO4)2. Absorption edges of Ag+- and Sn2+-doped K3Nb3WO9(PO4)2 samples were red shifted remarkably into the visible light region. Photocatalytic activity of these materials was evaluated by studying the degradation of methylene blue, methyl violet, methyl orange and rhodamine B dyes under visible light irradiation. The photocatalytic properties of these compounds were explained based on their band gap energies, photoluminescence spectra and the amounts of ·OH radicals generated during photocatalysis. The possible photocatalytic mechanistic pathway was discussed. The stability of all catalysts during photocatalytic experiment was also investigated. Graphical Abstract

Photocatalytic degradation of organic dyes with Sn2

Substitutional doping of framework heteroatoms in photocatalysts is one of the approaches for harvesting visible light. The present work aims to utilize the visible light for photocatalytic degradation of organic pollutant by tailoring the bandgap energy of Li2VPO6 through nitrogen doping. Li2VPO6 and N-doped Li2VPO6 are prepared by solid-state method. These materials were characterized by powder X-ray diffraction, energy-dispersive spectra, Raman spectra, UV–Vis diffuse reflectance spectra (UV–Vis DRS), and 31P MAS NMR. The absorption edge of N-doped Li2VPO6 is shifted to longer wavelength region considerably. The photocatalytic activity was tested against the degradation of methylene blue. The higher visible light photocatalytic activity of N-doped Li2VPO6 compared to pristine Li2VPO6 was discussed. The catalysts are stable even after fourth cycle of photodegradation.