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Title: Influence of the hydration by the environmental humidity on the metallic speciation and the photocatalytic activity of Cr/MCM-41

The influence of the environmental humidity on the Cr species deposited on inorganic supports like MCM-41 silicates was analyzed by UV–vis Diffuse Reflectance (UV–vis RD), Electronic Spin Resonance (ESR) and X-ray near-edge (XANES) spectroscopy. Metal speciation could be inferred, finding that prolonged exposure periods under environmental humidity provoked the reduction of the active Cr{sup 6+} species and thus, the decrease of the Cr/MCM-41 photoactivity. After the Ti loading over the Cr modified samples, Cr species and the photoactivity were not notably influenced by the humidity exposure. Thus, it could be concluded that the presence of Ti is important because the TiO{sub 2} cover protects the oxidized Cr species, stabilizing them. - Graphical abstract: The load of Ti on the Cr modified MCM-41 produces a TiO{sub 2} cover that protects the active Cr species from their reduction by the environmental humidity. - Highlights: • Spectroscopic analysis shows presence of Cr{sup 6+}/Cr{sup 5+} in calcined/re-calcined samples. • Cr{sup 3+} species increase for hydrated samples causing their photoactivity decrease. • Samples with high Cr loadings are more sensitive to environmental humidity presence. • TiO{sub 2} cover protects oxidized Cr species from their reduction by the water. • Ti is important to allow amore » synergistic effect and to stabilize active Cr{sup 6+}/Cr{sup 5+}.« less
Authors:
;  [1] ;  [2] ;  [3] ;  [3] ;  [4] ;  [1] ;  [1]
  1. Centro de Investigación y Tecnología Química (CITeQ) (UTN-CONICET), Maestro López esq. Cruz Roja Arg, Ciudad Universitaria, 5016 Córdoba (Argentina)
  2. Centro Atómico Bariloche, CNEA-CONICET, Bustillo 9500, 8400 S. C. de Bariloche (Argentina)
  3. Instituto de Fisicoquimica Teórica y Aplicada (INIFTA) (UNLP-CCT CONICET La Plata), 64 y Diag. 113, 1900 La Plata (Argentina)
  4. (Argentina)
Publication Date:
OSTI Identifier:
22334226
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 213; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ABSORPTION SPECTROSCOPY; CHROMIUM; CHROMIUM IONS; DEPOSITS; ELECTRON SPIN RESONANCE; HUMIDITY; PHOTOCATALYSIS; TITANIUM OXIDES; X RADIATION; X-RAY SPECTROSCOPY