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

Journal Article · Thu May 01 04:00:00 EDT 2014 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/J.JSSC.2014.03.002· OSTI ID:22334226

Elías, Verónica R.; Sabre, Ema V. ^[1]; Winkler, Elin L. ^[2]; Andrini, Leandro ^[3]; Requejo, Félix G. ^[3]; Casuscelli, Sandra G. ^[1]

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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)

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 a synergistic effect and to stabilize active Cr{sup 6+}/Cr{sup 5+}.

• OSTI ID: 22334226
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Vol. 213; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

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