Conditions Extrêmes et Matériaux : Haute Température et Irradiation

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J.A.Rengifo-Herrera, M.Blanco, J.Wist, P.Florian, L.R.Pizzio
TiO2 modified with polyoxotungstates should induce visible-lightabsorption and high photocatalytic activity through the formation ofsurface complexes
Appl. Catal. B-Environ. 189 99-109 (2016) [view,doi]

TiO2nanospherical particles prepared by the sol-gel method were modified with tungstophosphoric(TPA) and tungstosilicic acid (TSA) at 30% (w/w) and then annealed at 500◦C for 2 h. Materials werecharacterized by multitechniques, such as scanning electron microscopy with energy dispersive X-rayspectroscopy (SEM-EDX), FT-Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffrac-tion (XRD), diffuse reflectance spectroscopy (DRS),31P,1H and29Si magic angle spinning nuclear magneticresonance (MAS-NMR). Acidity and isoelectric point measurements were also performed. DRS resultsshowed evidence of visible light absorption of TiO2-TPA and TiO2-TSA. MAS-NMR, XPS and FT-Ramancharacterization revealed evidence of a strong interaction between the Keggin anion of TPA or TSA andTiO2surfaces, possibly promoted by the formation of surface heteropolyacid-TiO2complexes; the lattershould be responsible of its visible light absorption. Photocatalytic activity was evaluated in the degra-dation of malachite green (MG), a cationic triphenylmethane dye, and 4-chlorophenol (4-CP) aqueoussolutions under UV-A and visible light irradiations. Under UV-A light, TPA-TiO2and TSA-TiO2materialsshowed high photocatalytic activity towards MG degradation, even higher than that of TiO2P-25. When4-CP was degraded, TiO2P-25 exhibited higher photocatalytic activity. Under visible light irradiationand using the modified photocatalysts, malachite green oxidation was achieved, while 4-chlorophenolreached almost 20% of degradation. Mechanisms of photocatalytic oxidation either under UV-A or visibleirradiation are discussed.