Titania hollow spheres modified with tungstophosphoric acid with enhanced visible light absorption for the photodegradation of 4-chlorophenol

MARÍA DE LOS ÁNGELES ORELLANA; LILIAN OSIGLIO; PABLO M ARNAL; LUIS R. PIZZIO,

Photochemical and Photobiological Sciences

ROYAL SOC CHEMISTRY

Lugar: CAMBRIDGE; Año: 2017

1474-905X

Titania hollow spheres were synthesized using silica nanospheres as template. The core was removed using NaOH solution.They were subsequently impregnated with tungstophosphoric acid (TPA) solutions and annealed at two differenttemperatures (100 and 500 °C). These materials were characterized by several physicochemical techniques (XRD, BET,SEM, DRS, FT-IR, FT-Raman and 31P MAS-NMR). The 31P MAS-NMR and FT-IR characterization showed that the main speciespresent in the samples is the [PW12O40]3- anion, which was partially transformed into [P2W21O71]6- anion during thesynthesis and drying step. 31P MAS-NMR, and FT-Raman characterization revealed evidence of a strong interactionbetween the Keggin anion of TPA and TiO2 surfaces, possibly due to the formation of surface heteropolyacid-TiO2complexes. The DRS results showed that the absorption threshold onset continuously shifted to the visible region withincreased TPA concentration and calcination at 500 °C. The enhanced visible light absorption could be related to theformation of a surface complex TPA Keggin anion-TiO2. The catalytic activity of the materials in the photodegradation of 4-chlorophenol under UV and visible light irradiations increased when the TPA content and the calcination temperature ofthe samples were raised.