Mesoporous SiO₂-Modified Nanocrystalline TiO₂ with High Anatase Thermal Stability and Large Surface Area as Efficient Photocatalyst

Abstract

Mesoporous SiO2-modified nanocrystalline TiO2 photocatalysts have been prepared by sol-hydrothermal processes, followed by post-treatment with appropriate amount of surfactant F127-modified silica sol. The resulting photocatalysts were also characterized by X-ray diffraction, Raman spectroscopy, Brunauer−Emmett−Teller spectroscopy, N2 adsorption−desorption, transmission electron microscopy, FT-IR, X-ray photoelectron spectroscopy, UV−vis diffuse reflectance spectroscopy, steady state surface photovoltage (SS-SPV), and transient state surface photovoltage (TS-SPV) techniques. The photocatalytic activities of the samples were evaluated by degrading rhodamine B solution under simulated solar illumination. The results show that the surface modification with mesoporous SiO2 greatly enhances the thermal stability of the nanocrystalline anatase TiO2, even still being with a main anatase phase after calcination at 900 °C, and the more is the amount of SiO2 used, the more obvious is the ehancement in the thermal stability. This enhancement is attributed to the effective inhibition of the direct contacts and the diffusions among anatase nanocrystals as well as to the retardation of the crystallite growth. Interestingly, the proper amount of mesoporous SiO2-modified nanocrystalline TiO2 samples by thermal treatment at high temperature can exhibit much higher photocatalytic activity than the commercial-available P25 TiO2, which is explained mainly by the high photoinduced charge carrier separation rate resulting from the high anatase crystallinity based on the analyses of SS-SPV and TS-SPV responses and the large surface area related to the small nanocrystallite size and mesoporous SiO2 as well as still possessing a certain amount of surface hydroxyl group.

The highly enhanced visible light photocatalytic degradation of gaseous o -dichlorobenzene through fabricating like-flowers BiPO 4 /BiOBr p-n heterojunction composites

“…The SPV method, which is a well-established technique to characterize the semiconductors, could indicate effective spatial separation properties of photo-induced carrier under monochromic excitation [51,52]. In general, the stronger is a SPV response signal, the higher is separation efficiency of photoinduced electron-hole pairs under the illuminated condition.…”

Characterization of Allophane from Gamalama Volcanic Soil, North Maluku, Indonesia

“…The OH vibrations of water molecules those are still trapped within the framework of allophane is indicated by absorption at 1635 cm -1 [9]. Vibration at 1033,85 and 586 cm -1 , respectively is an absorption for the Si-O-Al and Si-OAl in octahedral framework [10][11][12]. Absorption peak at 470,63 cm -1 which is absence in volcanic ash-soil, indicated peculiar wall structure of allophane ((HO) Si (OAL)3) [13].…”

Synthesis of doubly functional nanowhiskers from a colloid solution including a V–Ti complex precursor

“…Although the (011) peak is strong, several other orientations are observed, indicating a polycrystalline nature. The XRD peaks of pure TiO 2 at 2h = 25.28°and 2h = 27.40°are often taken as the characteristic peaks of anatase (101) and rutile (110) crystal phase, respectively [33]. The mass percentage of anatase phase in the TiO 2 samples can be estimated from the respective integrated characteristic XRD peak intensities using the quality factor ratio of anatase to rutile (1.34).…”