New Route to Synthesize Highly Active Nanocrystalline Sulfated Titania−Silica:  Synergetic Effects between Sulfate Species and Silica in Enhancing the Photocatalysis Efficiency

Abstract

A simple and efficient approach has been set up for fabricating highly active sulfated titania-silica (SO(4)(2-)/TiO(2)-SiO(2)): Ti(SO(4))(2) was hydrolyzed in the presence of silica, making it possible to sulfate titania and form titania-silica mixed oxide in one step. This study was focused on investigating the roles of sulfate species and silica in improving the physicochemical properties and photoactivity of SO(4)(2-)/TiO(2)-SiO(2) through comparison with sulfated titania (SO(4)(2-)/TiO(2)) and sulfate-free catalysts (TiO(2) and TiO(2)-SiO(2)). Various characterization methods, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and surface photovoltage spectroscopy (SPS), were employed to test these materials. The results revealed that for SO(4)(2-)/TiO(2) and TiO(2)-SiO(2) the sole presence of either sulfate species or silica imposes negative effects on the photocatalysis behavior of titania, leading them to have negligible photoactivities. On the contrary, in the case of SO(4)(2-)/TiO(2)-SiO(2), sulfate species and silica were proved to act in a cooperative manner; therefore, the following enhanced structure and surface properties of SO(4)(2-)/TiO(2)-SiO(2) were obtained: (i) relatively well-crystallized and smaller-size (15.4 nm) anatase-phase titania was formed upon 500 degrees C calcination without forming rutile phase and (ii) the formation of active surface sulfate species promotes the separation of photoinduced electron-hole pairs and therefore accelerates the photocatalysis reaction. Therefore, its photoactivity is enhanced as a result of the favorable synergic effects between sulfate species and silica due to their simultaneous presence.

Black Si-doped TiO2 nanotube photoanode for high-efficiency photoelectrochemical water splitting

“…It could be tted into Ti-O (529.6 eV), Si-O (530.4 eV) and oxygen vacancy (531.6 eV), respectively. 36,37 The result further conrmed that oxygen vacancies formed together with Ti 3+ states, i.e., both of them coexisted in the black Ti-Si-O nanotubes.…”

Visible-light-responsive sulfated vanadium-doped TS-1 with hollow structure: Enhanced photocatalytic activity in selective oxidation of cyclohexane

“…This can be attributed to the fact that V and S ions are incorporated into the HTS lattice and influence the local chemical state of Ti 4+ ions. It is obvious that the Ti2p region of VOSO 4 -modified HTS can be resolved into three parts, one at 460.1 eV originating from Ti 4+ species, the second at 459.2 eV resulting from VOSO 4 -modified HTS combined with the surface sulfate species [42], and the third at 457.2 eV corresponding to Ti 3+ species. As a result, the reduction of these Ti 4+ to Ti 3+ in the framework with tetrahedral coordination indicates that oxygen vacancies can be created by V and S doping.…”

PHOSPHORUS PROMOTED SO4(2-)/TiO2 SOLID ACID CATALYST FOR ACETALIZATION REACTION

“…Yang et al have reported that the sulfate species and silica species could work together to increase the acidity and catalytic activity of SO 4 2-/TiO 2 catalyst. 13 Thus, it can be concluded that the sulfate species and phosphorus species may also have the similar synergetic effects, which is responsible for the high catalytic activity of SO 4 2-/TiO 2 -P catalyst. Due to the disfavored kinetics of the biphasic catalytic system, the heterogeneous catalyst usually was not as active as the homogeneous catalyst.…”