Amorphous Microporous Titania Modified with Platinum(IV) ChlorideA New Type of Hybrid Photocatalyst for Visible Light Detoxification

Abstract

Amorphous microporous metal oxides of titanium (AMM-Ti) modified with a few percent of a platinum(IV) halide have been prepared by a sol-gel procedure and characterized by various surface analytical methods. By these methods the metal salt is homogeneously distributed in an almost exclusively amorphous powder of high specific surface area (160-200 m 2 /g) and a pore size of 0.8 nm. From the coordination number of 4.3 and a Pt-Cl distance of 2.28 Å, as calculated from extended X-ray absorption fine structure results, we conclude that the platinum salt is present as PtCl 4 . The hybrid sample (Pt(IV)/AMM-Ti) catalyzes the photodegradation of 4-chlorophenol with visible light. Apparent disappearance quantum yields decrease from 8.6 × 10 -3 at 335 nm to 4.5 × 10 -3 at 366 nm and 2.8 × 10 -3 at 400 nm; lower values of 1.6 × 10 -3 and 1.3 × 10 -3 are found at 436 and 546 nm, respectively. The quantum yield at both 366 and 436 nm decreases linearly with the square root of the incident photon flux, suggesting increasing recombination of the photogenerated charge carriers. We postulate that the photocatalytic activity of Pt(IV)/AMM-Ti originates from local excitation of the platinum(IV) chloride chromophore, affording a halogen atom and Pt(III) as intermediate species. Charge-trapping by the titania matrix generates reducing and oxidizing surface sites from which subsequent photodegradation proceeds. Good photostability of Pt(IV)/AMM-Ti is demonstrated by repeated use of the photocatalyst.

Sulphur–TiO2 yolk–shell nanoarchitecture with internal void space for long-cycle lithium–sulphur batteries

“…S3). The ability of toluene to diffuse through the TiO 2 shell to partially dissolve sulphur indicates its porous nature, which is typical of amorphous TiO 2 prepared using sol-gel methods 36 . The average pore diameter was determined to be B3 nm using the BarrettJoyner-Halenda method, which corresponds to a mesoporous structure.…”

Characterization and photocatalytic activity of noble-metal-supported surface TiO2/SiO2

“…The atomic number ratio of Pt 0 to Pt 2+ is 47.06:52.934 (Table 1). Some studies have argued the influence of different valences of platinum on the activity of photocatalyst [12]. Different valence states of metal play important roles in affecting charge trapping, releasing and migration, recombination, and interfacial charge transfer, and thus the photocatalytic behavior.…”

Synthesis and characterization of anionic (IO₃^-) doped TiO₂ nanophotocatalyst with enhanced photocatalytic activity

“…Therefore, the study of modifying TiO 2 in order to reduce the electron-hole recombination and sensitization towards visible light is one of the most important topics in photocatalysis research. Until now, several strategies including the doping of TiO 2 with transition metal ions [15][16][17], the synthesis of reduced forms with TiO 2-x structure by the plasma treatment [18,19], anchoring organic dyes onto the surface of TiO 2 , and the doping of TiO 2 with anionic nonmetals have been investigated [20][21][22][23][24][25]. However, the photocatalytic activity of metal doping is impaired by thermal instability [26] and an increase in carrier-recombination facilities [27].…”