Tungsten oxide loaded with nanoparticulate platinum is demonstrated to exhibit high activity for the decomposition of organic compounds both in liquid and gas phases; the activity was almost comparable to that of TiO2 under UV light irradiation and much higher than that of nitrogen-doped TiO2 under visible irradiation.

Anatase titanium(IV) oxide (TiO2) particles with specific exposed crystal faces were prepared by hydrothermal treatment of peroxo titanic acid (PTA) solution with polyvinyl alcohol as a shape-control reagent. Crystal phase, shape, and size of TiO2 particles were found to be greatly dependent on pH value of PTA solution and time of hydrothermal treatment. TiO2 particles prepared from PTA solution of pH 7 had {101} and {001} exposed crystal faces, and the shape of TiO2 particles changed with the time of hydrothermal treatment. The prepared TiO2 particles with specific exposed crystal faces showed higher photocatalytic activity for acetaldehyde decomposition than commercial spherical TiO2 particles. This result implies that back reaction was prevented by spatial separation of redox sites in the particles because of selective migration of electrons and positive holes to specific exposed crystal faces and/or different reactivity of electrons and positive holes on the specific exposed crystal face. Furthermore, the shape evolution of TiO2 particles showed a relationship with photocatalytic activity, and a stacked structure of octahedral anatase showed the highest photocatalytic activity due to both oxidation and reduction sites with large surface area.

Correlation between structural and physical properties and photocatalytic activities for five kinds of reactions of 35 titania samples was obtained through multivariable analyses: photocatalytic activities were empirically reproduced by a linear combination of six properties with fair reliability. While a portion of results could be interpreted using a conventional mechanism, significant activity dependence on properties, not disclosed yet, was suggested.Photocatalytic reaction is induced by photoexcited electrons (e À ) and positive holes (h þ ) generated in a solid photocatalyst followed by redox reaction with surface-adsorbed substrates. Titanium(IV) oxide (titania) is one of the most promising photocatalysts because of its high chemical stability, sufficient energy of its e À and h þ to drive various photocatalytic reactions, negligible toxicity, inexpensiveness, and ease of preparation. Only one plausible weakness of the titania photocatalyst is that it absorbs only ultraviolet light, though such transparency is preferable when titania is coated on colored materials. It is known that the photocatalytic activity, i.e., rate of photocatalytic reaction, depends on the structural and physical properties of titania. It is believed that there is a relationship between properties and activities, i.e., a structure-activity correlation. It has often been claimed that the smaller the particle size, i.e., the larger the specific surface area, the higher the photocatalytic activity or that anatase is better than rutile.1 However, such discussion on the correlations has been limited to a certain series of samples prepared in a similar way or small number of commercial samples, 2 and there seem no comprehensive correlations.The present study aims at obtaining the structure-activity correlations for a large number of titania photocatalysts covering commercially available titania samples in Japan (see Table S1) 14 by statistical multivariable analysis. Five representative reactions were chosen, and their relative rates were analyzed using six properties, 3 specific surface area (BET), density of lattice defects (DEF), primary (PPS) and secondary (SPS) particle size, and existence of anatase (ANA) and rutile (RUT) phases, to obtain intrinsic dependence of photocatalytic activities on the properties.Five test photocatalytic reactions were as follows: a, Oxygen (O 2 ) liberation and silver deposition from a deaerated aqueous silver sulfate solution; b, Dehydrogenation of methanol in a deaerated aqueous solution; c, Oxidative decomposition of acetic acid to liberate carbon dioxide (CO 2 ) from an aerated aqueous solution; d, Decomposition of acetaldehyde into CO 2 in air; and e, Synthesis of pipecolinic acid from L-lysine in a deaerated aqueous solution (see SI).First, the rates of reactions were compared with each structural property. In general, there were no significant relations between them, while, in some cases, dependence of the rate on a parameter was observed (see SI, Tables S2 and S4). This seems reasonable since the...

Here we propose a method for the identification of metal-oxide powders with the energy-resolved distribution of electron traps and conduction-band bottom position reflecting a surface structure and a bulk structure, respectively, as a fingerprint, based on the degree of coincidence for a given pair of samples, measured using newly developed reversed double-beam photoacoustic spectroscopy.