The light fandango: Anatase and anatase–rutile composite TiO2 has been modified electronically with highly dispersed surface iron oxide species. The chemisorption–calcination cycle technique was used with [Fe(acac)3] as a precursor (acac=acetylacetonate), leading to pronounced visible‐light activity and a concomitant increase in activity under illumination with UV light (cb=conduction band, vb=valence band).

ATaO 3 (A = Li, Na, K) compound oxides exhibit photocatalytic activity for the reduction of CO 2 in the presence of H 2. Only CO gas was generated over all samples under photoirradiation. The photocatalytic activity was higher in the order corresponding to KTaO 3 , NaTaO 3 and LiTaO 3 (LiTaO 3 > NaTaO 3 > KTaO 3). The order of the photocatalytic activities was consistent with that of the E g (optical gap) values. After 24 h of photoirradiation, the amount of evolved CO reached 0.42 µmol•g-1 over LiTaO 3. TPD experiments indicated that the broad peak which is assigned to chemisorbed CO 2 gas was observed at 573 K in the case of LiTaO 3. On the contrary, there was no peak in the spectra of NaTaO 3 and KTaO 3. The amount of evolved CO gas almost strongly depends on amount of chemisorbed CO 2 in the case of ATaO 3 (A = Li, Na, K). In addition, the photocatalytic activity increased with increasing the calcination temperature of LiTaO 3. This means that a smooth charge separation in a LiTaO 3 photocatalyst and chemisorption of CO 2 on the surface contribute to effective reduction of CO 2 in the presence of H 2. Teramura et al. Photocatalytic reduction of CO 2 over ATaO 3 4 / 21

It is the first report to observe the real-time behavior of photodeposition and the continuous structural change of Rh metal particles anchored on a TiO2 photocatalyst from an aqueous solution of Rh trivalent ions in the liquidsolid suspension by an in situ time-resolved energy-dispersive X-ray absorption fine structure (DXAFS) analysis. The DXAFS analysis uncovered that the Rh trivalent ions are adsorbed on the surface of the TiO2 photocatalyst, followed by reducing to the Rh metal particles by acceptance of electrons because the coordination number of a RhRh bond evaluated by the Fourier transforms of EXAFS spectra and the amount of the Rh trivalent ions determined by the ICP analysis linearly increased and decreased with elongation of photoirradiation time, respectively. The generation rates of the Rh metal particles and the diminution rates of the Rh trivalent ions depended on the type of sacrificial reagents and tends to become slower in the order corresponding to methanol > ethanol ≫ 1-propanol >2-propanol. The coordination number of a RhRh bond stopped increasing after 90 min of photoirradiation in the case of methanol. The coordination number was evaluated to 10, although that of Rh foil is 12, suggesting the generation of Ultrafine Rh particles on TiO2.

The photodeposition process of Rh metal nanoparticles on a TiO(2) photocatalyst from RhCl(3) aqueous solution in the presence of methanol as a sacrificial oxidant, which consists of the direct reduction of Rh(3+) ions to Rh metal and the formation of Rh nanoparticles, was uncovered by in situ time-resolved energy-dispersive X-ray absorption fine structure (DXAFS) analysis in a liquid-solid suspension state. The fractions of Rh metal particles and Rh(3+) precursor were estimated by the least-squares fitting of each X-ray absorption near-edge structure (XANES) spectrum by a linear combination of authentic spectra corresponding to Rh(0) and Rh(3+). The fraction of Rh metal linearly increased with photoirradiation time and saturated after 90 min of photoirradiation. The coordination number (Rh-Rh pair) was evaluated by the curve fitting of the Rh-Rh scattering at 2.45 A in the Fourier transforms (FT) of extended XAFS (EXAFS) spectra. The coordination number linearly increased with photoirradiation time and attained a constant value of 10 after 90 min of photoirradiation. This value is lower than that for the Rh foil (12). These suggest the formation of fine Rh metal nanoparticles on TiO(2). In addition, the diminution rate of Rh(3+) as determined by ICP analysis was in good agreement with the increased rates for the fraction of Rh metal particles estimated by XANES spectra and the coordination number (Rh-Rh pair) evaluated by FT-EXAFS spectra. This result strongly supports the fact that electrons generated by charge separation reduce the Rh(3+) precursor to an Rh metal particle at a moment in time and at a constant rate. The Rh particles do not grow in incremental steps, but Rh particles with a uniform size appear one after another on the surface.