Journal ArticleDOI
Photocatalytic activity of transition-metal-loaded titanium(IV) oxide powders suspended in aqueous solutions: Correlation with electron hole recombination kinetics
Shigeru Ikeda,Noboru Sugiyama,Bonamali Pal,Giuseppe Marcì,Leonardo Palmisano,Hidenori Noguchi,Kohei Uosaki,Bunsho Ohtani +7 more
TLDR
In this paper, the effect of recombination kinetics on photoactivity was discussed, and a simple kinetic model to explain the overall rate of these photocatalytic reactions was proposed, and the relationship between kr and the rate of CO2 production by unplatinized M-TiO2 under aerated conditions was ambiguous; other factor(s) might control the latter.Abstract:
Photocatalytic reactions by transition-metal (V, Cr, Fe, Co, Cu, Mo, or W) loaded TiO2 (M-TiO2) powders suspended in aqueous solutions of methanol, (S)-lysine (Lys), or acetic acid were investigated. The photoactivities of various samples were compared with the rate constant (kr) of recombination of photoexcited electrons and positive holes determined by femtosecond pump–probe diffuse reflection spectroscopy (PP-DRS). As a general trend, increased loading decreased the rate of formation of the main products (H2
, pipecolinic acid (PCA), and CO2) under UV (>300 nm) irradiation, and the effect became more intense on increasing the loading. In PP-DRS, these M-TiO2 gave similar decays of absorption at 620 nm arising from excitation by a 310 nm pulse (<100 fs). The second-order rate constant (kr) markedly increased with loading, even at a low level (0.3%) and further increased with an increase in loading up to 5%. The photocatalytic activity of platinized M-TiO2
for H2 and PCA production under deaerated conditions depended strongly on kr, but the relation between kr and the rate of CO2 production by unplatinized M-TiO2 under aerated conditions was ambiguous; other factor(s) might control the rate of the latter. These different kr dependences of photoactivity on the reaction kinetics governed by e−–h+ recombination were attributed to the presence of O2 and Pt deposits. A simple kinetic model to explain the overall rate of these photocatalytic reactions is proposed, and the effect of recombination kinetics on photoactivity is discussed.read more
Citations
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Catalysis with TiO2/Gold Nanocomposites. Effect of Metal Particle Size on the Fermi Level Equilibration
TL;DR: The size-dependent shift in the apparent Fermi level of the TiO(2)-Au composite shows the ability of Au nanoparticles to influence the energetics by improving the photoinduced charge separation.
Journal ArticleDOI
Anchoring semiconductor and metal nanoparticles on a two-dimensional catalyst mat. Storing and shuttling electrons with reduced graphene oxide.
TL;DR: The ability of RGO to store and shuttle electrons, as visualized via a stepwise electron transfer process, demonstrates its capability to serve as a catalyst nanomat and transfer electrons on demand to adsorbed species.
Journal ArticleDOI
Lewis acids as catalysts in oxidation reactions: from homogeneous to heterogeneous systems.
TL;DR: This review is focused on the use of solid Lewis acids to promote catalytic oxidations, and the core of the review is organized to show the evolution from the simplest strategy for heterogeneizing homogeneous catalysts, to the more elaborate ones in which the active sites are part of the solid structure.
Journal ArticleDOI
Preparation of Polycrystalline TiO2 Photocatalysts Impregnated with Various Transition Metal Ions: Characterization and Photocatalytic Activity for the Degradation of 4-Nitrophenol
A. Di Paola,Giuseppe Marcì,Leonardo Palmisano,Mario Schiavello,Kohei Uosaki,S. Ikeda,Bunsho Ohtani +6 more
TL;DR: A set of polycrystalline TiO2 photocatalysts loaded with various ions of transition metals (Co, Cr, Cu, Fe, Mo, V, and W) were prepared by using the wet impregnation method.
Journal ArticleDOI
Primary intermediates of oxygen photoevolution reaction on TiO2 (Rutile) particles, revealed by in situ FTIR absorption and photoluminescence measurements.
Ryuhei Nakamura,Yoshihiro Nakato +1 more
TL;DR: The results give strong support to the previously proposed mechanism that the oxygen photoevolution is initiated by a nucleophilic attack of a H2O molecule on a photogenerated hole at a surface lattice O site, not by oxidation of surface OH group by the hole.
References
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Effects of altervalent cation doping of titania on its performance as a photocatalyst for water cleavage
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