There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Titanium Dioxide Nanomaterials: Synthesis, Properties, Modifications, and Applications

This critical review shows the basis of photocatalytic water splitting and experimental points, and surveys heterogeneous photocatalyst materials for water splitting into H2 and O2, and H2 or O2 evolution from an aqueous solution containing a sacrificial reagent Many oxides consisting of metal cations with d0 and d10 configurations, metal (oxy)sulfide and metal (oxy)nitride photocatalysts have been reported, especially during the latest decade The fruitful photocatalyst library gives important information on factors affecting photocatalytic performances and design of new materials Photocatalytic water splitting and H2 evolution using abundant compounds as electron donors are expected to contribute to construction of a clean and simple system for solar hydrogen production, and a solution of global energy and environmental issues in the future (361 references)

Heterogeneous photocatalyst materials for water splitting

2.3. Evaluation of Photocatalytic Water Splitting 6507 2.3.1. Photocatalytic Activity 6507 2.3.2. Photocatalytic Stability 6507 3. UV-Active Photocatalysts for Water Splitting 6507 3.1. d0 Metal Oxide Photocatalyts 6507 3.1.1. Ti-, Zr-Based Oxides 6507 3.1.2. Nb-, Ta-Based Oxides 6514 3.1.3. W-, Mo-Based Oxides 6517 3.1.4. Other d0 Metal Oxides 6518 3.2. d10 Metal Oxide Photocatalyts 6518 3.3. f0 Metal Oxide Photocatalysts 6518 3.4. Nonoxide Photocatalysts 6518 4. Approaches to Modifying the Electronic Band Structure for Visible-Light Harvesting 6519

Semiconductor-based Photocatalytic Hydrogen Generation

TiO2 photocatalysis and related surface phenomena

Visible light-responsive TiO2 thin film photocatalysts (Vis-TiO2) have been prepared on Ti metal foil (Vis-TiO2/Ti) or ITO glass (Vis-TiO2/ITO) substrates by a radio-frequency magnetron sputtering (RF-MS) method. The UV–Vis spectra as well as photoelectrochemical performance of Vis-TiO2 were affected by various calcination treatments such as calcination in air or NH3. Calcination treatment in NH3 (1.0 × 104 Pa, 673 K) was particularly effective in increasing the visible light absorption of Vis-TiO2 as well as in enhancing its photoelectrochemical performance and photocatalytic activity. A novel Vis-TiO2 thin film photocatalyst (Vis-TiO2/Ti/Pt) was prepared by an RF-MS method where Vis-TiO2 was deposited on one side of a Ti metal foil substrate and nanoparticles of Pt were deposited on the other side. The separate evolution of H2 and O2 from H2O could be successfully achieved by using an H-type glass cell consisting of two aqueous phases separated by Vis-TiO2/Ti/Pt and a proton-exchange membrane. It was found that the rate of the separate evolution of H2 and O2 was also dramatically enhanced by calcination treatment of Vis-TiO2 in NH3.

Separate evolution of H2 and O2 from H2O on visible light-responsive TiO2 thin film photocatalysts prepared by an RF magnetron sputtering method

Cu + /(SiO 2 /Al 2 O 3 ), Cu + /Al 2 O 3 and Cu + /SiO 2 catalysts were prepared by a combination of the ion-exchange method and thermovacuum treatment. In-situ XANES and EXAFS investigations of the catalysts have revealed that Cu + ions are anchored onto Al 2 O 3 or SiO 2 as planar 3-coordinate Cu + , while being anchored onto SiO 2 /Al 2 O 3 as linear 2-coordinate Cu + . Photoluminescence measurements of the catalysts and their quenching by the addition of N 2 O indicated that the Cu + ions interact with N 2 O in their photo excited state (3d 9 4s 1 ). UV irradiation of the catalysts in the presence of N 2 O led to the formation of N 2 and O 2 at 298 K, indicating that the photocatalytic decomposition of N 2 O proceeds on the Cu + ion catalysts. Reaction proceeds more efficiently on the Cu + /(SiO 2 /Al 2 O 3 ) catalyst than on the Cu+/Al 2 O 3 or Cu + /SiO 2 catalysts, suggesting that the 2-coordinate Cu + species show the higher activity for the photocatalytic decomposition of N 2 O than the 3-coordinate Cu + species.

/pdf/local-structures-of-copper-ion-catalysts-anchored-onto-4aquh98t0c.pdf

Local Structures of Copper Ion Catalysts Anchored onto Various Oxide Supports and their Photocatalytic Reactivities for the Decomposition of N2O at 298 K. In Situ XAFS, Photoluminescence, EPR Investigations

Vanadium ion-containing mesoporous molecular sieves V-MCM-41 were successfully prepared using a photo-assisted synthesis method with UV irradiation of the starting solutions at room temperature. Important advantages such as a shortened synthesis reaction time could be seen, leading to highly ordered regularly oriented pore structures for the V-MCM-41, when compared with synthesis using conventional method.

Photo-assisted synthesis of V-MCM-41 under UV light irradiation

A cyclopentadienyl ruthenium(II) complex has been immobilized on MCM-41 modified with aminopropyl group through an amide bond formation reaction FT-IR and UV–vis spectra show successful immobilization of cyclopentadienyl ruthenium complex onto the mesoporous silica surface by utilizing the amino group as a connector The coordination state of the ruthenium complex is analyzed in detail by XAFS measurements, which indicate that the immobilization process does not influence its coordination geometry Moreover, the retaining of long range ordering of the mesoporous structure of MCM-41 after grafting is evident from the results of XRD and N2 adsorption–desorption measurements The resulting material promotes efficiently the hydrosilylation of 1-hexyne to produce vinylsilane with high α-selectivity under UV-irradiation at room temperature Furthermore, the catalyst is recyclable for several catalytic runs without significant loss of its catalytic activity

A heterogeneous mesoporous silica-supported cyclopentadienyl ruthenium(II) complex catalyst for selective hydrosilylation of 1-hexyne at room temperature

Bipyridine derivatives were covalently anchored on the surface of the mesopores of MCM-41 porous material and the further introduction of Ag+ ions led to the formation of Ag+ bipyridine complexes by the chelation of the Ag+ ions with the bipyridine units. The successful covalent immobilization of the bipyridine derivatives as well as the Ag+ bipyridine complexes has been confirmed by various spectroscopic investigations such as FT-IR, UV-vis, and XPS analyses. It was found that the anchored bipyridine derivatives on the surface of MCM-41 prevent the reduction and agglomeration of the Ag+ species even after evacuation treatment at 573 K. Thus, the anchored Ag+ ions chelated with the bipyridine units inside the mesopores of MCM-41 were observed to exhibit photocatalytic reactivity for N2O reduction with CO.

Masaya Matsuoka

Papers

Separate evolution of H2 and O2 from H2O on visible light-responsive TiO2 thin film photocatalysts prepared by an RF magnetron sputtering method

Local Structures of Copper Ion Catalysts Anchored onto Various Oxide Supports and their Photocatalytic Reactivities for the Decomposition of N2O at 298 K. In Situ XAFS, Photoluminescence, EPR Investigations

Photo-assisted synthesis of V-MCM-41 under UV light irradiation

A heterogeneous mesoporous silica-supported cyclopentadienyl ruthenium(II) complex catalyst for selective hydrosilylation of 1-hexyne at room temperature

Synthesis of the Ag+-Bipyridine Complexes Anchored within MCM-41 and their Photocatalytic Reactivity for N2O Reduction with CO