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

Jenny Schneider,*,† Masaya Matsuoka,‡ Masato Takeuchi,‡ Jinlong Zhang, Yu Horiuchi,‡ Masakazu Anpo,‡ and Detlef W. Bahnemann*,† †Institut fur Technische Chemie, Leibniz Universitaẗ Hannover, Callinstrasse 3, D-30167 Hannover, Germany ‡Faculty of Engineering, Osaka Prefecture University, 1 Gakuen-cho, Sakai Osaka 599-8531, Japan Key Lab for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, Shanghai 200237, China

Understanding TiO2 photocatalysis: mechanisms and materials.

Photoinduced reactivity of titanium dioxide

Fujishima and Honda (1972) demonstrated the potential of titanium dioxide (TiO2) semiconductor materials to split water into hydrogen and oxygen in a photo-electrochemical cell. Their work triggered the development of semiconductor photocatalysis for a wide range of environmental and energy applications. One of the most significant scientific and commercial advances to date has been the development of visible light active (VLA) TiO2 photocatalytic materials. In this review, a background on TiO2 structure, properties and electronic properties in photocatalysis is presented. The development of different strategies to modify TiO2 for the utilization of visible light, including non metal and/or metal doping, dye sensitization and coupling semiconductors are discussed. Emphasis is given to the origin of visible light absorption and the reactive oxygen species generated, deduced by physicochemical and photoelectrochemical methods. Various applications of VLA TiO2, in terms of environmental remediation and in particular water treatment, disinfection and air purification, are illustrated. Comprehensive studies on the photocatalytic degradation of contaminants of emerging concern, including endocrine disrupting compounds, pharmaceuticals, pesticides, cyanotoxins and volatile organic compounds, with VLA TiO2 are discussed and compared to conventional UV-activated TiO2 nanomaterials. Recent advances in bacterial disinfection using VLA TiO2 are also reviewed. Issues concerning test protocols for real visible light activity and photocatalytic efficiencies with different light sources have been highlighted.

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A review on the visible light active titanium dioxide photocatalysts for environmental applications

Human skin is a remarkable organ. It consists of an integrated, stretchable network of sensors that relay information about tactile and thermal stimuli to the brain, allowing us to maneuver within our environment safely and effectively. Interest in large-area networks of electronic devices inspired by human skin is motivated by the promise of creating autonomous intelligent robots and biomimetic prosthetics, among other applications. The development of electronic networks comprised of flexible, stretchable, and robust devices that are compatible with large-area implementation and integrated with multiple functionalities is a testament to the progress in developing an electronic skin (e-skin) akin to human skin. E-skins are already capable of providing augmented performance over their organic counterpart, both in superior spatial resolution and thermal sensitivity. They could be further improved through the incorporation of additional functionalities (e.g., chemical and biological sensing) and desired properties (e.g., biodegradability and self-powering). Continued rapid progress in this area is promising for the development of a fully integrated e-skin in the near future.

25th Anniversary Article: The Evolution of Electronic Skin (E-Skin): A Brief History, Design Considerations, and Recent Progress

The present work describes the synthesis of CdS/CdSSe glass nanocomposites and its characterization. A few glass compositions were optimized and the optimized host glass was remelted along with different semiconductors like CdS and CdSSe at high temperature. The CdS/CdSSe is present in amorphous state in the glass matrix. The thermal treatments have been carefully optimized to obtain well-defined uniform crystal growth of CdS and CdSSe. The glasses with optimized conditions were fabricated and characterized thoroughly using UV, TG/DTA and TEM. The shift in absorption edge to the longer wavelength with heat treatment implies the increase in the crystal size. The band gap has been increased with decrease in the particle size. Crystal size of semiconductors obtained by TEM was 2.5-5 nm for the glass showing absorption edge cut-off at 475 nm (CM-475).

Nanostructured CdS/CdSSe glass composite for photonic application

Synthesis of bismuth phosphate (BiPO4) nanocrystals in low melting phosphate glass and its optical and magneto-optical properties were investigated. The presence of BiPO4 nanoparticles was confirmed by X-ray diffractometry and Raman spectroscopy. The optical transmission spectra of the glass samples showed that the red shift in the absorption edge is due to the presence of BiPO4 nanoparticles in the glass. Faraday rotation tests on the glass nanocomposite showed a large increase in the Verdet constant caused by BiPO4 nanoparticles in the phosphate glass. The BiPO4-glass nanosystem showed a higher Verdet constant (21.2° T−1 cm−1), which was increased 3-fold compared with the Verdet constant of BK-7 glass (7.52° T−1 cm−1). The BiPO4 glass nanocomposite may have potential applications in magneto-optical devices.

Preparation and magneto-optical properties of stable bismuth phosphate nanoparticles in phosphate glass

Tantalum-containing metal oxides, well known for their efficiency in water splitting and H 2 production, have never been used in visible light driven photodecomposition of H 2 S and H 2 production. The present work is an attempt in this direction and investigates their efficiency. A mixed metal oxide, ZnFe 2 Ta 2 O 9 , with the inclusion of Fe 2 O 3 to impart color, was prepared by the conventional ceramic route in single- and double-calcinations (represented as ZnFe 2 Ta 2 O 9 -SC and ZnFe 2 Ta 2 O 9 -DC respectively). The XRD characterization shows that both have identical patterns and reveals tetragonal structure to a major extent and a minor contribution of orthorhombic crystalline system. The UV-visible diffuse reflection spectra demonstrate the intense, coherent and wide absorption of visible light by both the catalysts, with absorption edge at 650 nm, giving rise to a band gap of 1.9 eV. Between the two catalysts, however, ZnFe 2 Ta 2 O 9 -DC has greater absorption in almost the entire wavelength region, which accounts for its strong brown coloration than ZnFe 2 Ta 2 O 9 -SC when viewed by the naked eye. In photocatalysis, both catalysts decompose H 2 S under visible light irradiation (λ ≥ 420 nm) and produce solar H 2 at a much higher rate than previously reported catalysts. Nevertheless, ZnFe 2 Ta 2 O 9 -DC distinguishes itself from ZnFe 2 Ta 2 O 9 -SC by exhibiting a higher efficiency because of its greater light absorption. Altogether, the tantalum-containing mixed metal oxide proves its efficient catalytic role in H 2 S decomposition and H 2 production process also.

Visible Light Driven ZnFe 2 Ta 2 O 9 Catalyzed Decomposition of H 2 S for Solar Hydrogen Production

Herein, we report zinc silver antimonate (ZnAg3SbO4)/ZAS, a novel visible light active photocatalyst for hydrogen generation. The XRD pattern confirmed the formation of a highly crystalline single phase orthorhombic ZAS. The FESEM and TEM micrographs exhibited that the size of the nanoparticles are in the range ∼20–30 nm. An optical study showed a broad absorption edge from 400 to 1000 nm, with an estimated band gap of about ∼1.48 eV. Considering this ideal band gap, ZAS was used as a photocatalyst for the photodecomposition of H2S under visible light irradiation to produce hydrogen for the first time. We obtained the utmost hydrogen evolution i.e., ∼10 200 μmol h−1 g−1 for the naked ZAS (without a co-catalyst) catalyst under visible light, which is much higher than the earlier reported photocatalysts. Generally, in complex oxides of p-block metals, the bottom of the conduction band (CB) consists of the merely localized s and/or p orbitals which are largely dispersed. This large dispersion is responsible for a high electron mobility and extremely high photocatalytic activity. Therefore, a complex oxide (ZAS) of Ag, Zn and the p-block metal (Sb) is found to be a promising visible light active photocatalyst. This is the most stable, efficient and eco-friendly novel visible light active oxide photocatalyst for hydrogen production.

Bharat B. Kale

Papers

Nanostructured CdS/CdSSe glass composite for photonic application

Preparation and magneto-optical properties of stable bismuth phosphate nanoparticles in phosphate glass

Visible Light Driven ZnFe 2 Ta 2 O 9 Catalyzed Decomposition of H 2 S for Solar Hydrogen Production

Novel nanocrystalline zinc silver antimonate (ZnAg3SbO4): an efficient & ecofriendly visible light photocatalyst with enhanced hydrogen generation

Facilitated Lithium Storage in Hierarchical Microsphere of Cu2S‐MoS2 Ultrathin Nanosheets