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

It is known that 2D MXene can be oxidized in air to form heterostructures of carbides, carbon, and oxides. We prepared MXene/TiO2 nano-heterostructures by in-situ thermal processing of MXene (Ti3C2Tx) at 250–400 °C temperature range in air. The structural studies by x-ray diffraction indicate the formation of MXene/TiO2 nano-heterostructures with increasing the annealing temperature above 300 °C and the resulting structure became mostly TiO2 after 400 °C annealing with no detectable MXene peaks in XRD patterns. The diffuse reflectance UV–Visible absorbance spectroscopy shows the blue shift in the absorbance profile of MXene from 720 to 380 nm by increasing the temperature. Photoluminescence spectra shows two emission peaks, the emission at 370 nm and 470 nm corresponds to band edge emission and oxygen defect, respectively. Raman analysis also supports the formation of MXene and TiO2 nano-heterostructures. Scanning and transmission microscopy results depict the formation-layered structures of MXene transformed into exfoliated sheet-like structures due to etching. The photocatalytic activity of formed nano-heterostructures was investigated for H2 generation via water splitting and aqueous methylene blue dye degradation. The nano-heterostructure formed at 350 °C conferred highest H2 production (366 μmol/0.1 g) as compared to other prepared compositions having apparent quantum yield (AQY) of 5.9% and shows MB degradation rate of 13.16 × 10–3 min−1.The formation of nano-heterostructures, particle morphology, higher surface area, the presence of remaining MXene might be responsible for higher photocatalytic activity. These MXene-based nano-heterostructures will have potentials along with other semiconductors for enhanced hydrogen production.Graphical abstract Schematic presentation of photocatalytic water splitting using Ti3C2Tx/TiO2 nano-heterostructure. 

2D layered MXene/TiO2 nano-heterostructures for photocatalytic H2 generation

Computational analysis of a new airfoil for micro-capacity wind turbine

In this investigation, anatase nanocrystalline TiO2 (nc-TiO2) films are deposited by using sol-gel dip coating method on ITO substrates followed by annealing at 200, 300, 400 and 500 °C / 2 hr in air. To examine the structure and morphology of films, XRD, Raman spectroscopy, SEM and HRTEM techniques are used. The XRD studies showed the evolution of pure anatase TiO2 phase with average crystallite size = 12-15 nm in resultant films. The morphological studies using SEM and HRTEM indicated ~ uniform size distribution of spherical agglomerates in films and nanocrystalline state of films (average particle size ~ 20 nm) respectively. The optical properties calculated from UV-Visible transmission spectra are found to be indirect band gap energy = 3.20 eV, absorbance coefficient = 9.2 x 104 cm-1, transmittance = 88.5 %, refractive index = 2.12 and porosity ratio = 36.6 % for the 400 °C annealed film. The better photovoltaic performance: JSC = 2.34 mA/cm2, VOC = 0.562V, FF = 35.23 % & η = 0.46 % is obtained for eosin-Y dye sensitized solar cell made with 400 °C annealed film.

Bharat B. Kale

Papers

2D layered MXene/TiO2 nano-heterostructures for photocatalytic H2 generation

Computational analysis of a new airfoil for micro-capacity wind turbine

Effect of Temperature on Optical and Photovoltaic Properties of nc-TiO2 Thin Films for Dye Sensitized Solar Cell