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

Generations Yi Ma,† Xiuli Wang,† Yushuai Jia,† Xiaobo Chen,‡ Hongxian Han,*,† and Can Li*,† †State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences and Dalian National Laboratory for Clean Energy, 457 Zhongshan Road, Dalian 116023, China ‡Department of Chemistry, College of Arts and Sciences, University of Missouri-Kansas City, 5100 Rockhill Road, Kansas City, Missouri 64110, United States

Titanium dioxide-based nanomaterials for photocatalytic fuel generations.

Hydrogen (H2) production via photocatalytic water splitting is one of the most promising technologies for clean solar energy conversion to emerge in recent decades. The achievement of energy production from water splitting would mean that we could use water as a fuel for future energy need. Among the various photocatalytic materials, titanium dioxide (TiO2) is the dominant and most widely studied because of its exceptional physico-chemical characteristics. Surface decoration of metal/non-metal on TiO2 nanoparticles is an outstanding technique to revamp its electronic properties and enrich the H2 production efficiency. Metal dopants play a vital role in separation of electron-hole pairs on the TiO2 surface during UV/visible/simulated solar light irradiation. In this paper, the basic principles, photocatalytic-reactor design, kinetics, key findings, and the mechanism of metal-doped TiO2 are comprehensively reviewed. We found that Langmuir-Hinshelwood kinetic model is commonly employed by the researchers to demonstrate the rate of H2 production. Copper (Cu), gold (Au) and platinum (Pt) are the most widely studied dopants for TiO2, owing to their superior work function. The metal dopants can amplify the H2 production efficiency of TiO2 through Schottky barrier formation, surface plasmon resonance (SPR), generation of gap states by interaction with TiO2 VB states. The recent advances and important consequences of 2D materials, perovskites, and other novel photocatalysts for H2 generation have also been reviewed.

Photocatalytic hydrogen production using metal doped TiO2: A review of recent advances

Considering the previous work on layered double hydroxides (LDHs) as novel photocatalysts, research on this group of materials has become one of the most exciting subjects of today. LDH has become an important class of layered materials having prospects in photocatalysis, wherein great attention has been paid to the exhaustive aerobic degradation of pollutants, photocatalytic water splitting, and CO2 photo-reduction. The unique structure, uniform distribution of different metal cations in the brucite layer, surface hydroxyl groups, flexible tunability, intercalated anions with interlayer spaces, swelling properties, oxo-bridged linkage, and high chemical stability are some of the important advantages of this group of materials. This article provides an up-to-date review on significant progress in the fabrication of LDH photocatalytic systems aiming at environmental clean-up and energy production, such as degradation of pollutants, photocatalytic H2 generation and photocatalytic CO2-reduction. This article, after discussing the recent significant progress in the synthesis of different photoactive LDH materials and photocatalytic applications through their structural and electronic properties, considers many typical examples. In particular, recent progress on the emerging strategies of LDH to improve their photocatalytic activity is also presented. Eventually, the future challenges and outlooks for this group of materials are also discussed.

A review on the recent progress, challenges and perspective of layered double hydroxides as promising photocatalysts

Because of their relatively high efficiency, high photostability, abundance, low cost, and nontoxic qualities, titania-based photocatalysts are still the most extensively studied materials for the photocatalytic production of hydrogen from water. The effects of the chemical and physical properties of titania, including crystal phase, crystallinity, particle size, and surface area, on its photoactivity towards hydrogen generation have been identified by various investigations. The high overpotential for hydrogen generation, rapid recombination of photogenerated electrons and holes, rapid reverse reaction of molecular hydrogen and oxygen, and inability to absorb visible light are considered the most important factors that restrict the photoactivity of titania, and strategies to overcome these barriers have been developed. These issues and strategies are carefully reviewed and summarized in this Minireview. We aim to provide a critical, up-to-date overview of the development of titania-based photocatalysts for hydrogen production, as well as a comprehensive background source and guide for future research.

Hydrogen production over titania-based photocatalysts

Hydrogen production by photocatalytic water-splitting using Cr- or Fe-doped TiO2 composite thin films photocatalyst

Physically and chemically synthesized TiO2 composite thin films for hydrogen production by photocatalytic water splitting

Efficient indium tin oxide/Cr-doped-TiO2 multilayer thin films for H2 production by photocatalytic water-splitting

Efficient H2 production by water-splitting using indium–tin-oxide/V-doped TiO2 multilayer thin film photocatalyst

Photocatalytic reaction of activated TiO 2 can be directly used for water splitting to produce hydrogen for fuel cell. TiO 2 thin films have been deposited using sol–gel method and subsequently heat-treated at 500 °C to form anatase phase. Ar + or N + ions with energy of 30 keV were implanted in anatase TiO 2 thin films with different ion doses in order to modify the band gap for visible light absorbance. UV–Vis spectroscopy was used to check the efficiency for absorbing visible light while structural and surface modifications caused by implantation were studied by using FT-IR and SEM respectively in the TiO 2 films. The ion-beam modified samples were found to be more efficient to absorb visible light in comparison to pure TiO 2 films. This efficiency of absorption increases with the implantation dose without any structural changes studied from FT-IR analysis. Ar + ions caused the formation of defect energy levels in the band gap while N + ions efficiently narrowed the band gap of TiO 2 thin film in the visible light region. The results are further discussed in terms of defect formation caused by ion implantation.

R. Dholam

Papers

Hydrogen production by photocatalytic water-splitting using Cr- or Fe-doped TiO2 composite thin films photocatalyst

Physically and chemically synthesized TiO2 composite thin films for hydrogen production by photocatalytic water splitting

Efficient indium tin oxide/Cr-doped-TiO2 multilayer thin films for H2 production by photocatalytic water-splitting

Efficient H2 production by water-splitting using indium–tin-oxide/V-doped TiO2 multilayer thin film photocatalyst

Low energy ion-beam modification of TiO2 photocatalyst thin film for visible light absorption