Hydrogen production from water splitting by photo/photoelectron-catalytic process is a promising route to solve both fossil fuel depletion and environmental pollution at the same time. Titanium dioxide (TiO2) nanotubes have attracted much interest due to their large specific surface area and highly ordered structure, which has led to promising potential applications in photocatalytic degradation, photoreduction of CO2, water splitting, supercapacitors, dye-sensitized solar cells, lithium-ion batteries and biomedical devices. Nanotubes can be fabricated via facile hydrothermal method, solvothermal method, template technique and electrochemical anodic oxidation. In this report, we provide a comprehensive review on recent progress of the synthesis and modification of TiO2 nanotubes to be used for photo/photoelectro-catalytic water splitting. The future development of TiO2 nanotubes is also discussed.

One‐dimensional TiO2 Nanotube Photocatalysts for Solar Water Splitting

Solar hydrogen generation via photocatalytic water splitting represents an attractive strategy to address the global energy crisis and environmental pollution issues. CdS-based photocatalysts, including nanosized CdS powder, CdS-based solid solutions and CdS quantum dots, have attracted significant attention for photocatalytic H2 production due to their unique advantages, including strong visible light absorption capacity, suitable band edge levels and excellent electronic charge transfer. This review focuses on recent advances in material design and technological aspects of CdS-based photocatalysts for applications in photocatalytic H2 production. A brief overview of basic concepts and principles of photocatalytic water splitting was given in the Introduction section, followed by the basic properties of CdS. Then, the utilization of three main types of CdS-based semiconductor photocatalysts for solar H2 generation is introduced, and those important factors which can determine the photocatalytic performance were also discussed in detail. Special consideration has been given to the effect of morphology, interfacial junctions, exposing facet and cocatalysts on the photocatalytic performance of CdS-based photocatalysts. Finally, a roadmap of possible future directions to further explore the research field of CdS-based photocatalysts for solar H2 generation is also discussed.

Cadmium sulfide-based nanomaterials for photocatalytic hydrogen production

Charge carrier trapping, recombination and transfer during TiO2 photocatalysis: An overview

Black TiO2 Nanomaterials: A Review of Recent Advances

The photocatalytic activity of TiO2 has aroused a broad range of research effort since 1972. Although TiO2 has a very high efficiency in utilizing ultraviolet light, its overall solar activity is very limited due to its wide bandgap (≈3.0−3.2 eV). This is a bottleneck for TiO2 to be applied in the areas ranging from visible-light photocatalysis and photovoltaics to photo-electrochemistry and sensors. Recently, the emergence of black TiO2 nanomaterial has triggered world-wide research interest, because of its substantially enhanced solar absorption and the improved photocatalytic activities. Here, a variety of synthetic strategies of black TiO2 are outlined, and the structural and chemical features, band structures and electronic properties of the black TiO2 nanomaterials are described in details, along with their photocatalytic performances as well as some other new applications.

Progress in Black Titania: A New Material for Advanced Photocatalysis

Pt-doped mesoporous Ti3+ self-doped TiO2 (Pt–Ti3+/TiO2) is in situ synthesized via an ionothermal route, by treating metallic Ti in an ionic liquid containing LiOAc, HOAc, and a H2PtCl6 aqueous solution under mild ionothermal conditions. Such Ti3+-enriched environment, as well as oxygen vacancies, is proven to be effective for allowing the in situ reduction of Pt4+ ions uniformly located in the framework of the TiO2 bulk. The photocatalytic H2 evolution of Pt–Ti3+/TiO2 is significantly higher than that of the photoreduced Pt loaded on the original TiO2 and commercial P25. Such greatly enhanced activity is due to the various valence states of Pt (Ptn+, n = 0, 2, or 3), forming Pt–O bonds embedded in the framework of TiO2 and ultrafine Pt metal nanoparticles on the surface of TiO2. Such Ptn+–O bonds could act as the bridges for facilitating the photogenerated electron transfer from the bulk to the surface of TiO2 with a higher electron carrier density (3.11 × 1020 cm–3), about 2.5 times that (1.25 × 1020 cm...

Pt-Enhanced Mesoporous Ti3+/TiO2 with Rapid Bulk to Surface Electron Transfer for Photocatalytic Hydrogen Evolution.

A black Ti3+-doped single-crystal TiO2 (Ti3+/TiO2) was one-pot synthesized by treating Ti metal in an ionic liquid containing LiAc and HAc under mild ionothermal conditions. The ionic liquid (1-methyl-imidazolium tetrafluoroborate) supplied an environment enriched with fluoride ions for dissolving titanium foil under ionothermal conditions, followed by reducing protons in acetic acid to form Ti3+ ions, leading to Ti3+-doped single-crystal TiO2 as a black powder. EPR and XPS results indicated the high concentrations of both Ti3+-dopants and oxygen vacancies. The Ti3+ incorporated into the TiO2 lattice could narrow the energy band gap of TiO2via forming intermediate energy levels, leading to a visible photocatalyst. Meanwhile, the oxygen vacancies could inhibit the photoelectron–hole recombination. As expected, such a black Ti3+/TiO2 exhibited high activity in the photocatalytic degradation of organic pollutants and water splitting for H2 production under irradiation with visible light and/or simulated solar light.

Fenghui Tian

Papers

Pt-Enhanced Mesoporous Ti3+/TiO2 with Rapid Bulk to Surface Electron Transfer for Photocatalytic Hydrogen Evolution.

Ionothermal synthesis of black Ti3+-doped single-crystal TiO2 as an active photocatalyst for pollutant degradation and H2 generation

Surface modulation of MoS2/O-ZnIn2S4 to boost photocatalytic H2 evolution

Oriented adsorption and efficient sensing of NO2 on MoSe2 monolayer: a comparative study with WSe2 monolayer