Vapor-phase hydrothermal synthesis of rutile TiO2 nanostructured film with exposed pyramid-shaped (1 1 1) surface and superiorly photoelectrocatalytic performance

An overview on non-spherical semiconductors for heterogeneous photocatalytic degradation of organic water contaminants

Because of their carcinogenicity and mutagenicity, the elimination of organic contaminants from surface and subsurface water is a subject of environmental significance. Conventional water decontamination approaches such as membrane separation, ultrafiltration, adsorption, reverse osmosis, coagulation, etc., have relatively higher operating costs and can generate highly toxic secondary contaminants. On the other hand, heterogeneous photocatalysis, an advanced oxidation process (AOP), is considered a clean and cost-effective process for organic pollutants degradation. Owing to their distinctive structure and physicochemical properties non-spherical semiconductors have gained considerable limelight in the photocatalytic degradation of organic contaminants. The current review briefly introduces a wide range of organic water contaminants. Recent advances in non-spherical semiconductor assembly and their photocatalytic degradation applications are highlighted. The underlying mechanism, fundamentals of photocatalytic reactions, and the factors affecting the degradation performance are also alluded including the current challenges and future research perspectives.

Catalytic decontamination of organic/inorganic pollutants in water and green H2 generation using nanoporous SnS2 micro-flower structured film

Recycling water and generation of H₂ simultaneously as a green technology can be a key attraction in establishing environmental sustainability. Towards this endeavor, nanoporous SnS₂ film electrodes deposited by a solution process on nickel foam demonstrate a promising electrocatalytic activity towards generation of H₂ gas at cathode while the anodic reaction leads to the decomposition of urea-waste at the rate of 10 mA cm^-2 in 1 M KOH with a lower cell-potential of 1.38 V vs RHE. The SnS₂ electrode also demonstrates an excellent catalytic activity towards hydrogen evolution reaction in a wide pH range (0-14). In addition, the SnS₂ film deposited on an FTO-substrate shows 97.56% photocatalytic-degradation of methylene-blue dye within 180 min under irradiation of visible light with a good recyclability of the photocatalyst, suggesting its high potentiality for the practical application. The demonstrated good electro- and photo-catalytic activities can be ascribed to the nanoporous structure of SnS₂ film in a flower like 3D-fashion, offering availability of abundant active catalytic sites. Our results demonstrate the application of SnS₂ nanoporous film as catalyst can be a significant greenery path for the removal of harmful inorganic/organic hazardous wastes from waste-water with simultaneous generation of green H₂ fuel.

Crystal Facet Engineering of Photoelectrodes for Photoelectrochemical Water Splitting

Photoelectrochemical (PEC) water splitting is a promising approach for solar-driven hydrogen production with zero emissions, and it has been intensively studied over the past decades. However, the solar-to-hydrogen (STH) efficiencies of the current PEC systems are still far from the 10% target needed for practical application. The development of efficient photoelectrodes in PEC systems holds the key to achieving high STH efficiencies. In recent years, crystal facet engineering has emerged as an important strategy in designing efficient photoelectrodes for PEC water splitting, which has yet to be comprehensively reviewed and is the main focus of this article. After the Introduction, the second section of this review concisely introduces the mechanisms of crystal facet engineering. The subsequent section provides a snapshot of the unique facet-dependent properties of some semiconductor crystals including surface electronic structures, redox reaction sites, surface built-in electric fields, molecular adsorption, photoreaction activity, photocorrosion resistance, and electrical conductivity. Then, the methods for fabricating photoelectrodes with faceted semiconductor crystals are reviewed, with a focus on the preparation processes. In addition, the notable advantages of the crystal facet engineering of photoelectrodes in terms of light harvesting, charge separation and transfer, and surface reactions are critically discussed. This is followed by a systematic overview of the modification strategies of faceted photoelectrodes to further enhance the PEC performance. The last section summarizes the major challenges and some invigorating perspectives for future research on crystal facet engineered photoelectrodes, which are believed to play a vital role in promoting the development of this important research field.

The design of new magnetic-photocatalyst nanocomposites (CoFe2O4–TiO2) as smart nanomaterials for recyclable-photocatalysis applications

Magnetically recyclable 3D CoFe₂O₄–TiO₂photocatalyst nanocomposite.

Theoretical investigation on the adsorption configuration and (•)OH-initiated photocatalytic degradation mechanism of typical atmospheric VOCs styrene onto (TiO2)n clusters

In this study, the adsorption mechanism and hydroxyl radical (^•OH)-initiated photocatalytic degradation mechanism of styrene onto different (TiO₂)_n clusters were investigated using density functional theory. Styrene, a typical model atmospheric volatile organic compound (VOC), was found to be readily adsorbed onto (TiO₂)_n clusters through its vinyl group with strong chemisorption. This suggests that (TiO₂)_n clusters (sub 1 nm) are able to effectively adsorb and trap styrene. Adsorbed styrene is then easily attacked by ^•OH to form a series of vinyl-OH-adducts. Conversely, phenyl-OH-adducts and H-abstraction products are very difficult to form in this system. Kinetics calculations using canonical variational transition state theory show that temperature has little effect on the rate constants during photocatalytic degradation process. The presence of TiO₂ does not change the degradation mechanism of styrene, but can accelerate its photocatalyic degradation rate, and the rate will increase as TiO₂ cluster size increases; as such, the TiO₂ nano-clusters catalyst should have the photocatalytic ability to effectively degrade styrene. This theory-based study offers insights into the catalytic effect of TiO₂ catalyst and the photocatalytic degradation mechanism of benzene series air pollutants at the molecular level.