Recent Progress in Two-Dimensional Oxide Photocatalysts for Water Splitting.
14 Jul 2014-Journal of Physical Chemistry Letters (American Chemical Society)-Vol. 5, Iss: 15, pp 2533-2542
TL;DR: In this system, a certain type of 2D oxide nanosheet shows high activity without co-catalyst loading and the driving force of the carrier transfer to the reaction sites was found to be the potential gradient generated by the Nanosheet junction.
Abstract: This Perspective focuses on the photocatalytic activity of two-dimensional (2D) oxide and nitrogen-doped oxide crystals and the effective use of 2D photocatalysts for understanding the mechanism of the water splitting reaction. Strategies for improving the activities of 2D photocatalysts are slightly different from those of bulk photocatalysts. Although it is well-known that a photocatalyst without co-catalyst loading has low activity for hydrogen production from water, a certain type of 2D oxide nanosheet shows high activity without co-catalyst loading. It is difficult to determine what factors contribute to this separation of oxidation and reduction sites of water because there are many factors on the reaction surface. A nanosheet p-n junction surface is an ideal surface for understanding the carrier transfer during the photocatalytic reaction. In this system, the driving force of the carrier transfer to the reaction sites was found to be the potential gradient generated by the nanosheet junction.
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TL;DR: In this paper, the authors describe the barrier, progress and future direction of research on the correlation of the chemical constituent, size, dimensionality, architecture, crystal structure, microstructure and electronic band structure of photocatalysts (or photoelectrodes) with five vital processes including light absorption, charge separation, migration and recombination as well as surface redox reactions.
803 citations
TL;DR: Recently, due to the attractive properties such as appropriate band structure, ultrahigh specific surface area, and more exposed active sites, two-dimensional (2D) photocatalysts have attracted significant attention as discussed by the authors.
Abstract: Hydrogen generation from the direct splitting of water by photocatalysis is regarded as a promising and renewable solution for the energy crisis The key to realize this reaction is to find an efficient and robust photocatalyst that ideally makes use of the energy from sunlight Recently, due to the attractive properties such as appropriate band structure, ultrahigh specific surface area, and more exposed active sites, two-dimensional (2D) photocatalysts have attracted significant attention for photocatalytic water splitting This Review attempts to summarize recent progress in the fabrication and applications of 2D photocatalysts including graphene-based photocatalysts, 2D oxides, 2D chalcogenides, 2D carbon nitride, and some other emerging 2D materials for water splitting The construction strategies and characterization techniques for 2D/2D photocatalysts are summarized Particular attention has been paid to the role of 2D/2D interfaces in these 2D photocatalysts as the interfaces and heterojunctions a
717 citations
TL;DR: Recent progress on the emerging strategies for tailoring 2D material-based photocatalysts to improve their photo-activity including elemental doping, heterostructure design and functional architecture assembly is discussed.
Abstract: Two-dimensional (2D) materials have attracted increasing attention for photocatalytic applications because of their unique thickness dependent physical and chemical properties. This review gives a brief overview of the recent developments concerning the chemical synthesis and structural design of 2D materials at the nanoscale and their applications in photocatalytic areas. In particular, recent progress on the emerging strategies for tailoring 2D material-based photocatalysts to improve their photo-activity including elemental doping, heterostructure design and functional architecture assembly is discussed.
620 citations
TL;DR: In this critical review, the recent progress and advances of COF photocatalysts are thoroughly presented and diverse linkers between COF building blocks such as boron- containing connections and nitrogen-containing connections are summarised and compared.
Abstract: In the light of increasing energy demand and environmental pollution, it is urgently required to find a clean and renewable energy source. In these years, photocatalysis that uses solar energy for either fuel production, such as hydrogen evolution and hydrocarbon production, or environmental pollutant degradation, has shown great potential to achieve this goal. Among the various photocatalysts, covalent organic frameworks (COFs) are very attractive due to their excellent structural regularity, robust framework, inherent porosity and good activity. Thus, many studies have been carried out to investigate the photocatalytic performance of COFs and COF-based photocatalysts. In this critical review, the recent progress and advances of COF photocatalysts are thoroughly presented. Furthermore, diverse linkers between COF building blocks such as boron-containing connections and nitrogen-containing connections are summarised and compared. The morphologies of COFs and several commonly used strategies pertaining to photocatalytic activity are also discussed. Following this, the applications of COF-based photocatalysts are detailed including photocatalytic hydrogen evolution, CO2 conversion and degradation of environmental contaminants. Finally, a summary and perspective on the opportunities and challenges for the future development of COF and COF-based photocatalysts are given.
481 citations
TL;DR: The combination of different strategies, i.e., 2D-structure construction, the introduction of surface oxygen vacancies, and the creation of localized surface plasmon resonance can promote the light-harvesting performance of tungsten oxide through accumulative and synergistic effects.
Abstract: Substoichiometric tungsten oxide single-crystal nanosheets are successfully prepared via the exfoliation of layered tungstic acid and subsequent introduction of oxygen vacancies. The combination of different strategies, i.e., 2D-structure construction, the introduction of surface oxygen vacancies, and the creation of localized surface plasmon resonance can promote the light-harvesting performance of tungsten oxide through accumulative and synergistic effects.
436 citations
References
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TL;DR: Film and powders of TiO2-x Nx have revealed an improvement over titanium dioxide (TiO2) under visible light in optical absorption and photocatalytic activity such as photodegradations of methylene blue and gaseous acetaldehyde and hydrophilicity of the film surface.
Abstract: To use solar irradiation or interior lighting efficiently, we sought a photocatalyst with high reactivity under visible light. Films and powders of TiO 2- x N x have revealed an improvement over titanium dioxide (TiO 2 ) under visible light (wavelength 2 has proven to be indispensable for band-gap narrowing and photocatalytic activity, as assessed by first-principles calculations and x-ray photoemission spectroscopy.
11,402 citations
TL;DR: This critical review shows the basis of photocatalytic water splitting and experimental points, and surveys heterogeneous photocatalyst materials for water splitting into H2 and O2, and H2 or O2 evolution from an aqueous solution containing a sacrificial reagent.
Abstract: This critical review shows the basis of photocatalytic water splitting and experimental points, and surveys heterogeneous photocatalyst materials for water splitting into H2 and O2, and H2 or O2 evolution from an aqueous solution containing a sacrificial reagent Many oxides consisting of metal cations with d0 and d10 configurations, metal (oxy)sulfide and metal (oxy)nitride photocatalysts have been reported, especially during the latest decade The fruitful photocatalyst library gives important information on factors affecting photocatalytic performances and design of new materials Photocatalytic water splitting and H2 evolution using abundant compounds as electron donors are expected to contribute to construction of a clean and simple system for solar hydrogen production, and a solution of global energy and environmental issues in the future (361 references)
8,850 citations
TL;DR: The findings suggest that the use of solar energy for photocatalytic water splitting might provide a viable source for ‘clean’ hydrogen fuel, once the catalytic efficiency of the semiconductor system has been improved by increasing its surface area and suitable modifications of the surface sites.
Abstract: The photocatalytic splitting of water into hydrogen and oxygen using solar energy is a potentially clean and renewable source for hydrogen fuel. The first photocatalysts suitable for water splitting, or for activating hydrogen production from carbohydrate compounds made by plants from water and carbon dioxide, were developed several decades ago. But these catalysts operate with ultraviolet light, which accounts for only 4% of the incoming solar energy and thus renders the overall process impractical. For this reason, considerable efforts have been invested in developing photocatalysts capable of using the less energetic but more abundant visible light, which accounts for about 43% of the incoming solar energy. However, systems that are sufficiently stable and efficient for practical use have not yet been realized. Here we show that doping of indium-tantalum-oxide with nickel yields a series of photocatalysts, In(1-x)Ni(x)TaO(4) (x = 0-0.2), which induces direct splitting of water into stoichiometric amounts of oxygen and hydrogen under visible light irradiation with a quantum yield of about 0.66%. Our findings suggest that the use of solar energy for photocatalytic water splitting might provide a viable source for 'clean' hydrogen fuel, once the catalytic efficiency of the semiconductor system has been improved by increasing its surface area and suitable modifications of the surface sites.
2,931 citations
TL;DR: An advance in the catalysis of the overall splitting of water under visible light is described: the new catalyst is a solid solution of gallium and zinc nitrogen oxide, modified with nanoparticles of a mixed oxide of rhodium and chromium, which functions as a promising and efficient photocatalyst in promoting the evolution of hydrogen gas.
Abstract: Enhancing catalytic performance holds promise for hydrogen production by water splitting in sunlight.
2,537 citations
TL;DR: The photocatalytic methodology not only provides an on-demand UV-assisted reduction technique but also opens up new ways to obtain photoactive graphene-semiconductor composites.
Abstract: Graphene oxide suspended in ethanol undergoes reduction as it accepts electrons from UV-irradiated TiO2 suspensions. The reduction is accompanied by changes in the absorption of the graphene oxide, as the color of the suspension shifts from brown to black. The direct interaction between TiO2 particles and graphene sheets hinders the collapse of exfoliated sheets of graphene. Solid films cast on a borosilicate glass gap separated by gold-sputtered terminations show an order of magnitude decrease in lateral resistance following reduction with the TiO2 photocatalyst. The photocatalytic methodology not only provides an on-demand UV-assisted reduction technique but also opens up new ways to obtain photoactive graphene-semiconductor composites.
2,397 citations