[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

The production of hydrogen from water using a catalyst and solar energy is an ideal future energy source, independent of fossil reserves. For an economical use of water and solar energy, catalysts that are sufficiently efficient, stable, inexpensive and capable of harvesting light are required. Here, we show that an abundant material, polymeric carbon nitride, can produce hydrogen from water under visible-light irradiation in the presence of a sacrificial donor. Contrary to other conducting polymer semiconductors, carbon nitride is chemically and thermally stable and does not rely on complicated device manufacturing. The results represent an important first step towards photosynthesis in general where artificial conjugated polymer semiconductors can be used as energy transducers.

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A metal-free polymeric photocatalyst for hydrogen production from water under visible light

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)

Heterogeneous photocatalyst materials for water splitting

Energy harvested directly from sunlight offers a desirable approach toward fulfilling, with minimal environmental impact, the need for clean energy. Solar energy is a decentralized and inexhaustible natural resource, with the magnitude of the available solar power striking the earth’s surface at any one instant equal to 130 million 500 MW power plants.1 However, several important goals need to be met to fully utilize solar energy for the global energy demand. First, the means for solar energy conversion, storage, and distribution should be environmentally benign, i.e. protecting ecosystems instead of steadily weakening them. The next important goal is to provide a stable, constant energy flux. Due to the daily and seasonal variability in renewable energy sources such as sunlight, energy harvested from the sun needs to be efficiently converted into chemical fuel that can be stored, transported, and used upon demand. The biggest challenge is whether or not these goals can be met in a costeffective way on the terawatt scale.2

http://pubs.acs.org/doi/pdf/10.1021/cr1002326

Solar Water Splitting Cells

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

Overall water splitting using a semiconductor photocatalyst with sunlight has long been viewed as a potential means of large-scale H2 production from renewable resources. In general, the reaction c...

Development of Novel Photocatalyst and Cocatalyst Materials for Water Splitting under Visible Light

A two-step photocatalytic water splitting (Z-scheme) system consisting of a modified BaZrO3–BaTaO2N solid solution, a paired photocatalyst, and a reversible donor/acceptor pair (i.e., redox mediator) was constructed. BaZrO3–BaTaO2N (Zr/Ta = 0.05) having a band gap of 1.8 eV has sufficient potential to reduce and oxidize water by absorbing visible photons of up to 660 nm. Upon suitable modification of this material with nanoparticulate cocatalysts, both H2 and O2 were evolved individually in the presence of reversible redox couples (viz., IO3–/I– and Fe3+/Fe2+), although O2 evolution from aqueous solution containing Fe3+ was negligible. Among various combinations tested, BaZrO3–BaTaO2N modified with Pt nanoparticles was the most suitable for H2 evolution in the presence of an IO3–/I– pair, achieving Z-scheme water splitting into H2 and O2 in combination with either PtOx/WO3 or TiO2 rutile as an O2 evolution photocatalyst even under simulated sunlight.

Solar-Driven Z-scheme Water Splitting Using Modified BaZrO3–BaTaO2N Solid Solutions as Photocatalysts

Ta3N5 photoanodes for water splitting prepared by sputtering

Aspects of the water splitting mechanism on (Ga1−xZnx)(N1−xOx) photocatalyst powder are discussed on the basis of the effects of cocatalyst loading, light intensity, hydrogen/deuterium isotopes, and reaction temperature on photocatalytic activity. The loading amount of Rh2−yCryO3 cocatalyst significantly affected the photocatalytic behavior with varying light intensity. When the loading amount of Rh2−yCryO3 as a H2 evolution cocatalyst was insufficient, the reaction order for light intensity was lower than unity. This is because photoexcited electrons accumulated in the photocatalyst and recombined with photoexcited holes more frequently than they contributed to the water splitting reaction. When a sufficient amount of cocatalyst was loaded, on the other hand, accumulation of photoexcited electrons was suppressed and the water splitting rate increased monotonically with light intensity. At a light intensity equivalent to solar irradiation, AM1.5, the water splitting rate using modified (Ga1−xZnx)(N1−xOx) ...

Aspects of the Water Splitting Mechanism on (Ga1−xZnx)(N1−xOx) Photocatalyst Modified with Rh2−yCryO3 Cocatalyst

Water splitting using a semiconductor photocatalyst with sunlight has long been viewed as a potential means of large-scale H2 production from renewable resources. Different from anatase TiO2 , rutile enables preferential water oxidation, which is useful for the construction of a Z-scheme water-splitting system. The combination of rutile TiO2 with a suitable H2 -evolution photocatalyst such as a Pt-loaded BaZrO3 -BaTaO2 N solid solution enables solar-driven water splitting into H2 and O2 . While rutile TiO2 is a wide-gap semiconductor with a bandgap of 3.0 eV, co-doping of rutile TiO2 with certain metal ions and/or nitrogen produces visible-light-driven photocatalysts, which are also useful as a component for water oxidation in visible-light-driven Z-scheme water splitting. The key to achieving highly efficient water oxidation is to maintain a charge balance of dopants in the rutile, because single doping typically produces trap states that capture photogenerated electrons and/or holes. Here we provide a concise summary of rutile TiO2 -based photocatalysts for water-splitting systems.

Kazuhiko Maeda

Papers

Development of Novel Photocatalyst and Cocatalyst Materials for Water Splitting under Visible Light

Solar-Driven Z-scheme Water Splitting Using Modified BaZrO3–BaTaO2N Solid Solutions as Photocatalysts

Ta3N5 photoanodes for water splitting prepared by sputtering

Aspects of the Water Splitting Mechanism on (Ga1−xZnx)(N1−xOx) Photocatalyst Modified with Rh2−yCryO3 Cocatalyst

Water Splitting on Rutile TiO2 -Based Photocatalysts.