Photocatalysts inorganic materials

The performance of semiconducting inorganic materials as a photocatalyst depends much on the physical properties of the particles such as crystallinity, size and morphology. The effect can be even more pronounced when using two or more materials together, since an intimate interaction between particles is more important in the multicomponent system (So et al., 2004). 

Certain inorganic materials can be employed as photocatalysts for the synthesis or degradation of compounds in heterogeneous systems. Relevant devices contain, for example, films incorporating immobilized photocatalyst particles. Typically, titania, Ti02, is used for the treatment of water contaminated with chemical pollutants and/or bacteria [9]. The contaminants are oxidized by reactive species, i.e. hydroxyl and superoxide radicals, generated by reaction of electron/hole pairs with O2 and water adsorbed at the particle surface. Electron/hole pairs are formed when UV light (>, <400 nm) is absorbed by titania (see Scheme 14.5). 

Fluorescent and photoluminescent nanofiUers, such as CdTe, CdSe, CdS nanoparticles or quantum dots (QDs), ZnS and ZnSe QDs, and complexes of trivalent europium ion (Eu ), are promising inorganic materials with photoelectric, thermoelectric, and photoluminescent properties that find applications in optoelectronic devices, optical sensors, as photocatalysts for organic pollutants remediation [39] or hydrogen production [40], and as fluorescent biomaterials [41]. 

Several sensitizers have been used, such as metal complexes (Ru, Re) with the 2N - 1 ligand and its derivatives or organic complex molecules. Solid inorganic materials (http //www2.lbl.gov/mfea/assets/docs/posters/14 Artificial Photosyn thesis) can also be used as heterogeneous photocatalysts. 

Krissanasaeranee, M., et al., Complex carbon nanotube-inorganic hybrid materials as next-generation photocatalysts. Chemical Physics Letters, 2010. 496(1-3) p. 133-138. 

Nakajima, T., Xu, Y.-H., Mori, Y. et al. (2005) Combined use of photocatalyst and adsorbent for the removal of inorganic arsenic(III) and organoarsenic compounds from aqueous media. Journal of Hazardous Materials, 120(1-3), 75-80. 

Refractory dust particles not only serve as condensation nuclei for ices (see above), but are also necessary for energy dissipation during gas phase reaction between energetic atoms and molecules. Furthermore, solid inorganic particles (mostly oxides and sulphides) may play a role of photocatalysts in transformations of organic materials in both space and the primitive soup [5, 31]. 

Semiconductor particles and films have been found to act as heterogeneous photocatalysts in a number of environmentally important reactions. Materials such as Ti02 and CdS have been found to be efficient in laboratory-scale pollution abatement systems, reducing both organic and inorganic pollutants/impurities to harmless species (see [1-35] and references therein). Photocatalysts have been shown to be useful for decomposition of O3 [36], destruction of bacteria [37-39] and viruses [40], purification of air [41], photosplitting of water [42,43] and clean-up of oil spills [44,45]. Photocat-... 

This review has been written in order to clarify fundamental aspects of photocatalysis, an important subject in inorganic and material chemistry, not to present a list of studies on photocatalysis reported so far, since it seems rather difficult to make a complete review by introducing all or a large part of the reported studies on photocatalysis of relatively long history. This review is based on the author s experience in studies on photocatalysis and topics are limited to so-called semiconductor photocatalysis definition and examples of photocatalysis, its principle and kinetics, visible light-induced photocatalysis, and design of active photocatalysts are discussed in detail. 

PHOTOCATALYSIS BY INORGANIC SOLID MATERIALS 421 VI. Design of Active Photocatalysts... 

K.G. Kanade, Jin-OoK Baeg, U.P. Mulik, D.P. Amalnerkar, B.B. Kale, Nano-CdS by polymer-inorganic solid-state reaction Visible light pristine photocatalyst for hydrogen generation , Materials Research Bulletin, 41, 2219-2225, (2006). 

In conclusion, over 130 semiconductors are known to catalyze the photochemical water-splitting reaction according to eq 1 or either water oxidation or reduction in the presence of sacrificial agents. Even though the principle activitycontrolling factors in semiconductor-heterostructures have been identified, many aspects of the function of inorganic photocatalysts are still unclear. Most importantly, the molecular mechanism of water reduction and oxidation on the semiconductor surface has not yet been elucidated in sufficient detail. ° Many questions about charge transfer between semiconductor and cocatalysts, and its dependence on the structural and electronic features of the interface are still open. The effect of variable material preparations and surface impurities on the catalytic activity of semiconductors (e.g. sulfur and oxide on... 

In general, photocatalytic membranes could be divided into polymeric and inorganic ones. The photocatalyst could be supported on a membrane surface or entrapped in a membrane structure. The method of photocatalyst incorporation in the membrane structure depends mainly on the membrane material. In Fig. 6.17 a simplified division of photocatalytic membranes with reference to the appUcation, membrane material and preparation method is shown. 

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