Photocatalysis principle

All the applications of photocatalysis have one common point they can help in obtaining processes that obey the requirements of green chemistry. In fact, many of the principles of sustainable chemistry are applied to photoinduced transformations in all areas of application [18]. The major achievement of photocatalysis is the use of catalysis and light, which are two of the pillars of sustainable chemistry. 

Heterogeneous particle morphology, in polymer colloids, 20 387 Heterogeneous photocatalysis, 19 73, 103 principles of, 29 74-75 Heterogeneous polymer blends, 20 343. 

The basic principle of semiconductor photocatalysis involves photogenerated electrons and holes migrating to the surface. (From Wang et ah, 2006)... 

Serpone N, Pelizzetti E (1989) Photocatalysis Fundamentals and Applications, Wiley, New York Schiavello M, Dordrecht H (1985) Photoelectrochemistiy, Photocatalysis, and Photoreactors Fundamentals and Developments Kluwer Academic, Boston, MA Linsebigler AL, Lu G, Yates JT (1995) Photocatalysis on Ti02 surfaces principles, mechanisms, and selected results. Chem Rev 95 735-758... 

From the abovedescribed principle of heterogeneous photocatalysis, it follows that photocatalytic reaction rates depend upon the characteristics of the irradiation, the mass of the photocatalyst, and the concentration (or partial pressure) of the reactants. 

Linsebigler AL, Lu G, Yates JT. Photocatalysis on Ti02 surfaces principles, mechanisms, and selected results. Chem Rev 1995 95 735-758. 

However, due to the inherent complexity of this minute photoelectro-chemical system, details of the underlying reaction mechanisms of photocatalysis are even today still far from being understood. In contrast to an ordinary photoelectrochemical cell which employs an external bias voltage to deliberately separate oxidation and reduction processes in different compartments of the reactor, in photocatalysis both processes occur on the surface of the same semiconductor particle, usually only separated by a distance of a few angstroms. Moreover, as is evident from basic principles, the reaction rate of the overall process will be limited by the... 

Sviridov, Dmitry V. he obtained his Ph.D. (1987) and D.Sc. (1999) degrees in Physical Chemistry from Belarussian State University (BSU). He currently holds an appointment of Professor of Chemistry at BSU and Principle Investigator in the Institute for Physico-Chemical Problems, BSU, Minsk, Belarus Republic. His scientific interests include photoelectrochemistry of semiconductors and molecular aggregates, electrocatalysis and environmental photocatalysis. E-mail ... 

In a single-crystal semiconductor (n-type) based photoelectrochemical cell, the problem of achieving charge separation is easily overcome by applying an anodic bias as was first demonstrated by Honda and Fujishima [263]. Using a single crystal Ti02, they were able to carry out the photoelectrolysis of water under the influence of an anodic bias. This concept to manipulate the photocatalytic reaction by electrochemical method can be extended to nanostructured semiconductor thin films [39,116]. The principle of electrochemically assisted photocatalysis is illustrated in Fig. 10. 

In an earlier review of the applications of photoluminescence (PL) techniques to the characterization of adsorption, catalysis, and photocatalysis (Anpo and Che, 1999), we addressed the basic principles of PL and the importance of PL measurements for understanding of (photo)catalytic processes. This chapter describes more recent developments and focuses on investigations of catalysts in the working state, with an emphasis on the role of local structure on photocatalytic reactions determined with PL and related techniques. 

The preceding review of PL which appeared in this series (Anpo and Che, 1999) gave the principles and applications of this technique to the investigation of solid surfaces in relation to adsorption, catalysis, and photocatalysis. 

Wang, C.Y., R. Pagel, J.K. Dohrmann and D.W. Bahnemann (2006a). Antenna mechanism and deaggregation concept Novel mechanistic principles for photocatalysis. Comptes Rendus Chimie, 9(5-6), 761-773. 

In summary, the present issue of Advances in Chemical Engineering Volume 36 offers an up-to-date overview and discussion of principles and applications of photo catalytic reaction engineering. Altogether, Volume 36 is an invitation to reflect on the possibilities of photocatalysis as a promising technology for green reaction engineering. 

More recently, the various aspects of light-responsive and photoreactive inorganic compounds in biological and bioinspired systems have been addressed (3-6). In the present contribution, some fundamental principles and first advances of the rapidly evolving fields of bioinorganic photochemistry and biomimetic photocatalysis will be discussed. No attempt will be made to provide a comprehensive coverage of the relevant literature, which is widespread across a bunch of different disciplines... 

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. 

The principle of photocatalysis is often explained with an illustration like Fig. 2, a schematic representation of the electronic structures of semiconducting materials, a band model. An electron in an electron-filled valence band (VB) is excited by photoirradiation to a vacant conduction band (CB), which is separated by a forbidden band, a band gap, from the VB, leaving a positive hole in the VB (Section III.B). These electrons and positive holes drive reduction and oxidation, respectively, of compounds adsorbed on the surface of a photocatalyst. Such an interpretation accounts for the photocatalytic reactions of semiconducting and insulating materials absorbing photons by the bulk of materials. In the definition of photocatalysis given above, however, no such limitation based on the electronic structure of a photocatalyst is included. For example, isolated... 

The ability to use fundamental design principles based upon modern experimental and theoretical techniques coupled with the ever-increasing cost of, and demand for energy, means semiconductor photocatalysis is a rich area for both scientific and technological development in the twenty-first century. 

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