Catalysis electron theory

Haber, J. and Witko, M. Oxidation catalysis — Electronic theory revisited. J. Catal. 2003, 216, 416. 

The mechanism of the poisoning effect of nickel or palladium (and other metal) hydrides may be explained, generally, in terms of the electronic theory of catalysis on transition metals. Hydrogen when forming a hydride phase fills the empty energy levels in the nickel or palladium (or alloys) d band with its Is electron. In consequence the initially d transition metal transforms into an s-p metal and loses its great ability to chemisorb and properly activate catalytically the reactants involved. 

Herman Pines and Luke A. Schaap The Use of X-Ray K-Absorption Edges in the Study of Catalytically Active Solids Robert A. Van Nordstrand The Electron Theory of Catalysis on Semiconductors Th. Wolkenstein... 

The notions of the electronic theory of catalysis developed in the 1950s by... 

A clue to the understanding of the photocatalytic effect is the electronic theory of catalysis on semiconductors (1). As will be seen later, the existence and the basic regularities of the photocatalytic effect follow directly from the electronic theory of catalysis. Whereas the theory of the photoadsorp-tive effect (the influence of illumination on the adsorption capacity of a semiconductor) has received much attention in the literature, the theory of the photocatalytic effect based on the electronic theory of catalysis has almost escaped the attention of investigators. The purpose of the present work is to fill in the gap to a certain extent. We shall naturally start by recalling certain principal concepts of the electronic theory which will be needed later. 

The photoadsorption effect as such does not constitute the subject matter of the present article. We shall consider it very briefly, only to the extent necessary to allow one to draw analogies between the mechanisms of the photoadsorptive and photocatalytic effects. The photoadsorptive effect has been studied sufficiently well. A brief summary of the experimental data will be given below. The mechanism of the phenomenon has been thoroughly discussed in a number of theoretical works from the standpoint of the electronic theory of chemisorption and catalysis C3,4,6-8). 

We shall consider the hydrogen-deuterium exchange reaction from the viewpoint of the electronic theory of chemisorption and catalysis (27),... 

Reaction (70) in the dark has been discussed in the literature (1) from the viewpoint of the electronic theory of catalysis. The photoreaction (70) has also been considered in the literature (8), though briefly and purely qualitatively. In the present article we shall proceed from the mechanism which has been discussed in the literature (1) as one of the possible mechanisms. Let us examine the influence of illumination on the rate of the reaction [see reference (47) ]. 

Wolkenstein, Th. Theorie electronique de la catalyse sur les semiconducteurs. Masson et Cie, Paris, 1961 F. F. Vol kenshtein (Th. Wolkenstein), The Electronic Theory of Catalysis on Semiconductors. Pergamon, Oxford, 1963 Th. Wolkenstein, Elektronentheorie der Katalyse an Halbleitern. VEB Deutscher Verlag der Wissenschaften, Berlin, 1964. 

Robert A. Van Nordstrand The Electron Theory of Catalysis on Semiconductors Th. Wolkenstein... 

Raimes, S. (1972), Many-Electron Theory, North Holland, Amsterdam. Ruckenstein, E. and Huang, Y.S. (1973), J. Catalysis 30, 309. 

Yang, W. and R. G. Parr. 1985. Hardness, softness and the Fukui function in the electronic theory of metals and catalysis. Proc. Natl. Acad. Sci. USA 82 6723-6726. 

This article presents a concise account of the present state of the electron theory of catalysis on semiconductors. It aims to describe the main outlines of the electron theory primarily as it has been developed in the past ten years by the author and co-workers. It also contains a short summary of the results of a number of experimental works dealing with electronic phe-... 

The electron theory of catalysis cannot as yet be regarded as a complete theory. It resembles a building from which the scaffolding has not yet been removed. It is being erected on the foundation of the modern theory of the solid state and thus introduces new concepts and ideas into the theory of catalysis. This does not mean, of course, that it excludes other concepts and ideas prevalent today in other theories of catalysis. On the contrary, it makes use of these while attempting to disclose their physical content. 

The electron theory of catalysis and other, mainly phenomenological, theories of catalysis are not as a rule mutually exclusive. They deal with different aspects of catalysis and thus differ from one another mainly in their approach to the problem. The electron theory is interested in the elementary (electronic) mechanism of the phenomenon and approaches the problems of catalysis from this point of view. 

The existing phenomenological theories of catalysis bear approximately the same relation to the electron theory as the theory of the chemical bond, which was prevalent in the last century and which made use of valence signs (and dealt only with these signs), bears to the modern quantum-mechanical theory of the chemical bond which has given the old valence signs physical content, thereby disclosing the physical nature of the chemical forces. 

The father of the electron theory of catalysis is L. V. Pisarzhevsky (Kiev). His work, begun in 1916, formed part of an extensive series of investigations dealing with electronic phenomena in chemistry. L. V. Pisarzhevsky was the first to attempt to relate the catalytic properties of solids to... 

At present (beginning from 1948) the electron theory is being developed on a modern, more advanced theoretical basis. In the U.S.S.R. the initiator of this new electronic quantum-mechanical trend in catalysis is S. Z. Roginsky (Moscow), from whose laboratory a whole series of experimental and theoretical works has issued. Electronic phenomena in catalysis are also dealt with in a number of papers by A. N. Terenin and his school (Leningrad), V. I. Lyashenko and co-workers (Kiev), S. Y. Pshezhetsky and I. A. Myasnikov (Moscow), and others. 

In its present stage of development, the electron theory of catalysis deals with catalysts which by their electrical properties belong to the class of semiconductors. Catalysis on semiconductors, as is well known, is extremely widespread, far more so than might appear at first sight. This is due to the circumstance that in most cases a metal is enclosed in a semiconducting coat and the processes which apparently take place on the surface of the metal actually take place on the surface of this semiconducting coat, whereas the underlying metal frequently takes practically no part in the process. 

The results of the electron theory as developed for semiconductors are fully applicable to dielectrics. They cannot, however, be automatically applied to metals. Contrary to the case of semiconductors, the application of the band theory of solids to metals cannot be considered as theoretically well justified as the present time. This is especially true for the transition metals and for chemical processes on metal surfaces. The theory of chemisorption and catalysis on metals (as well as the electron theory of metals in general) must be based essentially on the many-electron approach. However, these problems have not been treated in any detail as yet. 

The phenomenon of catalyst modification by impurities (promoting by poisons, poisoning by promoters) was discovered in 1940 in the laboratory of S. Z. Roginsky. A summary of the experimental data is given in (74, 5). A theoretical interpretation of the phenomenon was given in the first papers on the electron theory of catalysis (1, 37, 66, 47)- The effect of impurities on the activity of a catalyst may be regarded as the fourth consequence of the theory. 

See for instance VoT Kenshtein, F.F. (1953) The Electronic Theory of Catalysis on Semiconductors, Macmillan, New York. 

---