Oxygen on metals

Wagner was first to propose the use of solid electrolytes to measure in situ the thermodynamic activity of oxygen on metal catalysts.17 This led to the technique of solid electrolyte potentiometry.18 Huggins, Mason and Giir were the first to use solid electrolyte cells to carry out electrocatalytic reactions such as NO decomposition.19,20 The use of solid electrolyte cells for chemical cogeneration , that is, for the simultaneous production of electrical power and industrial chemicals, was first demonstrated in 1980.21 The first non-Faradaic enhancement in heterogeneous catalysis was reported in 1981 for the case of ethylene epoxidation on Ag electrodes,2 3 but it was only... 

The effect of alkali presence on the adsorption of oxygen on metal surfaces has been extensively studied in the literature, as alkali promoters are used in catalytic reactions of technological interest where oxygen participates either directly as a reactant (e.g. ethylene epoxidation on silver) or as an intermediate (e.g. NO+CO reaction in automotive exhaust catalytic converters). A large number of model studies has addressed the oxygen interaction with alkali modified single crystal surfaces of Ag, Cu, Pt, Pd, Ni, Ru, Fe, Mo, W and Au.6... 

Alt H, Binder H, Sandstete G (1973) Mechanism of the electrocatalytic reduction of oxygen on metal chelates. J Catal 28 8-19... 

Rao, C.N.R., Kamath, P.V. andYashonath, S. (1982) Molecularly adsorbed oxygen on metals electron spectroscopic studies. Chemical Physics Letters, 88, 13—16. 

The influence of oxygen on metal surfaces, obtained by scraping solid metal pieces in vacuo (l0 mm. Hg), was investigated by Fianda and Lange (59). After scraping, for all metals (Ag, Cu, Sn, Zn, Cd, Pb, Al,... 

Propane Selective Oxidation to Propene and Oxygenates on Metal Oxides. In Metal Oxides, Chemistry and Applications (ed. J.LG. Eierro), CRC Press, Boca Raton, p. 414. 

Frantz P, Didziulis SV (1998) Detailed spectroscopic studies of oxygen on metal carbide surfaces. Surf Sci 412/413 384... 

Scheme 1 Products of the activation of molecular oxygen on metals. ...

Doomkamp C, Clement M, Ponec V (1999) The isotopic exchange reaction of oxygen on metal oxides. J Catalysis 182 390-399... 

Katz G, Zeiri Y and Kosloff R 1999 Non-adiabatic charge transfer process of oxygen on metal surfaces Surf. Sci. 425 1... 

The chemisorption of oxygen on metal surfaces—or of oxide films on metal surfaces—is one of the first steps of (further) oxidation of the metal. It is likely that the first step of this chemisorption process consists of a molecular chemisorption. 

However, a different definition was used for [426]. This agrees well with the fact that the chemisorption of oxygen on metals usually takes place with only small activation energy [423,427]. The temperature dependence also supports this fact. A decrease of the reaction was observed with increasing temperature of the substrate surface. Ritter [293,298] explains this observation with a reduction of the condensation coefficient a of oxygen. 

The catalytic oxidation of carbon monoxide by oxygen on metallic oxide, is a typical example. 

Because the free energy of adsorption per mole of oxygen decreases with amount of oxygen adsorbed (the O-substrate bond becomes weaker), multilayer adsorbed oxygen on metal M eventually favors transformation to a crystalline stoichiometric oxide. In other words, AG for O-Mads + n02 (n02)-0-Mads... 

In recent years many studies on the reaction between hydrogen and oxygen on metal surfaces have been reported. Although this reaction is expected to be one of the simplest oxidation reactions, rather complex phenomena are observed which make a determination of the reaction mechanism difficult. Even for the water formation reaction on Pt(111), the system which has been most widely studied, an understanding of the reaction process seems only just emerging [5]. 

Beziat, J., Besson, M. and GaUezot, P. (1996). Liquid Phase Oxidation of Cyclohexanol to Adipic Acid with Molecular Oxygen on Metal Catalysts, Appl. Catal. A Gen., 135, L7—LI 1. Abbadi, A. and vanBekkum, H. (1996). Selective Chemo-Catalytic Routes for the Preparation of Beta-Hydroxypyruvic Acid, A/7/ Z. Catal. A Gen., 148, pp. 113-122. 

Figure 3-21. Passivity promoters and dissolution moderators according to the heat of adsorption of oxygen on metals [A/f ds (oxygen)] taken at low surface coverage, and the surface metal-metal bond strength ( m-m) (evaluated from the heat of sublimation and the coordination number of the metal) (Marcus, 1994, 1998).

Propane Selective Oxidation to Propene and Oxygenates on Metal Oxides 415... 

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