Oxygen evolution reaction surface oxidation model

The first step was the evolution away from the Schottky barrier model of photoelectrochemistry caused by the evidence from the late 1970s onward that the rate of photoelectrochemical reactions was heavily dependent on surface effects (Uosaki, 1981 Szklarczyk, 1983). This was followed by the use of both a photocathode and a photoanode in the same cell (Ohashi, 1977). Then the use of nonactive thin protective passive layers of oxides and sulfides allowed photoanodes to operate in potential regions in which they would otherwise have dissolved (Bockris and Uosaki, 1977). The final step was the introduction of electrocatalysis of both hydrogen and oxygen evolution by means of metal islets of appropriate catalytic power (Bockris and Szklarczyk, 1983). 

In order to interpret these observations, a The surface redox couple MO/M can comprehensive model for anodic oxidation act as a mediator in the oxidation of of organics in acidic media, including organics at active electrodes (Eq. 79). competition with oxygen evolution, has This reaction competes with the side been proposed [170]. This model permits reaction of oxygen evolution due to the... 

Many reactions of industrial importance are electrocatalytic, i.e., they involve the specific adsorption of intermediates, for example hydrogen, chlorine, and oxygen evolution, oxygen reduction, and methanol or ethanol oxidation in fuel cells. Many different electrochemical techniques were used to study these reactions, and EIS is one of them, providing interesting kinetic and surface information. Certain model reactions will be presented in what follows with a detailed method of relating impedance parameters with mechanistic and kinetic equations. 

Figure 1 A Model of the surface crystallography of iron oxide (Fe20s) as determined from LEED analysis of a thin fdm grown at Imbar oxygen pressure. The numbers indicate the positional changes of the atomic layers in percent with respect to the position in the bulk structure. B LEED image of a film before and after use as catalyst of dehydrogenation of ethylbenzene (EB) to styrene reaction temperature 873 K, reactant pressure Ibar, composition steam to EB 10 1, LHSV 0.5 h. The unit cell reflections for (001) Fe20s are indicated by circles. C Evolution of the conversion to styrene as function of time on stream under the conditions given in (B)...

Transition metal surfaces enriched with S, Se and Te, have been considered as candidates for DAFC cathode catalysts [112-115], For example, ruthenium selenium (RuSe) is a weU-studied electro-catalyst for the ORR [116, 117]. The ORR catalysis on pure Ru surfaces depends on the formation of a Ru oxide-like phase [118]. Ru is also an active catalyst for methanol oxidation. On the other hand, the activity of the ORR on RuSe is found not be affected by methanol [116]. RuS, has also been reported insensitive to methanol [119-122], DPT studies of model transition metal surfaces have provided with atomistic insights into different classes of reactions relevant to fuel cells operation, such as the hydrogen evolution [123], the oxygen reduction [124], and the methanol oxidation [125] reaction. Tritsaris, et al. [126] recently used DPT calculatimis to study the ORR and methanol activation on selenium and sulfur-containing transition metal surfaces of Ru, Rh, Ir, Pd, Co and W (Fig. 8.9). With RuSe as a starting point, the authors studied the effect of the Se on... 

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