Oxygen evolution, electrocatalytic

In acid electrolytes, carbon is a poor electrocatalyst for oxygen evolution at potentials where carbon corrosion occurs. However, in alkaline electrolytes carbon is sufficiently electrocatalytically active for oxygen evolution to occur simultaneously with carbon corrosion at potentials corresponding to charge conditions for a bifunctional air electrode in metal/air batteries. In this situation, oxygen evolution is the dominant anodic reaction, thus complicating the measurement of carbon corrosion. Ross and co-workers [30] developed experimental techniques to overcome this difficulty. Their results with acetylene black in 30 wt% KOH showed that substantial amounts of CO in addition to C02 (carbonate species) and 02, are... 

In this section we treat some electrochemical reactions at interfaces with solid electrolytes that have been chosen for both their technological relevance and their scientific relevance. The understanding of the pecularities of these reactions is needed for the technological development of fuel cells and other devices. Investigation of hydrogen or oxygen evolution reactions in some systems is very important to understand deeply complex electrocatalytic reactions, on the one hand, and to develop promising electrocatalysts, on the other. 

M. Faraday was the first to observe an electrocatalytic process, in 1834, when he discovered that a new compound, ethane, is formed in the electrolysis of alkali metal acetates (this is probably the first example of electrochemical synthesis). This process was later named the Kolbe reaction, as Kolbe discovered in 1849 that this is a general phenomenon for fatty acids (except for formic acid) and their salts at higher concentrations. If these electrolytes are electrolysed with a platinum or irridium anode, oxygen evolution ceases in the potential interval between +2.1 and +2.2 V and a hydrocarbon is formed according to the equation... 

The presence of iron in nickel oxyhydroxide electrodes has been found to reduce considerably the overpotential for oxygen evolution in alkaline media associated with the otherwise iron free material.(10) An in situ Mossbauer study of a composite Ni/Fe oxyhydroxide was undertaken in order to gain insight into the nature of the species responsible for the electrocatalytic activity.(IT) This specific system appeared particularly interesting as it offered a unique opportunity for determining whether redox reactions involving the host lattice sites can alter the structural and/or electronic characteristics of other species present in the material. 

The Ru02 anode is at a clear advantage. Without treating the details of the electrocatalytic reaction—which have been dealt with by other authors (11, 23-25)—the mechanism is likely to be similar to that described by Krasil shchikov (11) [Eqs. (7a)-(7c)] for anodic oxygen evolution. The same type of mechanism is also operative with anodic 02 evolution at Ru02 anodes. 

Electrocatalytic oxidation of glyoxal on platinum in perchloric acid medium at fixed potential in the oxygen evolution region. 

The electrocatalytic behavior of olefins was studied by Zanta et al. (2000) at thermally prepared ruthenium-titanium- and iridium-titanium-dioxide-coated anodes. The aliphatic olefins were shown to be inactive in the region before oxygen evolution, while aromatic ones showed one or two oxidation peaks, and the catalytic activity seemed to be the same for both substrates. However, as for platinum anodes, voltammetric studies and FTIR analyses have also shown the formation of a polymeric film that blocks the surface of the electrode and decreases its activity. 

The radius of Ru atom is in the middle of that of Sn atom and Ti atom. The three elements can form stabilized solid solution during thermal oxidation and it can resist the formation of nonconductive Ti02. That is the reason why Sn02 electrode with interlayer processes longer service life. Ru02 coating has low oxygen evolution potential, which will result in low electrocatalytic... 

Relatively little information is available on the electrocatalytic activity of thermally prepared rhodium oxide for oxygen evolution, this oxide having been investigated for the most part in conjunction with other oxide catalysts [242, 243], A Tafel slope of ca. 50 mV decade-1 has been observed at low... 

The kinetics of oxygen evolution have been investigated at a variety of perovskite oxides, mainly in alkaline solution. Notwithstanding the work of Bockris and co-workers [269] on the electrocatalytic activity of the perovskite analog oxide Nax W03 for oxygen reduction, the first report of a study of the electrocatalytic activity of perovskite oxides was by Meadowcroft [270] for oxygen reduction on La(1 l)SrICo03. 

There is a need to develop new types of oxide electrodes for reactions of technological importance with emphasis on both high electrocatalytic activity and stability. For example, pyrochlore-type oxides, e.g. lead or bismuth ruthenates, have shown excellent catalytic activity for the oxygen evolution and reduction reactions and should be further investigated to elucidate the reasons for such high activity. The long term stability of such ruthenate electrodes is questionable, however. 

What has been written so far in this chapter has come primarily from the thoughts of the author, and has arisen from the ideas of many physical electrochemists and their students and collaborators, not forgetting my own. But now I want to tell you about some electrocatalysts called perovskites and their electrocatalytic action on oxygen evolution from alkaline solution. One of the reasons I want... 

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