Electrocatalytic activity oxygen evolution

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... 

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 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. 

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. 

Other approaches have focused upon using non-precious metals and their oxides as alternatives to the platinum catalysts. For example, the mixed oxide catalysts of the binary and ternary alloys of noble metals and transition metals have been investigated for the oxygen evolution reaction in solid polymer electrolyte water electrolyzers. Binary, ternary, and quaternary platinum alloys with base metals of Cu, Ni, and Co have been used as electrocatalysts in liquid acid electrolyte cells. It was also reported that a R-Cu-Cr alloy displayed better activity to oxygen reduction than R and Pt-Cr in liquid electrolyte.The enhanced electrocatalytic activity of these types of alloys has been attributed to various factors, including the decrease of the nearest neighbor distance of platinum,the formation of Raney type... 

Parallelism in the specific inhibition of electrocatalytic and enzymatic activity. The specific inhibitors of a particular enzyme are observed also to suppress its electrocatalytic activity in the adsorbed state. Experimental data demonstrate that a,a -dipyridyl completely suppresses the reaction of hydrogen evolution by immobilized hydrogenase fluorine ions inactivate laccase in the reaction of oxygen electroreduction and diphenylhydrazine has the same effect on peroxidase in the reaction of hydrogen peroxide electroreduction. A complete parallelism is also observed in the inactivating effect of hydrogen peroxide on peroxidase in the electrochemical reaction and enzymatic oxidation of o-dianisidine. 

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