Platinum peroxide-radical mechanism

Because of the irreversible and not well-understood change of the electrocatalyst surface above 1.0 V, early mechanistic studies were conducted under ill-defined conditions. Thus, while anodic evolution of Oj takes place always in the presence of oxygen-covered electrodes, the cathodic reaction proceeds on either oxygen-covered or oxygen free surfaces with different mechanisms (77,158). The electrochemical oxide path, proposed for oxide-covered platinum metals in alcaline electrolytes (759,160), has been criticized by Breiter (7), in view of the inhibition of oxygen reduction by the oxygen layers. Present evidence points to the peroxide-radical mechanism (77,... 

In non-aqueous solutions the Kolbe electrosynthesis takes place with high eflSciency at platinized platinum and gold, as well as at smooth platinum, anodes increase of temperature and the presence of catalysts for hydrogen peroxide decomposition, both of which have a harmful effect in aqueous solution, have relatively little influence. The mechanism of the reaction is apparently quite different in non-aqueous solutions and aqueous solutions in the former no hydroxyl ions are present, and so neither hydroxyl radicals nor hydrogen peroxide can be formed. It is probable, therefore, that direct discharge of acetate ions occurs at a potential which is almost independent of the nature of the electrode material in a given solvent. The resulting radicals probably combine in pairs, as in aqueous solution, to form acetyl peroxide, which subsequently decomposes as already described. ... 

Several mechanisms for curing gels are possible however, most have limitations involving either processing or the final gel properties. Condensation type cures form water or alcohol by-products which cause outgassing and voids. Free radical peroxide-activated addition cures make it difficult to control gel consistency from batch to batch. These problems are not evident in the most prevalent cure mechanism used today, the addition of silicon-bonded hydrogen atoms to silicon-bonded olefinic radicals, usually vinyl, in the presence of a few parts per million of a platinum catalyst (I). This system creates no by-products and is easily controlled. 

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