Anodic oxidation of organics on thermally prepared oxide electrodes

Electrochem. oxidn. of orgs. at thermally prepd. dimensionally stable metal oxide anodes (DSA) has been studied. In reactions involving only simple electron transfer, oxide electrodes exhibit an electrocatalytic activity similar to that of noble metal electrodes. In oxidn. reactions of more complex mechanism, oxide anodes show no electrocatalytic activity below the potential of oxygen evolution and oxidn. of orgs. can take place only under conditions of simultaneous oxygen evolution. A simplified mechanism of orgs. oxidn. catalyzed by intermediates of oxygen evolution has been proposed distinguishing between two limiting electrode behaviors: (i) At "non-active" anodes (typically fully oxidized metal oxides) oxidn. of orgs. occurs at a high potential and leads to their combustion through physisorbed hydroxyl radicals. (ii) At "active" electrodes (IrO2, RuO2) the reaction takes place at lower potentials characteristic of the metal oxide and results in a selective oxidn. of the org. compd. at higher oxidized metal oxide surface sites. A kinetic model of orgs. oxidn. competed by oxygen evolution at "active" type anodes is also proposed and confirmed by preparative electrolysis. [on SciFinder (R)]