Electro-catalytic oxidation of phenol on several metal-oxide electrodes in aqueous solution.

Elecrtochemical degradation of phenol was evaluated at five typical anodes for mineralization to carbon dioxide or for being a pre-treatment method in toxic aromatic compounds. Three kinds of RuO(2)-base electrodes were prepared by thermal deposition, which were coated by the oxides of Ru or by Ru, Sn and Sb or by Ru, Sn, Sb and Gd on Ti metal surface, respectively. Another electrode Ti/ PbO(2) was prepared by electro-deposition method with PbO(2) coated on Ti. A Pt electrode was chosen for comparison. Characteristics of the typical five electrodes were investigated by cyclic voltammetry, SEM and its degradation ability for phenol. Performance for phenol degradation of the three RuO(2) electrodes lie in: Ti/Sb-Sn-RuO(2)-Gd> Ti/Sb-Sn-RuO(2)> Ti/RuO(2) and the electrode with beta-PbO(2) coating was superior to RuO(2)-based electrodes and Pt electrode. Aromatic ring opening take place at all researched electrodes and it is supposed that electrolysis run stop at different intermediates, such as benzoquinone, maleic acid, etc. Under the present experimental conditions, whole mineralization to CO(2) takes place only in the beta-PbO(2) anode. A pathway of electrochemical degradation of phenol was suggested based on the experimental analysis.