The electrochemical oxidation of 4-nitroaniline and 4-nitrophenol on modified PbO₂-electrodes

Abstract

The electrochemical oxidation of p-nitroanilline and p-nitrophenol on lead dioxide anodes, modified by different ionic dopants has been investigated. The general mechanism of the oxidation of organic compounds of aromatic nature includes oxidizing of compounds to the intermediates with quinoid structure, reactions of aromatic ring opening and formation of aliphatic products (mainly acids) and in ideal case – the complete mineralization to CO2 and H2O. According to obtained results one can conclude that both reactions occur via formation of p-benzoquinon. Calculations, based on kinetic studies of the reaction, have shown that the rate constant of the degradation of the organics involved depends on the composition of the electrode material and varies due to the nature and the content of ionic additives in lead dioxide. The maximum interest for the electrochemical destruction of organic substances represents lead dioxide electrodes modified by bismuth to which a rate constant of p-nitroaniline oxidation increases in 1.6 times compared with nonmodified electrodes. Maximum electrocatalytic activity is achieved by increasing the proportion of α-phase, on the one hand, and increase the crystalline zone of oxide on the other, which leads to increased amounts of oxygen containing particles strongly bounded to the electrode surface that participate in the electrochemical oxidation of aromatic compounds.

Keywords

• electrochemical oxidation, hydroxyl radicals, lead dioxide, methanesulfonate electrolyte