Electrochemical Oxidation of Carboxylic Acids in Water at Boron-Doped Diamond (BDD) Anodes in the Range of Potential of Oxygen Evolution: Detection Measurements and Studies on the Reaction Mechanism

The electrochemical oxidation in water solutions of selected carboxylic acids (namely oxalic, formic, acetic, maleic, and succinic) at boron-doped diamond (BDD) anodes was investigated by polarization and chronoamperometric measurements. In the presence of low concentrations of carboxylic acids, current densities changed approximately linearly with the acid concentrations. Furthermore, when the current densities were plotted as a function of the chemical oxygen demand, a similar response was observed for all the investigated acids with the exception of oxalic acid. For high carboxylic acid concentrations, the linear variation is often loosen and different behaviors are observed depending on the nature of the acid and on the value of the applied working potential. Smaller increases of current densities were observed in water solutions of NaCl as a result of the chlorides oxidation to active chlorine. The effect of pH, boron doping level, BDD pretreatment, and of the nature of the supporting electrolyte on the amperometric response of carboxylic acids was also studied in detail. Some theoretical considerations were briefly presented in order to rationalize the observed behaviors.