Influence of supporting electrolyte on the electrochemical oxidation of formic acid on boron-doped diamond electrodes

The influence of support electrolyte on the electrochemical degradation of formic acid was studied on boron-doped diamond (BDD) electrodes. Experimental data are compared with a theoretical model, which is based on organic degradation via hydroxyl radicals under current or mass transport controlled regimes depending on the difference between the applied and limiting current. The kinetics of the different reactions involved in the process is also briefly studied. It is shown that when sulfuric acid is used as support electrolyte, the reactions involving electro-generated peroxodisulfate anions during the degradation of formic acid are highly dependent on temperature. For this reason, the influence on the overall process of the chemical reaction between these anions and formic acid tends to increase with increasing temperatures and when the electrolysis becomes controlled by mass transport. However, it is proven that degradation of formic acid in the bulk occurs under current controlled regime as well. Furthermore, it is shown that the use of sulfuric acid as support electrolyte enhances the degradation of formic acid at high temperatures and when the process is controlled by mass transfer compared to other inert support electrolytes.