Voltammetric study of formic acid oxidation via active chlorine on IrO2/Ti and RuO2/Ti electrodes

This work aimed to contribute to the mechanism electrochemical oxidation study of organic compounds on DSA electrodes. To do this, IrO2 and RuO2 electrodes were prepared thermally at 40°C on Titanium substrate. The prepared electrodes were characterized using voltammetric and SEM techniques. The electrochemical measurements in acid media made it possible to show the presence of IrO2 and RuO2 on the surface of the electrode. These electrodes have identical electrocatalytic behaviors both for oxygen evolution and chlorine evolution. The prepared electrodes make it possible to oxidize the organic compounds in an acid media in the absence or in the presence of Cl-. In acidic electrolytes, water molecules produce hydroxyl radicals that contribute to the higher oxides (RuO3 or IrO3) formation. The higher oxides obtained produce O2 and regenerate the active sites of our electrodes. In the electrolytes containing chlorides, higher oxides fix them (IrO3(Cl) or RuO3(Cl)) in competition with the production of O2. Then IrO3(Cl) or RuO3(Cl) reacts with Cl- to produce Cl2 and regenerate the adsorbed hydroxyl radicals. The higher oxides also react as a mediator in HCOOH oxidation in competition with O2 evolvement. In the electrolytes containing HCOOH and Cl-, the organic pollutant's oxidation occurs indirectly via the hypochlorite ions produced in the solution and on the electrodes. This study showed that the produced OH· and Cl2 in situ are involved in the oxidation of HCOOH