Role of Hydroxyl Radicals During the Competitive Electrooxidation of Organic Compounds on a Boron-Doped Diamond Anode

A numerical model has been developed to estimate the role of hydroxyl radicals in the competition of organic compounds during electrolysis using a boron-doped diamond (BDD) anode. It is well established that hydroxyl radicals are generated during water discharge. These radicals are free at the surface and act locally, their sphere of activity was estimated by the model to be 20 nm maximum from the anode. The implementation of the model taking account the presence of one and then two organic compounds in the solution can be used to predict the variation of the concentration of each organic with time during the electrolysis and their space profile in the electrochemical reactor too without using adjustable parameters. The role of hydroxyl radicals was highlighted in the competitive reaction with organics: the electrolysis of a solution containing an equimolar mixture of formic acid (FA) and maleic acid (MA) shows that FA oxidation only began when the MA had completely disappeared. The numerical model is in good agreement with the experiment and is thus suitable to describe the competition of two organics during electrolysis with a BDD anode.