The importance of electrode material in environmental electrochemistry: Formation and reactivity of free hydroxyl radicals on boron-doped diamond electrodes

A model describing the hydroxyl radical (HO) concentration profile at the boron-doped diamond (BDD) electrode, in the presence and absence of organic compounds, is presented. It is shown that this profile depends strongly on the reaction rate constant between the HO and the organic compound. Furthermore, it is shown that the presence of organics affects the current–potential (I–V) curves. In fact, the higher the reaction rate between organics and HO, the higher is the shift of the I–V curves toward lower potential with respect to oxygen evolution. Supposing that water discharge to free hydroxyl radicals on BDD is governed by Nernst equation, this shift of the I–V curves toward lower potentials has been calculated and compared with the experimental data obtained on BDD using two model compounds: methanol and formic acid.