Enhancing electrochemical production of peroxophosphates using new boron doped diamond coatings

Abstract

Two boron doped ultrananocristallyne diamond (UNC) electrodes were manufactured and compared with a standard microcrystalline commercial electrode, to clarify how their differences may affect to the production of oxidants in the electrolysis of solutions containing phosphoric acid or phosphate salts. Effects of the current density and electrolyte pH were evaluated. Significant differences were found in the production of oxidants, being the production of oxidants favored, at high current densities and alkaline pHs. The effect of the pH was explained in terms of the higher stability of the peroxodiphosphate anion in comparison with the monoperoxyphosphate acid produced at low pHs. As well, because of the improved electrostatic attraction of the anion with the anode. Despite not exhibiting the largest electrochemical surface area, the flat UNC electrode shows the best performance for this process, except for the operation at low current densities and alkaline pHs in which the porous UNC outperforms it. Better efficiencies are obtained operating at mild current densities which was explained in terms of the great significance of direct processes in the production of oxidants by electrolysis of phosphoric acid or phosphate solutions