Understanding active chlorine species production using boron doped diamond films with lower and higher sp3/sp2 ratio

• Ratio sp3/sp2 has a great influence on chlorine speciation during electrolysis with diamond electrodes
• BDD anode with high sp3/sp2 is suitable in disinfection applications, avoiding hazardous species
• BDD with high graphite content could be considered a much better electrocatalyst for o.e.r.
• High graphite content favors electrocatalytic conversion of chloride into ClO2−, Cl2, ClO− and ClO2 to ClO4−.

The present study was motivated by the reports that promote the use of boron doped diamond (BDD) anode for electrochemical disinfection. The discussion about the production of undesirable active chlorine species on diamond films is still open. For this reason, the influence of sp3/sp2 ratio on the performance on the evolution of chlorine-related species was investigated by polarization and electrolytic techniques in order to establish whether their formation and consumption related to either chemical or electrochemical reactions. The results demonstrated that dissolved Cl2, ClO2−, ClO2, ClO3− and ClO4− species can be electrochemically formed at both BDD electrodes. However, the concentration trends are different, indicating that the relation of sp3/sp2 ratio has a key role in the electrochemical route to produce ClO3− and ClO4−.