Abstract Herein, we explore selectivity toward generation of ClOx (x=1-4) anions and durability of commercial polycrystalline free-standing boron-doped diamond (BDD) electrodes in synthetic ASTM seawater oxidation. 10 min electrooxidation experiments at current densities from 1 to 100 mA/cm2 revealed formation of ClO-, ClO3-, and ClO4- anions. ClO- anions were found to be the dominant reaction product, with concentrations exceeding those of ClO3- and ClO4- by two and five orders of magnitude, respectively. The same trend was observed in 0.5M NaCl at pH 8.2 that was used as a reference, although the ClO3- concentration was found to be ca 30% higher. ClO- ions were generated in seawater with ca 85% Faradaic efficiency (FE), which was lower than that in 0.5M NaCl. This difference was attributed to parasitic reactions of ClO- with trace elements and organic impurities present in seawater. We demonstrated that radical scavengers such as H3BO3 and HCO3- present in seawater do not affect FEs of the ClO- production. 
 The 48 h durability tests demonstrated a slight performance decay, more pronounced in seawater. Performance decay was accompanied by the BDD surface oxidation with formation of carbonyl, carboxyl and hydroxyl groups, dominated by OH groups.