Comparative study of oxidation ability between boron-doped diamond (BDD) and lead oxide (PbO₂) electrodes

The electrochemical oxidation capabilities of two high-performance electrodes, the boron-doped diamond film on Ti (Ti/BDD) and the lead oxide film on Ti (Ti/PbO₂), were discussed. Hydroxyl radicals (·HO) generated on the electrode surface were detected by using p-nitrosodimethylaniline (RNO) as the trapping reagent. Electrochemical oxidation measurements, including the chemical oxygen demand (COD) removal and the current efficiency (CE), were carried out via the degradation of p-nitrophenol (PNP) under the galvanostatic condition. The results indicate that an indirect reaction, which is attributed to free hydroxyl radicals with high activation, conducts on the Ti/BDD electrode, while the absorbed hydroxyl radicals generated at the Ti/PbO₂ surface results in low degradation efficiency. Due to quick mineralization which combusts PNP to CO₂ and H₂O absolutely by the active hydroxyl radical directly, the CE obtained on the Ti/BDD electrode is much higher than that on the Ti/PbO₂ electrode, notwithstanding the number of hydroxyl radicals produced on PbO₂ is higher than that on the BDD surface.