Comparative study of oxidation ability between boron-doped diamond (BDD) and lead oxide (PbO_2) 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.