Corrosion of graphite electrode in electrochemical advanced oxidation processes: Degradation protocol and environmental implication

Abstract

Carbon corrosion is a pivotal problem influencing the performance of carbon electrode in electrochemical advanced oxidation processes (EAOPs). In this work, the sensitivity of graphite electrode to corrosion is evaluated under typical homogeneous electro-Fenton (EF) and anodic oxidation (AO)-assisted O2 oxidation conditions. Carbon oxidation reaction (COR) involved in these EAOPs is explored, and its impact on electrode activity is determined. The result of cyclic voltammetry suggests the COR under homogeneous EF condition is caused by reactive oxygen species (ROS), and both the electro-oxidation and ROS might contribute to COR under AO-assisted O2 oxidation condition. Product characterization identifies surface oxygenated species, soluble organic carbon and CO2 as the products of COR. Mass change indicates surface oxygenated species are the main products under homogeneous EF condition, but carbon dissolution prevails the COR under AO-assisted O2 oxidation condition. The potential used on the graphite electrode is recommended to be above −0.86 V in homogeneous EF process or below 1.34 V in AO-assisted O2 oxidation process. The COR occurring within the recommended potential range enhances the efficiency of EAOPs due to formation of surface oxygenated species. Excurses beyond the potential range would cause significant dissolution of graphite electrode that foresees electrode deterioration.