Corrosion And Modification Of Carbon Electrode In Electrocatalytic Oxidation Of Organic Pollutants

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.The carbon materials are modified for getting composite materials which are applied to the treatment of environmental wastewater,Oxygen?O₂?activation for oxidative reaction of pollutants at room temperature is important for pollution control.Herein,we report synthesis of an unsaturated MnO catalyst confined in a porous carbon matrix on a graphite felt support?MnO@C/GF?,which shows high catalytic activity in electro-activation of O₂ for oxidation of various pollutants.The electro-assisted catalytic wet air oxidation?ECWAO?process on anodic MnO@C/GF is able to completely mineralize different dyes including crystal violet,neutral red,and fushine basic,and mineralize typical pharmaceuticals and personal care products,i.e.bisphenol A,ibuprofen and tetracycline,at efficiencies of 91.2%,85.1%and 75.1%,respectively.Mechanistic study indicates the oxidation of organic pollutants in the ECWAO process involves chemisorption of O₂ on MnO,activation of chemisorbed oxygen species via electro-oxidation reaction,and oxidation of organic pollutants by the activated chemisorbed oxygen species.The carbon matrix prevents the MnO leaching from the MnO@C/GF composite during the ECWAO process,thus endowing the composite with excellent stability and reusability.The ECWAO process developed in this work demonstrates the merits of high efficiency,low energy input and environmental friendliness,and exhibits a great potential for practical wastewater treatment under mild condition.