Revealing electron transfer mechanisms of microelectrolysis for pollutant degradation by a dual electrode approach

Abstract

Microelectrolysis has been proven to be a practical technology for the catalytic elimination of pollutants in wastewater. This study presents a research method focusing on the demonstration of electron transfer in microelectrolysis through a dual-electrode unit. 2,4-Dichlorophenol, sodium isobutyl xanthate and sodium diethyldithiocarbamate were taken as the typical pollutants for degradation. The results of electrochemical tests and quantum chemical calculations indicated that the ΔG among electron transfer steps proceeding on cathodes is the internal factor deciding the electron flow kinetics between the anode and cathode. The electron transfer rate is influenced by the electron transfer step with a ΔGmax in the oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) of the cathode process and is restricted by the number of active sites on the cathode surface. Organics that react with intermediates formed in electrochemical chain reactions promote the entire electron transfer process between the poles, while organics that increase cathode electronegativity have the opposite effect. The cathode products of ·OH, ⋅H, ⋅OOH/⋅O2—, and H2O2, which are derived from the ORR and HER processes, are important for pollutant degradation. Catalysts can be selected and designed based on the required active substance and solution chemical environment for the degradation of targeted contaminants. This study elucidates the electrode kinetics of microelectrolysis, which can be the inspirational basis for catalyst design and technology application.