Catalytic Degradation of an Organic Dye through Electroreduction of Dioxygen in Aqueous Solution

Oxygen reduction reaction (ORR) was carried out electrochemically at glassy carbon (GC), platinum, copper and nickel electrodes in acidic solution using cyclic voltammetry in absence and in presence of an organic dye, methylene blue (MB). Four-and two-electron ORR occurred at platinum and GC electrodes, respectively, whereas no well-defined ORR took place at nickel and copper electrodes. Although MB was found to be electrochemically inactive, the electrochemical behavior, especially, change in the peak potential and current in the cyclic voltammetric results in the presence of MB at platinum and GC electrodes varied interestingly. MB underwent following chemical reaction with the reactive oxygen species (ROS) generated in situ during ORR as supported by steady-state hydrodynamic voltammetric measurements. Ultraviolet-visible spectral behavior of MB changed when it was allowed to react with ROS generated by bulk electrolysis of O2 at a GC plate electrode. It was revealed that electrochemical ORR is a promising route for degradation of an organic dye in aqueous solution.