Electrocatalytic behavior of the bare and the anthraquinonedisulfonate/polypyrrole composite film modified graphite cathodes in the electro-Fenton system

Conducting polypyrrole (PPy) films with anthraquinonedisulfonate (AQDS) incorporated as dopants were prepared by electropolymerization of the pyrrole monomer in the presence of anthraquinone-2,6-disulfonic acid, disodium salt on a graphite electrode from aqueous solution. Cyclic voltammetry (CV), scanning electron microscope (SEM), and Fourier transfer infrared spectroscopy (FTIR) technologies were used to characterize the resulting AQDS/PPy composite film. The electrocatalytic activities of the bare graphite and the AQDS/ PPy/graphite cathodes toward oxygen reduction and Fe2+ regeneration were studied by using cyclic voltammetry and cathodic polarization technologies. In addition, the electron-Fenton degradation of amaranth azo dye was also studied with the potentiostatic electrolysis mode, using the bare graphite and the AQDS/PPy/graphite as cathode and Fe3+ as catalyst. The results show that (i) H2O2 generation and Fe2+ regeneration mainly depend on the cathode materials utilized, (ii) solution pH, cathodic potential, and oxygen flow rate influence H2O2 accumulation and current efficiency greatly, while the effect of AQDS doping concentration is insignificant, and (iii) Fe3+ concentration influences the electro-Fenton oxidation ability and efficiency; the main oxidizing species is hydroxyl radical ((OH)-O-center dot) formed in the reaction solution from Fenton's reagent electrogenerated concurrently at the cathode.