The Electrocatalytic Oxygen Reduction Property And Application Studies Of Conducting Polymers Composite Film Electrode

Conducting polymers have been applied in many fields because of convenience of preparation, harmlessness, high conductivity and environmental stability. Recently, the conducting polymer composite materials have been paid much attention because of the poor mechanical properties of pure conductive polymers. On one hand, the conductive polymer composite materials hold their primary properties, and on the other hand their mechanical properties have been improved at a certain extent.Recently, the electrochemical reduction of oxygen has also been widely studied on anthraquinones and their various derivatives modified electrodes,, since the surface modification of electrodes with anthraquinones greatly increase the rate of oxygen reduction to hydrogen peroxide (H2O2). However, anthraquinones and their various derivatives which are grafted as spontaneously adsorbed or covalently bound monolayer on the electrode surface, tend to desorb from the surface during the long-term operation, leading to a loss of electrocatalytic ability and stability of the working electrodes. So, how to improve the stability and the electrocatalytic activity of the anthraquinones derivatives modified electrodes becomes a research hotspot. In addition, homogeneous electro-Fenton systems have some well-known drawbacks, e.g. a limited pH range, the production of iron-containing waste sludge which is difficult to dispose, and the catalyst deactivation by some iron complexing agents like phosphates anions, that is why the development of heterogenerous electro-Fenton systems that causes extensive attention in the subject of electrochemical, especially for wastewater treatment.In this work, the functionalized PPy film with anthraquinone-monosulphonate (AQS) incorporated as dopant was prepared by electrochemical anodic polymerization of pyrrole (Py) at a glassy carbon electrode from aqueous solution. The prepared AQS/PPy hybrid film was characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopic (FTIR). The results showed that anion AQS can realize the doping in the process of Py monomer electrochemical oxidation polymerization, synthesizing the conductive polymer composite film with porous structure. The electrochemical behavior of AQS in PPy matrix was investigated in various pH solutions using cyclic voltammetry (CV) and chronoamperometry/chronocoulometry, a single two-electron reduction step was observed for the resulting composite film in donor's media. AQS/PPy hybrid film exhibits good stability and electrochemical reproducibility.The electrocatalytic reduction of oxygen on the AQS/PPy composite film was also investigated in detail in various pH solutions using various electrochemical techniques such as CV, chronoamperometry/chronocoulometry, rotating disk electrode (RDE), rotating ring-disk electrode (RRDE), Tafel polarity and electrochemical impedance spectroscopy (EIS). It was found that the conductive polymer composite film exhibits obvious catalytic behavior on the electrochemical reduction of oxygen into hydrogen peroxide (H2O2). The doping AQS is an effective mediator for the reduction of oxygen and the H2AQS is responsible for the enhanced catalytic activity. The PPy film can further reduce H2O2 to H2O in the potential range more negative than the potential range where the two-electron reduction of oxygen proceeds efficiently on the AQS sites.In addition, heterogeneous electro-Fenton-like system has been constructed by the AQS/PPy composite membrane modified spectrum pure graphite and the catalyst CuO/γ-Al2O3. The azo dye decay were determined as a function of temperature, catalyst dosage. The system operation optimization conditions have been found. Further, the stability and regeneration of the heterogeneous catalysts were also investigated under the optimum reaction conditions.