Synthèse, caractérisation et utilisation de matériaux composites à base de POC + MnO2 comme matériaux d'électrodes dans les piles Zn-MnO2

Abstract

he preparation of composite materials based on conductive polymers (CPs) and MnO₂ for use in electrochemical generators and electrocatalysis—specifically as modified electrodes for oxygen reduction in alkaline media. In this study, composite materials were synthesized via the electrodeposition of polybithiophene (PBTh) and polypyrrole (PPy) onto the surfaces of γ-MnO₂ and β-MnO₂ oxides. This electrodeposition was carried out using cyclic voltammetry. The voltammograms revealed an increase in the peak currents for both reduction and oxidation during cycling. This phenomenon was attributed to changes in kinetic behavior, likely resulting from a significant capacitive current contribution and modifications to the γ-MnO₂ and β-MnO₂ grain surfaces. Cyclic voltammetric analysis confirmed the presence of the conductive organic polymer on the electrode surface. Impedance measurements revealed a charge-transfer process at high frequencies followed by a purely diffusion-controlled process at low frequencies; these were characterized, respectively, by a capacitive arc (with a center shifted below the real axis) and a straight line with a 45° slope. Furthermore, it was observed that polymer incorporation influenced the electrochemical impedance parameters. Specifically, the charge-transfer resistance of γ-MnO₂ decreased during the electrodeposition of PBTh and PPy, whereas the charge-transfer resistance of β-MnO₂ increased in the presence of PBTh and PPy. An equivalent circuit has been proposed in which the capacitive component of the double layer is replaced by a constant phase element (CPE).