Self-discharge in positively charged polypyrrole-cellulose composite electrodes

Self-discharge is one of the most critical issues to address to allow for industrialization of conducting polymer (CP) based electric energy storage devices. The present work investigates the underlying cause of self-discharge in positively charged polypyrrole (PPy), which is one of the most frequently studied CPs for such devices. The analyzed material is a composite of PPy and cellulose from Cladophora sp. algae forming a free standing paper-like material. From the time dependence of the potential decay as well as from independent spectroelectrochemical investigations the decay was attributed to a kinetically limiting Faradaic reaction, intrinsic to the polymer, forming a reactive intermediate that irreversibly reacts with its surroundings in a kinetically non-limiting following reaction. As such, nucleophilic addition of electrolyte nucleophiles is not found to be rate-determining. These results provide insight into the self-discharge phenomenon in p-doped CPs, and information regarding the potential range in which CPs can operate with insignificant self-discharge.