EQCM study of redox properties of PEDOT/MnO<Subscript>2</Subscript> composite films in aqueous electrolytes

Electrochemical behavior of poly-3,4-ethylenedioxythiophene composites with manganese dioxide (PEDOT/MnO₂) has been investigated by cyclic voltammetry and electrochemical quartz crystal microbalance at various component ratios and in different electrolyte solutions. The electrochemical formation of PEDOT film on the electrode surface and PEDOT/MnO₂ composite film during the electrochemical deposition of manganese dioxide into the polymer matrix was gravimetrically monitored. The mass of manganese dioxide deposited into PEDOT at different time of electrodeposition and apparent molar mass values of species involved into mass transfer during redox cycling of PEDOT/MnO₂ composites were evaluated. It was found that during the redox cycling of PEDOT/MnO₂ composite films with various MnO₂ content, the oppositely directed fluxes of counterions (anions and cations) occur, resulting in a change of the slope of linear parts of the Δf–E plots with changing the mass fraction of MnO₂ in the composite film.Rectangular shape of cyclic voltammograms of PEDOT/MnO₂ composites with different loadings of manganese dioxide was observed, which is characteristic of the pseudocapacitive behavior of the composite material. Specific capacity values of PEDOT/MnO₂ composites obtained from cyclic voltammograms were about 169 F g^?1. The specific capacity, related to the contribution of manganese dioxide component, was about 240 F g^?1.     

On the evolution and application of the concept of electrochemical polarization

This paper yields an overview on the evolution of the concept of polarization applied to electrochemical systems, ranging from electrodes to cells. The historical discussion starts at the early phase of the development of electrochemistry when current-controlled measurements were possible only, and when the early definitions of polarization, depolarization and depolarizer were created. A number of contemporary handbooks, recommendations and other reference resources are listed in which these concepts are represented in various ways, from conservative definitions to attempts of redefining them. The traditional definitions are confronted with the everyday use of professional language, drawing attention to the fact that the widespread application of potential-controlled electrochemical measurements led to new meanings. Some suggestions are made that open room for the application of the term of polarization in accord with the modern methodologies, without compromising the traditional introduction of the term. Polarization-related phenomena in biological membranes are not dealt with in the present work.