Effect of Solvent of Ionomer Dispersion on Porous Electrodes with Three Phase Boundary

Abstract

Electrichemically driven energy conversion devices requires anodic and cathodic reactions to complete their electrochemical cells. Recent energy conversion devices such as water electrolyzers or fuel cells is comprised of anodic and cathodic reactions in which gases, ions and electrons participate. In particular, the movement of proton or hydroxyl ions generated and consumed at two electrodes, i.e., anode and cathode, are essential to determine the reaction rates due to low mobility compared to electrons. Ions moved through ion conducting membranes should be transported inside electrodes to participate in anodic or cathodic reactions. Ion pathway is normally in liquid electrolyte. Regardless, the introduction of any aqueous phase in energy conversion devices causes many problems during fabrication, operation, maintenance, and so on. In addition, if gas penetration or gas evolution is one of phenomena taking place at electrodes, the electrodes should be porous. Thus, much efforts have been devoted to develop quasi-solid electrolytes such as gel polymer, ion conducting polymers, impregnation of ions in porous matrix and so on. Among the candidates, ion conducting polymers are quite often chosen as ion conducting media for energy conversion devices. The technique to introduce ion conducting polymers within electrodes for oxidation and reduction reactions is to solidify catalyst inks consisting of electrocatalyst, dispersion of ion exchangeable polymers, controlling solvents and additives by evaporation of all solvents in catalyst inks. Ion conducting polymers could be dispersed in various solvents. It causes different shapes of ion conducting polymers in solvents, for instance, cylindrical rods, a less-defined large particles, coils and so on. Such different types of ion conducting polymers form distinguished structure catalyst layers. In this study, the effect of solvents dispersing ion conducting polymers on the performance and durability of catalyst layers was investigated. Electrochemical characterization such as I-V polarization, cyclic voltammetry, impedance and so on and microscopic characterization such as SEM and TEM were carried out to evaluate the performance and durability of catalyst layers.AcknowledgmentsThis research was supported by the Hydrogen Energy Innovation Technology Development Program of the National Research Foundation (NRF) funded by the Ministry of Science, ICT, & Future Planning(NRF-2019M3E6A1063677).