Effect of Ionomer Binders on Performance and Durability of Catalyst Layers in Polymer Electrolyte Electrolyzers

Abstract

Hydrogen based energy conversion devices such as water electrolyzers or fuel cells require catalyst layers as electrode providing the simultaneous movement of gas, liquid, and electron. The movement of ions generated and consumed at two electrodes, i.e., anode and cathode, respectively, takes place by ionomer binders made of perfluorosulfonic acids. Ions should be transported inside electrodes to participate in anodic and 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 exchangeable polymers, impregnation of ions in porous matrix and so on. Among the candidates, ion exchangeable polymers are quite often chosen as ion conducting media for energy conversion devices. The technique to introduce ion exchangeable 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 exchangeable polymers could be dispersed in various solvents. It causes different shapes of ion exchangeable polymers in solvents, for instance, cylindrical rods, a less-defined large particles, coils and so on. Such different types of ion exchangeable polymers form distinguished structure catalyst layers. In this study, the effect of solvents dispersing ion exchangeable 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. Acknowledgment This 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).