Effect of pressure on through-plane proton conductivity of polymer electrolyte membranes

• Published in: Journal of membrane science 2012-11, Vol.417-418, p.210-216
• Main Authors: Yun, Sung-Hyun, Shin, Sung-Hee, Lee, Ju-Young, Seo, Seok-Jun, Oh, Se-Hun, Choi, Young-Woo, Moon, Seung-Hyeon
• Format: Article
• Language: English
• Subjects: Anisotropic conduction; artificial membranes; Chemistry; Colloidal state and disperse state; Contact resistance; Electrochemical impedance spectroscopy; Electrochemistry; electrolytes; energy conversion; Exact sciences and technology; General and physical chemistry; impedance; Membranes; Polymer electrolyte membranes; polymers; Through-plane conductivity; viscoelasticity; water treatment
• ISSN: 0376-7388; 1873-3123
• DOI: 10.1016/j.memsci.2012.06.041

This study reports an electrochemical analogy with the invention of a 2-electrode impedance cell oriented to analyze through-plane ionic conductivity of polymer electrolyte membranes. The membranes are utilized under varied pressures in assembled membrane stacks for water treatment, energy conversion, and storage devices. In addition, polymeric membranes are a viscoelastic material, which allow their shape to change according to the external pressure. Therefore, the impedance under controlled pressure is crucial information for analyzing their electrochemical properties. In this regards, an apparatus is designed to indicate the absolute pressure in the sample and the resulting thickness of the sample while measuring the impedance. As a model analysis, we employ a proton conducting membrane, Nafion®117, Nafion®115, and Nafion®112. The membrane thickness in a wet state was found to be significantly variable with the pressure, and the impedance spectra showed a clear dependence on the pressure. Therefore, this new approach facilitates a precise impedance analysis, since the exact sample thickness is indicated, along with the absolute pressure in the sample. As such, this technique could be a useful tool for analyzing the through-plane conductivity of polymer electrolyte membranes with high accuracy. [Display omitted] ► An improved 2-electrode cell is developed for through-plane EIS analyses. ► The cell is designed to reproduce the actual suppressing pressure to a membrane. ► Significant thickness changes of the membrane under a pressure are defined. ► An electrochemical EIS analogy is presented based on the equivalent circuit model. ► Through-plane proton conductivity of a polymer electrolyte membrane is analyzed.