Ionic Transport Properties of P₂O₅-SiO₂ Glassy Protonic Composites Doped with Polymer and Inorganic Titanium-based Fillers

• Main Authors: Maciej Siekierski, Maja Mroczkowska-Szerszeń, Rafał Letmanowski, Dariusz Zabost, Michał Piszcz, Lidia Dudek, Michał M. Struzik, Magdalena Winkowska-Struzik, Renata Cicha-Szot, Magdalena Dudek
• Format: Article
• Language: English
• Published: MDPI AG 2020-07-01
• Series: Materials
• Subjects: protonic composite conductors; medium temperature PEM fuel cell; sol–gel; phosphosilicate glass; PVA; PEO polymeric additives
• Online Access: https://www.mdpi.com/1996-1944/13/13/3004

This paper is focused on the determination of the physicochemical properties of a composite inorganic–organic modified membrane. The electrical conductivity of a family of glassy protonic electrolytes defined by the general formula (P₂O₅)_x(SiO₂)_y, where x/y is 3/7 are studied by Alternating Current electrochemical impedance spectroscopy (AC EIS) method. The reference glass was doped with polymeric additives—poly(ethylene oxide) (PEO) and poly(vinyl alcohol) (PVA), and additionally with a titanium-oxide-based filler. Special attention was paid to determination of the transport properties of the materials thus modified in relation to the charge transfer phenomena occurring within them. The electrical conductivities of the ‘dry’ material ranged from 10⁻⁴ to 10⁻⁹ S/cm, whereas for ‘wet’ samples the values were ~10⁻³ S/cm. The additives also modified the pore space of the samples. The pore distribution and specific surface of the modified glassy systems exhibited variation with changes in electrolyte chemical composition. The mechanical properties of the samples were also examined. The Young’s modulus and Poisson’s ratio were determined by the continuous wave technique (CWT). Based on analysis of the dispersion of the dielectric losses, it was found that the composite samples exhibit mixed-type proton mobility with contributions related to both the bulk of the material and the surface of the pore space.