Intermediate-temperature composite proton electrolyte CsH 5(PO 4) 2/SiO 2: Transport properties versus oxide characteristic

Abstract

Composite solid electrolytes (1 − x)CsH 5(PO 4) 2/ xSiO 2 ( x = 0–0.75) based on silica with different specific surface areas have been studied by the complex impedance, DSC, and X-ray diffraction methods. The proton conductivity of composites is shown to depend on the silica's specific surface area: the higher the specific surface area the stronger influence on the transport properties of composites. The maximal composite conductivity was 2.3 mS∙cm − 1 at T = 140 °C, which exceeded the conductivity of pure CsH 5(PO 4) 2 by more than one order of magnitude. The drastic changes in the transport properties of composites are governed by the salt dispersion and/or amorphisation, which are confirmed by the changes in thermodynamic parameters. An H 2/air fuel cell based on CsH 5(PO 4) 2/SiO 2 demonstrates a maximum power density of 8 mW/cm 2 at U = 0.3 V and a current density up to 80 mA/cm 2 at a short circuit.