The Influence of Heterogeneous Dopant Porous Structure on the Properties of Protonic Solid Electrolyte in the CsHSO4-SiO2 System
Solid State Ionics
||Composite electrolyte, Protonic conductor
Institute of Solid State Chemistry and Mechanochemistry SB RAS
Boreskov Institute of Catalysis SB RAS
Transport, thermal and structural properties of (1−x)CsHSO4–xSiO2 (where x=0–0.9) composite solid electrolytes have been studied by complex impedance, DSC and X-ray diffraction methods. The used highly dispersed silica are different in their specific surface area (13–580 m2/g), pore size (R=14–1000 Å) and pore size distribution. It was shown that the low-temperature phase conductivity of composites is ca 2–2.5 orders of magnitude higher than that of the individual CsHSO4. Composite properties depend on content and pore size of SiO2. The low-temperature phase conductivity is maximum at x=0.5–0.7. The optimum pore size of heterogeneous dopant is in a range of 35–100 Å, where the most composite conductivity increase takes place and thermodynamic and structural properties change markedly (`dimensional effect'). For composites based on these silicas the enthalpies of CsHSO4 superionic phase transition and melting considerably decrease. As x increases the ionic component becomes either partially or completely amorphous. The CsHSO4 dispersion most likely proceeds in composites based on silica, the pore size of which is 170 Å.