Conductivity and Transport Properties of Aqueous Phosphotungstic and Silicotungstic Acid Electrolytes for Room-Temperature Fuel Cells

Ales Horky, Nazir P. Kherani, Gu Xu
2003 Journal of the Electrochemical Society  
Conductivity measurements were performed on phosphotungstic and silicotungstic aqueous electrolyte solutions. The conductivity obtained from complex impedance plots had non-Arrhenius dependence on temperature and could be fit by the Vogel-Tamman-Fulcher expression, T 1/2 exp͓Q c /(T-T o )͔. Conductivities reached 0.257 and 0.32 S cm Ϫ1 at 298 K for the 60 wt % phosphotungstic and silicotungstic solutions, respectively. Low concentration silicotungstic solutions obeyed the Kohlrausch relation
more » ... owing for the determination of infinite dilution molar conductivity, 1637 S cm 2 mol Ϫ1 , with the anionic species 1 4 ͓SiW 12 O 40 ͔ 4Ϫ having a molar conductivity of 237 S cm 2 mol Ϫ1 . The diffusion coefficient of the anionic species at 303 K was 4.8 ϫ 10 Ϫ6 cm 2 s Ϫ1 with a hydrodynamic radius of 5.78 Å. Analysis of the charge transference numbers indicated that the conductivity was predominantly protonic, and suitable for room-temperature fuel cells.
doi:10.1149/1.1597884 fatcat:uj7p3adtbjar5hup36v3rmc2zq