Ionic conduction in Sn1−xScxP2O7 for intermediate temperature fuel cells

A novel series of mixed ion conductors, Sn1−xScxP2O7 (x = 0.03, 0.06, 0.09, 0.12), were synthesized by a solid-state reaction method. The conduction behaviors of the ion conductors in wet hydrogen atmosphere were investigated by some electrochemical methods including AC impedance spectroscopy, gas concentration cells in the temperature range of 323–523 K. It was found that the doping limit of Sc3+ in SnP2O7 was between 9 mol% and 12 mol%. The highest conductivity was observed to be 2.76 × 10−2 S cm−1 for the sample of x = 0.06 under wet H2 atmosphere at 473 K. The ionic conduction was contributed mainly to proton and partially to oxide ion in wet hydrogen atmosphere from 373 K to 523 K. The H2/air fuel cells using Sn1−xScxP2O7 (x = 0.03, 0.06, 0.09) as electrolytes (1.7 mm in thickness) generated the maximum power densities of 11.16 mW cm−2 for x = 0.03, 25.02 mW cm−2 for x = 0.06 and 14.34 mW cm−2 for x = 0.09 at 423 K, respectively. The results indicated that Sn1−xScxP2O7 is a promising solid electrolyte system for intermediate temperature fuel cells.