Ionic conduction in Sn_(1_x)Sc_xP_2O_7 for intermediate temperature fuel cells

摘要

A novel series of mixed ion conductors, Sn_(1_x)Sc_xP_2O_7(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 Sc~(3+) in SnP_2O_7 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 H_2 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 H_2/air fuel cells using Sn_(1_x)Sc_xP_2O_7 (x-0.03,0.06,0.09) as electrolytes (1.7mm in thickness) generated the maximum power densities of 11.16 mW cm~(-2) for x-0.03,25.02 mW cm~(-2) forx-0.06and 14.34 mW cm~(-2) for x=0.09 at 423 K, respectively. The results indicated that Sn_(1_x)Sc_Xp_2O_7is a promising solid electrolyte system for intermediate temperature fuel cells.