Ionic Conduction and Power Generation Characteristics of Pr-Doped Ba 2 In 2 O 5 for Proton-Conducting SOFCs

Abstract

Highly Pr-doped Ba2In2O5 (PBI) was successfully fabricated and its ionic conduction and power generation characteristics were studied in this work. Two PBI materials of different concentration ratio were evaluated: Pr: Ba: In = 0.9: 1.1: 1 (PBI910) and Pr: Ba: In = 1: 1: 1 (PBI000). PBI910 material was confirmed as single phase with cubic perovskite structure. However, PBI000 had both cubic phase and impurity phase. In a hydrogen concentration cell, the measured proton transfer number t(H)+ of PBI910 at 500 degrees C was 0.81 and then decreased with increasing temperature, whereas the oxide ion transfer number t(O2-) was 0.07 and then increased with increasing temperature. Power generation experiments were evaluated at 500 degrees C to 900 degrees C using PBI as electrolyte and H-2 as fuel. Results revealed that t(H)+ and t(O2-) showed different dependency on temperature and significantly affected the power density. Proton conduction dominated from 500 degrees C similar to 600 degrees C, and power density increased with increasing operating temperature due to improved proton conductivities. However, at 600 similar to 800 degrees C, proton conductivities decreased, which caused a decrease in power density. Further increase in temperature into the 800 degrees C similar to 900 degrees C range showed oxide ion conduction to then dominate, and the consequent improved oxide ion conductivity again increased the power density despite a decrease in open current voltage (OCV). (C) The Author(s) 2015. Published by ECS. All rights reserved.