Ionic Conduction and Power Generation Characteristics of Pr-Doped Ba2In2O5 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 of PBI910 at 500°C was 0.81 and then decreased with increasing temperature, whereas the oxide ion transfer number was 0.07 and then increased with increasing temperature. Power generation experiments were evaluated at 500°C to 900°C using PBI as electrolyte and H2 as fuel. Results revealed that and showed different dependency on temperature and significantly affected the power density. Proton conduction dominated from 500°C∼600°C, and power density increased with increasing operating temperature due to improved proton conductivities. However, at 600∼800°C, proton conductivities decreased, which caused a decrease in power density. Further increase in temperature into the 800°C∼900°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).