Mixed Protonic-Electronic Conductivity of SrCe1−xPrxO3−δ

Abstract

Protonic conductors are gaining use in solid oxide fuel cells (SOFCs) and electrolysis cells (SOECs) as well as for H2 separation membranes. However, for SOFC/SOEC electrode and membrane applications their performance is limited by low electronic conductivity. One of the most promising classes of ceramic proton conductors, perovskites, have highly-tunable compositions allowing for the optimization of both ionic and electronic conductivity. In this work Pr-doped SrCeO3 was studied over a wide range of oxygen partial pressures (pO2’s) and temperatures to determine its defect properties and conductivity. Under reducing conditions Pr-doped SrCeO3 was found to be chemically and structurally stable, with an optimal Pr doping level of 10%. This composition shows greater conductivity compared to previously reported Eu-doped SrCeO3. Under low pO2 Pr-doped SrCeO3 exhibited n-type behavior as conductivity increased with decreasing pO2, suggesting that the electronic conductivity of SrCeO3 is significantly enhanced by Pr doping. Under high pO2 conditions, Pr-doped SrCeO3 exhibited p-type conductivity with higher conductivity in the presence of water affirming its protonic conductivity. This work validates the use of Pr as a means of enhancing electronic conductivity in proton conducting perovskites.