BaFeO3-Δ-Based Materials for Intermediate-Temperature Solid Oxide Fuel Cells and Beyond

Abstract

Energy conversion and storage is a central problem to modern society, requiring the deployment of novel “green” technologies. Solid oxide fuel cells (SOFCs) are very promising because they can convert chemical energy directly to electricity with efficiencies as high as 60%. However, one of the bottlenecks of this technology is the limited activity of typical cathode materials. In this presentation, we will overview doped-BaFeO3-δ (BFO) as a potential high-activity SOFC cathode material. We first fabricate Ba0.95La0.05FeO3-δ (BLF) single crystal thin films by pulsed laser deposition (PLD) on yttria-stabilized zirconia (YSZ) substrates. The phase structure, surface morphology and roughness of the BLF thin films are characterized by X-ray diffraction and atomic force microscopy. X-ray photoelectron spectroscopy is used to analyze the elemental composition and chemical state of the deposited thin film [1-2]. Electrochemical impedance spectra measurements obtained from the symmetric cells with the configuration of BLF /SDC/YSZ/SDC/ BLF reveal that polarization resistance of BLF (001) thin films (100 nm) is as low as ~0.1 Ω cm2 at 700 °C and 0.21 atm oxygen pressure. The polarization resistances of BLF are lower than those of other perovskite electrodes. Furthermore, our computational results, including density functional theory and molecular dynamics simulations, show that the BLF has a low vacancy formation energy and fast oxygen transport [3-4]. The effect of various A- and B-site substitutions on the BFO’s activity from both an experimental [5, 6] and computational [7] perspective are then explored. Finally, opportunities to develop ferrites are discussed together with their use as low temperature electrocatalysts. Acknowledgements The authors gratefully acknowledge the Research Grants Council of Hong Kong for support through the project 16207615 and 16227016.