Oxygen Exchange Paper Published in Adv Mater Int
Understanding the behavior of oxygen in emerging solid oxide fuel cells and sensors is critical to achieve better performance and cycling behavior. In our latest study, led by Sandy Taylor, we utilize a unique in situ atom probe tomography approach to study dynamic oxygen exchange in Sr-doped lanthanum ferrite. Writing in Advanced Materials Interfaces, we use isotopically enriched 18O to track how oxygen diffusion is affected by structure, chemistry, and defects. This information will help us design better systems and devices that rely on oxygen exchange mechanisms.
From the abstract:
Perovskite structured transition metal oxides are important technological materials for catalysis and solid oxide fuel cell applications. Their functionality often depends on oxygen diffusivity and mobility through complex oxide heterostructures, which can be significantly impacted by structural and chemical modifications, such as doping. Further, when utilized within electrochemical cells, interfacial reactions with other components (e.g., Ni- and Cr-based alloy electrodes and interconnects) can influence the perovskite’s reactivity and ion transport, leading to complex dependencies that are difficult to control in real-world environments. Here we use isotopic tracers and atom probe tomography to directly visualize oxygen diffusion and transport pathways across perovskite and metal-perovskite heterostructures, i.e., (Ni-Cr coated) Sr-doped lanthanum ferrite (La0.5Sr0.5FeO3; LSFO). Annealing in 18O2(g) results in elemental and isotopic redistributions through oxygen exchange (OE) in the LSFO while Ni-Cr undergoes oxidation via multiple mechanisms and transport pathways. Complementary density functional theory calculations at experimental conditions provide rationale for OE reaction mechanisms and reveal a complex interplay of different thermodynamic and kinetic drivers. Our results shed light on the fundamental coupling of defects and oxygen transport in an important class of catalytic materials.
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