Resolving diverse oxygen transport pathways across Sr-doped lanthanum ferrite and metal-perovskite heterostructures

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 (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 (DFT) 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.Comment: 39 pages, 10 figure

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Item does not contain fulltext14 augustus 201

Functional traits as indicators of biodiversity response to land use changes across ecosystems and organisms

Rigorous and widely applicable indicators of biodiversity are needed to monitor the responses of ecosystems to global change and design effective conservation schemes. Among the potential indicators of biodiversity, those based on the functional traits of species and communities are interesting because they can be generalized to similar habitats and can be assessed by relatively rapid field assessment across eco-regions. Functional traits, however, have as yet been rarely considered in current common monitoring schemes. Moreover, standardized procedures of trait measurement and analyses have almost exclusively been developed for plants but different approaches have been used for different groups of organisms. Here we review approaches using functional traits as biodiversity indicators focussing not on plants as usual but particularly on animal groups that are commonly considered in different biodiversity monitoring schemes (benthic invertebrates, collembolans, above ground insects and birds). Further, we introduce a new framework based on functional traits indices and illustrate it using case studies where the traits of these organisms can help monitoring the response of biodiversity to different land use change drivers. We propose and test standard procedures to integrate different components of functional traits into biodiversity monitoring schemes across trophic levels and disciplines. We suggest that the development of indicators using functional traits could complement, rather than replace, the existent biodiversity monitoring. In this way, the comparison of the effect of land use changes on biodiversity is facilitated and is expected to positively influence conservation management practices