98 research outputs found
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Nanoscale oxygen defect gradients in UO2+x surfaces.
Oxygen defects govern the behavior of a range of materials spanning catalysis, quantum computing, and nuclear energy. Understanding and controlling these defects is particularly important for the safe use, storage, and disposal of actinide oxides in the nuclear fuel cycle, since their oxidation state influences fuel lifetimes, stability, and the contamination of groundwater. However, poorly understood nanoscale fluctuations in these systems can lead to significant deviations from bulk oxidation behavior. Here we describe the use of aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy to resolve changes in the local oxygen defect environment in [Formula: see text] surfaces. We observe large image contrast and spectral changes that reflect the presence of sizable gradients in interstitial oxygen content at the nanoscale, which we quantify through first-principles calculations and image simulations. These findings reveal an unprecedented level of excess oxygen incorporated in a complex near-surface spatial distribution, offering additional insight into defect formation pathways and kinetics during [Formula: see text] surface oxidation
Thickness Dependent OER Electrocatalysis of Epitaxial LaFeO Thin Films
Transition metal oxides have long been an area of interest for water
electrocatalysis through the oxygen evolution and oxygen reduction reactions.
Iron oxides, such as LaFeO, are particularly promising due to the
favorable energy alignment of the valence and conduction bands comprised of
Fe cations and the visible light band gap of such materials. In this
work, we examine the role of band alignment on the electrocatalytic oxygen
evolution reaction (OER) in the intrinsic semiconductor LaFeO by growing
epitaxial films of varying thicknesses on Nb-doped SrTiO. Using cyclic
voltammetry and electrochemical impedance spectroscopy, we find that there is a
strong thickness dependence on the efficiency of electrocatalysis for OER.
These measurements are understood based on interfacial band alignment in the
system as confirmed by layer-resolved electron energy loss spectroscopy and
electrochemical Mott-Schottky measurements. Our results demonstrate the
importance of band engineering for the rational design of thin film
electrocatalysts for renewable energy sources.Comment: 19 pages, 6 figures; authors Burton and Paudel contributed equally;
supplement: 11 pages, 7 figure
Recommended from our members
Nanoscale oxygen defect gradients in UO<sub>2+x</sub> surfaces
Oxygen defects govern the behavior of a range of materials spanning catalysis, quantum computing, and nuclear energy. Understanding and controlling these defects is particularly important for the safe use, storage, and disposal of actinide oxides in the nuclear fuel cycle, since their oxidation state influences fuel lifetimes, stability, and the contamination of groundwater. However, poorly understood nanoscale fluctuations in these systems can lead to significant deviations from bulk oxidation behavior. Here we describe the use of aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy to resolve changes in the local oxygen defect environment in </p
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