Atomic Scale Characterization of Defects on Oxide Surfaces

Abstract

The physics and chemistry of oxide surfaces cannot be recognized without taking into account the variety of lattice defects. Defects largely govern the electronic and optical properties of oxides, they offer potential binding sites for atoms and molecules, and serve as charge centers that control the donor or acceptor character of the material. In this contribution, we demonstrate how the nature of surface defects on oxides can be probed in an ensemble but also on the level of individual defects, focusing on defects on the surface of thin, single-crystalline oxide films of MgO and CeO₂ as prototype examples for non-reducible and reducible oxides, respectively. Scanning probe techniques play a fundamental role in this respect, as they enable direct visualization of surface defects and provide insight into the electronic structure of defects and local potential modulations in their vicinity

Design of Single-Atom Catalysts and Tracking Their Fate Using Operando and Advanced X-ray Spectroscopic Tools

“…Metal oxides, hydroxides, sulfides, and carbides are prominent classes of materials where single atoms of transition metals can be stabilized within their framework or on the surface at a defect site , which can arise from a cation, anion, or pair vacancy at different positions of the lattice as shown in Figure . These defect sites often provide binding possibilities for the extraneous atom, which occupies these vacancies and optimizes the energy of the system.…”

Ethanol-to-butadiene: the reaction and its catalysts

“…27 Model of structural defects on the surface of MgO. 258 Catalysis Science & Technology Mini review tricoordinated oxygen anions found in corner defects, rapidly deactivated under the poisoning effect of polycondensation products formed by their larger strength. 160,206 Many authors have noted that excessive basicity, both in terms of site quantity and strength, correlated with poorer catalytic performances.…”

“…255. Copyright 2016, American Chemical Society.Fig.27Model of structural defects on the surface of MgO 258.…”

Charge‐Promoted Self‐Metalation of Porphyrins on an Oxide Surface

“…[8, 9b] In contrast to this finding is the observation of selfmetalation of a complete 2H-TPP monolayer on MgO(001) thin films. [9a] While MgO thin film samples also exhibit a certain concentration of surface defects, [10] their limited abundance can, however, not explain the high degree of metalation occurring on the regular surface of the films, which remains a mystery. This calls for a different mechanism of the self-metalation reaction on the thin film surface that requires detailed knowledge and understanding of the morphology and electronic properties of the combined molecule-substrate system to be unraveled.…”