Surface structure and reactivity of
multi-component oxides at the atomic scale

@article{Franceschi2020,

title = {Atomically resolved surface phases of La_{0.8}Sr_{0.2}MnO_{3}(110) thin films},

author = {Giada Franceschi and Michael Schmid and Ulrike Diebold and Michele Riva},

doi = {10.1039/d0ta07032g},

year  = {2020},

date = {2020-09-04},

urldate = {2020-09-04},

journal = {Journal of Materials Chemistry A},

volume = {8},

number = {43},

pages = {22947--22961},

publisher = {Royal Society of Chemistry (RSC)},

abstract = {The atomic-scale properties of lanthanum–strontium manganite (La_{1-x}Sr_{x}MnO_{3−δ}, LSMO) surfaces are of high interest because of the roles of the material as a prototypical complex oxide, in the fabrication of spintronic devices and in catalytic applications. This work combines pulsed laser deposition (PLD) with atomically resolved scanning tunneling microscopy (STM) and surface analysis techniques (low-energy electron diffraction – LEED, X-ray photoelectron spectroscopy – XPS, and low-energy He^{+} ion scattering – LEIS) to assess the atomic properties of La_{0.8}Sr_{0.2}MnO_{3}(110) surfaces and their dependence on the surface composition. Epitaxial films with 130 nm thickness were grown on Nb-doped SrTiO_{3}(110) and their near-surface stoichiometry was adjusted by depositing La and Mn in sub-monolayer amounts, quantified with a movable quartz-crystal microbalance. The resulting surfaces were equilibrated at 700 °C under 0.2 mbar O_{2}, i.e., under conditions that bridge the gap between ultra-high vacuum and the operating conditions of high-temperature solid-oxide fuel cells, where LSMO is used as the cathode. The atomic details of various composition-related surface phases have been unveiled. The phases are characterized by distinct structural and electronic properties and vary in their ability to ccommodate deposited cations.},

keywords = {P02, pre-TACO},

pubstate = {published},

tppubtype = {article}

}

@article{Grumelli2020,

title = {Electrochemical Stability of the Reconstructed Fe_{3}O_{4}(001) Surface},

author = {Doris Grumelli and Tim Wiegmann and Sara Barja and Finn Reikowski and Fouad Maroun and Philippe Allongue and Jan Balajka and Gareth S Parkinson and Ulrike Diebold and Klaus Kern and Olaf M Magnussen},

doi = {10.1002/anie.202008785},

year  = {2020},

date = {2020-07-29},

journal = {Angewandte Chemie - International Edition},

volume = {59},

number = {49},

pages = {21904--21908},

publisher = {Wiley},

abstract = {Establishing the atomic-scale structure of metal-oxide surfaces during electrochemical reactions is a key step to modeling this important class of electrocatalysts. Here, we demonstrate that the characteristic (√2×√2)R45° surface reconstruction formed on (001)-oriented magnetite single crystals is maintained after immersion in 0.1 M NaOH at 0.20 V vs. Ag/AgCl and we investigate its dependence on the electrode potential. We follow the evolution of the surface using in situ and operando surface X-ray diffraction from the onset of hydrogen evolution, to potentials deep in the oxygen evolution reaction (OER) regime. The reconstruction remains stable for hours between −0.20 and 0.60 V and, surprisingly, is still present at anodic current densities of up to 10 mA cm^{−2} and strongly affects the OER kinetics. We attribute this to a stabilization of the Fe_{3}O_{4} bulk by the reconstructed surface. At more negative potentials, a gradual and largely irreversible lifting of the reconstruction is observed due to the onset of oxide reduction.},

keywords = {P02, P04, pre-TACO},

pubstate = {published},

tppubtype = {article}

}

@article{Jakub2019,

title = {Local Structure and Coordination Define Adsorption in a Model Ir_{1}/Fe_{3}O_{4} Single-Atom Catalyst},

author = {Zdenek Jakub and Jan Hulva and Matthias Meier and Roland Bliem and Florian Kraushofer and Martin Setvin and Michael Schmid and Ulrike Diebold and Cesare Franchini and Gareth S Parkinson},

doi = {10.1002/anie.201907536},

year  = {2019},

date = {2019-07-24},

urldate = {2019-07-24},

journal = {Angewandte Chemie - International Edition},

volume = {58},

number = {39},

pages = {13961--13968},

publisher = {Wiley},

abstract = {Single-atom catalysts (SACs) bridge homo- and heterogeneous catalysis because the active site is a metal atom coordinated to surface ligands. The local binding environment of the atom should thus strongly influence how reactants adsorb. Now, atomically resolved scanning-probe microscopy, X-ray photoelectron spectroscopy, temperature-programmed desorption, and DFT are used to study how CO binds at different Ir_{1} sites on a precisely defined Fe_{3}O_{4}(001) support. The two- and five-fold-coordinated Ir adatoms bind CO more strongly than metallic Ir, and adopt structures consistent with square-planar Ir^{I} and octahedral Ir^{III} complexes, respectively. Ir incorporates into the subsurface already at 450 K, becoming inactive for adsorption. Above 900 K, the Ir adatoms agglomerate to form nanoparticles encapsulated by iron oxide. These results demonstrate the link between SAC systems and coordination complexes, and that incorporation into the support is an important deactivation mechanism.},

keywords = {P02, P04, P07, pre-TACO},

pubstate = {published},

tppubtype = {article}

}

@article{Diebold2019,

title = {Preface: Surface Science of functional oxides},

author = {Ulrike Diebold and Günther Rupprechter},

doi = {10.1016/j.susc.2018.11.017},

year  = {2019},

date = {2019-03-01},

journal = {Surface Science},

volume = {681},

pages = {A1},

publisher = {Elsevier BV},

keywords = {P02, P08, pre-TACO},

pubstate = {published},

tppubtype = {article}

}

@article{Reticcioli2019,

title = {Interplay between Adsorbates and Polarons: CO on Rutile TiO_{2}(110)},

author = {Michele Reticcioli and Igor Sokolović and Michael Schmid and Ulrike Diebold and Martin Setvin and Cesare Franchini},

doi = {10.1103/physrevlett.122.016805},

year  = {2019},

date = {2019-01-09},

journal = {Physical Review Letters},

volume = {122},

number = {1},

pages = {016805},

publisher = {American Physical Society (APS)},

abstract = {Polaron formation plays a major role in determining the structural, electrical, and chemical properties of ionic crystals. Using a combination of first-principles calculations, scanning tunneling microscopy, and atomic force microscopy, we analyze the interaction of polarons with CO molecules adsorbed on the reduced rutile TiO_{2}(110) surface. Adsorbed CO shows attractive coupling with polarons in the surface layer, and repulsive interaction with polarons in the subsurface layer. As a result, CO adsorption depends on the reduction state of the sample. For slightly reduced surfaces, many adsorption configurations with comparable adsorption energies exist and polarons reside in the subsurface layer. At strongly reduced surfaces, two adsorption configurations dominate: either inside an oxygen vacancy, or at surface Ti_{5c} sites, coupled with a surface polaron. Similar conclusions are predicted for TiO_{2}(110) surfaces containing near-surface Ti interstitials. These results show that polarons are of primary importance for understanding the performance of polar semiconductors and transition metal oxides in catalysis and energy-related applications.},

keywords = {P02, P07, pre-TACO},

pubstate = {published},

tppubtype = {article}

}

@article{Reticcioli2017,

title = {Polaron-Driven Surface Reconstructions},

author = {Michele Reticcioli and Martin Setvin and Xianfeng Hao and Peter Flauger and Georg Kresse and Michael Schmid and Ulrike Diebold and Cesare Franchini},

doi = {10.1103/physrevx.7.031053},

year  = {2017},

date = {2017-09-25},

urldate = {2017-09-25},

journal = {Physical Review X},

volume = {7},

number = {3},

pages = {031053},

publisher = {American Physical Society (APS)},

abstract = {Geometric and electronic surface reconstructions determine the physical and chemical properties of surfaces and, consequently, their functionality in applications. The reconstruction of a surface minimizes its surface free energy in otherwise thermodynamically unstable situations, typically caused by dangling bonds, lattice stress, or a divergent surface potential, and it is achieved by a cooperative modification of the atomic and electronic structure. Here, we combined first-principles calculations and surface techniques (scanning tunneling microscopy, non-contact atomic force microscopy, scanning tunneling spectroscopy) to report that the repulsion between negatively charged polaronic quasiparticles, formed by the interaction between excess electrons and the lattice phonon field, plays a key role in surface reconstructions. As a paradigmatic example, we explain the (1×1) to (1×2) transition in rutile TiO_{2}(110).},

keywords = {P02, P03, P07, pre-TACO},

pubstate = {published},

tppubtype = {article}

}