1
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Noordhoek K, Bartel CJ. Accelerating the prediction of inorganic surfaces with machine learning interatomic potentials. NANOSCALE 2024. [PMID: 38470833 DOI: 10.1039/d3nr06468a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/14/2024]
Abstract
The surface properties of solid-state materials often dictate their functionality, especially for applications where nanoscale effects become important. The relevant surface(s) and their properties are determined, in large part, by the material's synthesis or operating conditions. These conditions dictate thermodynamic driving forces and kinetic rates responsible for yielding the observed surface structure and morphology. Computational surface science methods have long been applied to connect thermochemical conditions to surface phase stability, particularly in the heterogeneous catalysis and thin film growth communities. This review provides a brief introduction to first-principles approaches to compute surface phase diagrams before introducing emerging data-driven approaches. The remainder of the review focuses on the application of machine learning, predominantly in the form of learned interatomic potentials, to study complex surfaces. As machine learning algorithms and large datasets on which to train them become more commonplace in materials science, computational methods are poised to become even more predictive and powerful for modeling the complexities of inorganic surfaces at the nanoscale.
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Affiliation(s)
- Kyle Noordhoek
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN, 55455, USA.
| | - Christopher J Bartel
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN, 55455, USA.
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2
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Tong H, Hu W, Fu M, Yang C, Tao Z. Nickel-Regulated Composite Cathode with Balanced Triple Conductivity for Proton-Conducting Solid Oxide Fuel Cells. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2304555. [PMID: 37897316 PMCID: PMC10754136 DOI: 10.1002/advs.202304555] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Revised: 09/13/2023] [Indexed: 10/30/2023]
Abstract
Proton-conducting solid oxide fuel cells (H-SOFCs) have the potential to be a promising technology for energy conversion and storage. To achieve high chemical compatibility and catalytic activity, nickel-doped barium ferrate with triple conducting ability is developed as cathodes for H-SOFCs, presenting an impressive electrochemical performance at intermediate temperatures. The cell performance with the optimized BaCe0.26 Ni0.1 Fe0.64 O3 -δ (BCNF10) composite cathode reaches an outstanding performance of 1.04 W cm-2 at 600 °C. The high electrocatalytic capacity of the nickel-doped barium ferrate cathode can be attributed to its significant proton conductivity which is confirmed through hydrogen permeation experiments. Density functional theory (DFT) calculations are further conducted to reveal that the presence of nickel can enhance processes of hydration formation and proton migration, leading to improve proton conductivity and electro-catalytic activity.
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Affiliation(s)
- Hua Tong
- School of Resources, Environment and Safety EngineeringUniversity of South ChinaHengyangHunan421001China
| | - Wenjing Hu
- School of Resources, Environment and Safety EngineeringUniversity of South ChinaHengyangHunan421001China
| | - Min Fu
- School of Resources, Environment and Safety EngineeringUniversity of South ChinaHengyangHunan421001China
| | - Chunli Yang
- College of Materials Science and EngineeringXi'an University of Architecture and TechnologyXi'an710043China
| | - Zetian Tao
- School of Resources, Environment and Safety EngineeringUniversity of South ChinaHengyangHunan421001China
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3
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Fung V, Hu G, Wu Z, Jiang DE. Hydrogen-mediated polarity compensation on the (110) surface terminations of ABO3 perovskites. J Chem Phys 2023; 159:174706. [PMID: 37929866 DOI: 10.1063/5.0161435] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2023] [Accepted: 10/17/2023] [Indexed: 11/07/2023] Open
Abstract
Polar surfaces undergo polarity compensation, which can lead to significantly different surface chemistry from their nonpolar counterparts. This process in turn can substantially alter the binding of adsorbates on the surface. Here, we find that hydrogen binds much more strongly to the polar (110) surface than the nonpolar (100) surface for a wide range of ABO3 perovskites, forming a hydroxyl layer on the O24- termination and a hydride layer on the ABO4+ termination of the (110) surface. The stronger adsorption on the polar surfaces can be explained by polarity compensation: hydrogen atoms can act as electron donors or acceptors to compensate for the polarity of perovskite surfaces. The relative stability of the surface terminations is further compared under different gas environments and several perovskites have been found to form stable surface hydride layers under oxygen-poor conditions. These results demonstrate the feasibility of creating stable surface hydrides on perovskites by polarity compensation which might lead to new hydrogenation catalysts based on ABO3 perovskites.
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Affiliation(s)
- Victor Fung
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Guoxiang Hu
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Zili Wu
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - De-En Jiang
- Department of Chemistry, University of California, Riverside, California 92521, USA
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee 37235, USA
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4
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Wang Z, Byun J, Wang Z, Xing Y, Seo J, Lee J, Oh SH. Direct Observation of Atomic Step-Assisted Stabilization of Polar Surfaces. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2303051. [PMID: 37358063 DOI: 10.1002/adma.202303051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2023] [Revised: 06/11/2023] [Indexed: 06/27/2023]
Abstract
Polar surfaces are intrinsically unstable and thus highly reactive due to the uncompensated surface charges. The charge compensation is accompanied by various surface reconstructions, establishing novel functionality for their applications. The present in situ atomic-scale electron microscopy study directly shows that the atomic step and step-assisted reconstruction play central roles in the charge compensation of polar oxide surfaces. The flat (LaO)+ -terminated LaAlO3 (001) polar surface, when annealed at high temperature in vacuum, transits to the (015) vicinal surface via the dynamic motion and interaction of atomic steps. While the (015) vicinal surface possesses zero polarization along the surface normal, a thermodynamic ground state is achieved when the in-plane polarization is fully compensated via the reconstruction of step-edge atoms; the step-edge La atoms are displaced from their ordinary atomic sites toward the adjacent Al step-edge sites, resulting in the formation of negatively charged La vacancies at the corresponding step edges. As confirmed by first-principles calculations, the observed step reconstruction of (015) vicinal surface can completely cancel both out-of-plane and in-plane electric fields. This hitherto unknown mechanism reveals the central role of step reconstruction in stabilizing a polar surface, providing valuable insights for understanding the novel charge compensation mechanism accompanied by the step reconstruction.
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Affiliation(s)
- Zhipeng Wang
- Department of Energy Science, Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | - Jinho Byun
- Department of Physics, Pusan National University, Busan, 46241, Republic of Korea
- Department of Energy Engineering, Institute for Energy Materials and Devices, Korea Institute of Energy Technology (KENTECH), Naju, 58330, Republic of Korea
| | - Zhen Wang
- Department of Energy Science, Sungkyunkwan University, Suwon, 16419, Republic of Korea
- Department of Energy Engineering, Institute for Energy Materials and Devices, Korea Institute of Energy Technology (KENTECH), Naju, 58330, Republic of Korea
| | - Yaolong Xing
- Department of Energy Science, Sungkyunkwan University, Suwon, 16419, Republic of Korea
- Department of Energy Engineering, Institute for Energy Materials and Devices, Korea Institute of Energy Technology (KENTECH), Naju, 58330, Republic of Korea
| | - Jinsol Seo
- Department of Energy Science, Sungkyunkwan University, Suwon, 16419, Republic of Korea
- Department of Energy Engineering, Institute for Energy Materials and Devices, Korea Institute of Energy Technology (KENTECH), Naju, 58330, Republic of Korea
| | - Jaekwang Lee
- Department of Physics, Pusan National University, Busan, 46241, Republic of Korea
| | - Sang Ho Oh
- Department of Energy Science, Sungkyunkwan University, Suwon, 16419, Republic of Korea
- Department of Energy Engineering, Institute for Energy Materials and Devices, Korea Institute of Energy Technology (KENTECH), Naju, 58330, Republic of Korea
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5
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Siebenhofer M, Riedl C, Nenning A, Raznjevic S, Fellner F, Artner W, Zhang Z, Rameshan C, Fleig J, Kubicek M. Crystal-Orientation-Dependent Oxygen Exchange Kinetics on Mixed Conducting Thin-Film Surfaces Investigated by In Situ Studies. ACS APPLIED ENERGY MATERIALS 2023; 6:6712-6720. [PMID: 37388294 PMCID: PMC10301866 DOI: 10.1021/acsaem.3c00870] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Accepted: 05/25/2023] [Indexed: 07/01/2023]
Abstract
The oxygen exchange kinetics and the surface chemistry of epitaxially grown, dense La0.6Sr0.4CoO3-δ (LSC) thin films in three different orientations, (001), (110), and (111), were investigated by means of in situ impedance spectroscopy during pulsed laser deposition (i-PLD) and near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS). i-PLD measurements showed that pristine LSC surfaces exhibit very fast surface exchange kinetics but revealed no significant differences between the specific orientations. However, as soon as the surfaces were in contact with acidic, gaseous impurities, such as S-containing compounds in nominally pure measurement atmospheres, NAP-XPS measurements revealed that the (001) orientation is substantially more susceptible to the formation of sulfate adsorbates and a concomitant performance decrease. This result is further substantiated by a stronger increase of the work function on (001)-oriented LSC surfaces upon sulfate adsorbate formation and by a faster performance degradation of these surfaces in ex situ measurement setups. This phenomenon has potentially gone unnoticed in the discussion of the interplay between the crystal orientation and the oxygen exchange kinetics and might have far-reaching implications for real solid oxide cell electrodes, where porous materials exhibit a wide variety of differently oriented and reconstructed surfaces.
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Affiliation(s)
- Matthäus Siebenhofer
- Institute
of Chemical Technologies and Analytics, Vienna University of Technology, Vienna 1060, Austria
- Centre
for Electrochemistry and Surface Technology (CEST), Wiener Neustadt 2700, Austria
| | - Christoph Riedl
- Institute
of Chemical Technologies and Analytics, Vienna University of Technology, Vienna 1060, Austria
| | - Andreas Nenning
- Institute
of Chemical Technologies and Analytics, Vienna University of Technology, Vienna 1060, Austria
| | - Sergej Raznjevic
- Erich
Schmid Institute of Materials Science, Austrian
Academy of Sciences, Leoben 8700, Austria
| | - Felix Fellner
- Institute
of Chemical Technologies and Analytics, Vienna University of Technology, Vienna 1060, Austria
| | - Werner Artner
- X-Ray
Center, Vienna University of Technology, Vienna 1060, Austria
| | - Zaoli Zhang
- Erich
Schmid Institute of Materials Science, Austrian
Academy of Sciences, Leoben 8700, Austria
| | - Christoph Rameshan
- Chair
of Physical Chemistry, Montanuniversität
Leoben, Leoben 8700, Austria
| | - Jürgen Fleig
- Institute
of Chemical Technologies and Analytics, Vienna University of Technology, Vienna 1060, Austria
| | - Markus Kubicek
- Institute
of Chemical Technologies and Analytics, Vienna University of Technology, Vienna 1060, Austria
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6
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Riedl C, Siebenhofer M, Ražnjević S, Bumberger AE, Zhang Z, Limbeck A, Opitz AK, Kubicek M, Fleig J. In situ electrochemical observation of anisotropic lattice contraction of La 0.6Sr 0.4FeO 3-δ electrodes during pulsed laser deposition. Phys Chem Chem Phys 2022; 25:142-153. [PMID: 36476841 PMCID: PMC9768847 DOI: 10.1039/d2cp04977e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
La0.6Sr0.4FeO3-δ (LSF) electrodes were grown on different electrolyte substrates by pulsed laser deposition (PLD) and their oxygen exchange reaction (OER) resistance was tracked in real-time by in situ PLD impedance spectroscopy (i-PLD) inside the PLD chamber. This enables measurements on pristine surfaces free from any contaminations and the direct observation of thickness dependent properties. As substrates, yttria-stabilized zirconia single crystals (YSZ) were used for polycrystalline LSF growth and La0.95Sr0.05Ga0.95Mg0.05O3-δ (LSGM) single crystals or YSZ single crystals with a 5 nm buffer-layer of Gd0.2Ce0.8O2-δ for epitaxial LSF film growth. While polycrystalline LSF electrodes show a constant OER resistance in a broad thickness range, epitaxially grown LSF electrodes exhibit a continuous and strong increase of the OER resistance with film thickness until ≈60 nm. In addition, the activation energy of the OER resistance increases by 0.23 eV compared to polycrystalline LSF. High resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) measurements reveal an increasing contraction of the out-of-plane lattice parameter in the epitaxial LSF electrodes over electrode thickness. Defect thermodynamic simulations suggest that the decrease of the LSF unit cell volume is accompanied by a lowering of the oxygen vacancy concentration, explaining both the resistive increase and the increased activation energy.
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Affiliation(s)
- Christoph Riedl
- Institute of Chemical Technologies and Analytics, TU WienViennaAustria
| | - Matthäus Siebenhofer
- Institute of Chemical Technologies and Analytics, TU WienViennaAustria,Centre for Electrochemistry and Surface Technology, CEST, WrNeustadtAustria
| | | | | | - Zaoli Zhang
- Erich Schmid Institute for Materials ScienceLeobenAustria
| | - Andreas Limbeck
- Institute of Chemical Technologies and Analytics, TU WienViennaAustria
| | | | - Markus Kubicek
- Institute of Chemical Technologies and Analytics, TU WienViennaAustria
| | - Jürgen Fleig
- Institute of Chemical Technologies and Analytics, TU WienViennaAustria
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7
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Wang J, Kumar A, Wardini JL, Zhang Z, Zhou H, Crumlin EJ, Sadowski JT, Woller KB, Bowman WJ, LeBeau JM, Yildiz B. Exsolution-Driven Surface Transformation in the Host Oxide. NANO LETTERS 2022; 22:5401-5408. [PMID: 35771744 DOI: 10.1021/acs.nanolett.2c01439] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Exsolution synthesizes self-assembled metal nanoparticle catalysts via phase precipitation. An overlooked aspect in this method thus far is how exsolution affects the host oxide surface chemistry and structure. Such information is critical as the oxide itself can also contribute to the overall catalytic activity. Combining X-ray and electron probes, we investigated the surface transformation of thin-film SrTi0.65Fe0.35O3 during Fe0 exsolution. We found that exsolution generates a highly Fe-deficient near-surface layer of about 2 nm thick. Moreover, the originally single-crystalline oxide near-surface region became partially polycrystalline after exsolution. Such drastic transformations at the surface of the oxide are important because the exsolution-induced nonstoichiometry and grain boundaries can alter the oxide ion transport and oxygen exchange kinetics and, hence, the catalytic activity toward water splitting or hydrogen oxidation reactions. These findings highlight the need to consider the exsolved oxide surface, in addition to the metal nanoparticles, in designing the exsolved nanocatalysts.
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Affiliation(s)
- Jiayue Wang
- Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Abinash Kumar
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Jenna L Wardini
- Department of Materials Science & Engineering, University of California, Irvine, California 92697, United States
| | - Zhan Zhang
- Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Hua Zhou
- Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Ethan J Crumlin
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Jerzy T Sadowski
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - Kevin B Woller
- Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - William J Bowman
- Department of Materials Science & Engineering, University of California, Irvine, California 92697, United States
| | - James M LeBeau
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Bilge Yildiz
- Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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8
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Zhao T, Zhao J, Tao X, Yu H, Li M, Zeng J, Wang H. Highly active and thermostable submonolayer La(NiCo)O Δ catalyst stabilized by a perovskite LaCrO 3 support. Commun Chem 2022; 5:70. [PMID: 36697603 PMCID: PMC9814614 DOI: 10.1038/s42004-022-00686-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Accepted: 05/13/2022] [Indexed: 01/28/2023] Open
Abstract
It is important to develop highly active and stable catalysts for high temperature reactions, such as dry reforming of methane. Here we show a La(NiCo)OΔ (LNCO) submonolayer catalyst (SMLC) stabilized by the surface lattice of a perovskite LaCrO3 support and demonstrate a Ni-Co synergistic effect. The submonolayer/support type catalyst was prepared by in-situ hydrogen reduction of a LaNi0.05Co0.05Cr0.9O3 precursor synthesized by a sol-gel method. The LNCO-SMLC is highly active and very stable during a 100 h on stream test at 750 °C under the reaction conditions of dry reforming of methane. The catalyst also shows good anti-coking ability. We found that the synergistic effect between Ni and Co atoms in LNCO-SMLC remarkably improved the thermostability of the catalyst. This work provides a useful concept for designing atomically dispersed catalysts with high thermostability.
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Affiliation(s)
- Tingting Zhao
- grid.59053.3a0000000121679639Hefei National Laboratory for Physical Science at the Microscale, University of Science and Technology of China, 230026 Hefei, Anhui People’s Republic of China
| | - Jiankang Zhao
- grid.59053.3a0000000121679639Hefei National Laboratory for Physical Science at the Microscale, University of Science and Technology of China, 230026 Hefei, Anhui People’s Republic of China
| | - Xuyingnan Tao
- grid.59053.3a0000000121679639Hefei National Laboratory for Physical Science at the Microscale, University of Science and Technology of China, 230026 Hefei, Anhui People’s Republic of China
| | - Haoran Yu
- grid.59053.3a0000000121679639Hefei National Laboratory for Physical Science at the Microscale, University of Science and Technology of China, 230026 Hefei, Anhui People’s Republic of China
| | - Ming Li
- grid.59053.3a0000000121679639Hefei National Laboratory for Physical Science at the Microscale, University of Science and Technology of China, 230026 Hefei, Anhui People’s Republic of China
| | - Jie Zeng
- grid.59053.3a0000000121679639Hefei National Laboratory for Physical Science at the Microscale, University of Science and Technology of China, 230026 Hefei, Anhui People’s Republic of China
| | - Haiqian Wang
- grid.59053.3a0000000121679639Hefei National Laboratory for Physical Science at the Microscale, University of Science and Technology of China, 230026 Hefei, Anhui People’s Republic of China
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9
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Riedl C, Siebenhofer M, Nenning A, Friedbacher G, Weiss M, Rameshan C, Bernardi J, Limbeck A, Kubicek M, Opitz AK, Fleig J. Performance modulation through selective, homogenous surface doping of lanthanum strontium ferrite electrodes revealed by in situ PLD impedance measurements. JOURNAL OF MATERIALS CHEMISTRY. A 2022; 10:2973-2986. [PMID: 35223041 PMCID: PMC8823903 DOI: 10.1039/d1ta08634k] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Accepted: 12/03/2021] [Indexed: 06/14/2023]
Abstract
Accelerating the oxygen reduction kinetics of solid oxide fuel cell (SOFC) cathodes is crucial to improve their efficiency and thus to provide the basis for an economically feasible application of intermediate temperature SOFCs. In this work, minor amounts of Pt were doped into lanthanum strontium ferrite (LSF) thin film electrodes to modulate the material's oxygen exchange performance. Surprisingly, Pt was found to be incorporated on the B-site of the perovskite electrode as non metallic Pt4+. The polarization resistance of LSF thin film electrodes with and without additional Pt surface doping was compared directly after film growth employing in situ electrochemical impedance spectroscopy inside a PLD chamber (i-PLD). This technique enables observation of the polarization resistance of pristine electrodes unaltered by degradation or any external contamination of the electrode surface. Moreover, growth of multi-layers of materials with different compositions on the very same single crystalline electrolyte substrate combined with in situ impedance measurements allow excellent comparability of different materials. Even a 5 nm layer of Pt doped LSF (1.5 at% Pt), i.e. a Pt loading of 80 ng cm-2, improved the polarization resistance by a factor of about 2.5. In addition, p(O2) and temperature dependent impedance measurements on both pure and Pt doped LSF were performed in situ and obtained similar activation energies and p(O2) dependence of the polarization resistance, which allow us to make far reaching mechanistic conclusions indicating that Pt4+ introduces additional active sites.
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Affiliation(s)
- Christoph Riedl
- Institute of Chemical Technologies and Analytics, TU Wien Getreidemarkt 9-E164 1060 Vienna Austria
| | - Matthäus Siebenhofer
- Institute of Chemical Technologies and Analytics, TU Wien Getreidemarkt 9-E164 1060 Vienna Austria
- CEST Kompetenzzentrum für elektrochemische Oberflächentechnologie GmbH TFZ - Wiener Neustadt Viktor-Kaplan-Strasse 2 2700 Wiener Neustadt Austria
| | - Andreas Nenning
- Institute of Chemical Technologies and Analytics, TU Wien Getreidemarkt 9-E164 1060 Vienna Austria
| | - Gernot Friedbacher
- Institute of Chemical Technologies and Analytics, TU Wien Getreidemarkt 9-E164 1060 Vienna Austria
| | - Maximilian Weiss
- Institute of Chemical Technologies and Analytics, TU Wien Getreidemarkt 9-E164 1060 Vienna Austria
| | - Christoph Rameshan
- Institute of Materials Chemistry, TU Wien Getreidemarkt 9-E165-PC 1060 Vienna Austria
| | - Johannes Bernardi
- USTEM Universitäre Service-Einrichtung für Transmissions-Elektronenmikroskopie, TU Wien Wiedner Hauptstrasse. 8-10 1040 Wien Austria
| | - Andreas Limbeck
- Institute of Chemical Technologies and Analytics, TU Wien Getreidemarkt 9-E164 1060 Vienna Austria
| | - Markus Kubicek
- Institute of Chemical Technologies and Analytics, TU Wien Getreidemarkt 9-E164 1060 Vienna Austria
| | - Alexander Karl Opitz
- Institute of Chemical Technologies and Analytics, TU Wien Getreidemarkt 9-E164 1060 Vienna Austria
| | - Juergen Fleig
- Institute of Chemical Technologies and Analytics, TU Wien Getreidemarkt 9-E164 1060 Vienna Austria
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10
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Wanzenböck R, Arrigoni M, Bichelmaier S, Buchner F, Carrete J, Madsen GKH. Neural-network-backed evolutionary search for SrTiO 3(110) surface reconstructions. DIGITAL DISCOVERY 2022; 1:703-710. [PMID: 36324606 PMCID: PMC9549766 DOI: 10.1039/d2dd00072e] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Accepted: 08/23/2022] [Indexed: 12/03/2022]
Abstract
The determination of atomic structures in surface reconstructions has typically relied on structural models derived from intuition and domain knowledge. Evolutionary algorithms have emerged as powerful tools for such structure searches. However, when density functional theory is used to evaluate the energy the computational cost of a thorough exploration of the potential energy landscape is prohibitive. Here, we drive the exploration of the rich phase diagram of TiOx overlayer structures on SrTiO3(110) by combining the covariance matrix adaptation evolution strategy (CMA-ES) and a neural-network force field (NNFF) as a surrogate energy model. By training solely on SrTiO3(110) 4×1 overlayer structures and performing CMA-ES runs on 3×1, 4×1 and 5×1 overlayers, we verify the transferability of the NNFF. The speedup due to the surrogate model allows taking advantage of the stochastic nature of the CMA-ES to perform exhaustive sets of explorations and identify both known and new low-energy reconstructions. The covariance matrix adaptation evolution strategy (CMA-ES) and a fully automatically differentiable, transferable neural-network force field are combined to explore TiOx overlayer structures on SrTiO3(110) 3×1, 4×1 and 5×1 surfaces.![]()
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Affiliation(s)
- Ralf Wanzenböck
- Institute of Materials Chemistry, TU Wien, 1060 Vienna, Austria
| | - Marco Arrigoni
- Institute of Materials Chemistry, TU Wien, 1060 Vienna, Austria
| | | | - Florian Buchner
- Institute of Materials Chemistry, TU Wien, 1060 Vienna, Austria
| | - Jesús Carrete
- Institute of Materials Chemistry, TU Wien, 1060 Vienna, Austria
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11
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Su S, Siretanu I, van den Ende D, Mei B, Mul G, Mugele F. Facet-Dependent Surface Charge and Hydration of Semiconducting Nanoparticles at Variable pH. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2106229. [PMID: 34609757 DOI: 10.1002/adma.202106229] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Revised: 09/14/2021] [Indexed: 06/13/2023]
Abstract
Understanding structure and function of solid-liquid interfaces is essential for the development of nanomaterials for various applications including heterogeneous catalysis in liquid phase processes and water splitting for storage of renewable electricity. The characteristic anisotropy of crystalline nanoparticles is believed to be essential for their performance but remains poorly understood and difficult to characterize. Dual scale atomic force microscopy is used to measure electrostatic and hydration forces of faceted semiconducting SrTiO3 nanoparticles in aqueous electrolyte at variable pH. The following are demonstrated: the ability to quantify strongly facet-dependent surface charges yielding isoelectric points of the dominant {100} and {110} facets that differ by as much as 2 pH units; facet-dependent accumulation of oppositely charged (SiO2 ) particles; and that atomic scale defects can be resolved but are in fact rare for the samples investigated. Atomically resolved images and facet-dependent oscillatory hydration forces suggest a microscopic charge generation mechanism that explains colloidal scale electrostatic forces.
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Affiliation(s)
- Shaoqiang Su
- Physics of Complex Fluids Group and MESA+ Institute, Faculty of Science and Technology, University of Twente, P.O. Box 217, Enschede, 7500 AE, The Netherlands
| | - Igor Siretanu
- Physics of Complex Fluids Group and MESA+ Institute, Faculty of Science and Technology, University of Twente, P.O. Box 217, Enschede, 7500 AE, The Netherlands
| | - Dirk van den Ende
- Physics of Complex Fluids Group and MESA+ Institute, Faculty of Science and Technology, University of Twente, P.O. Box 217, Enschede, 7500 AE, The Netherlands
| | - Bastian Mei
- Photocatalytic Synthesis Group and MESA+ Institute, Faculty of Science and Technology, University of Twente, P.O. Box 217, Enschede, 7500 AE, The Netherlands
| | - Guido Mul
- Photocatalytic Synthesis Group and MESA+ Institute, Faculty of Science and Technology, University of Twente, P.O. Box 217, Enschede, 7500 AE, The Netherlands
| | - Frieder Mugele
- Physics of Complex Fluids Group and MESA+ Institute, Faculty of Science and Technology, University of Twente, P.O. Box 217, Enschede, 7500 AE, The Netherlands
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12
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Jakub Z, Meier M, Kraushofer F, Balajka J, Pavelec J, Schmid M, Franchini C, Diebold U, Parkinson GS. Rapid oxygen exchange between hematite and water vapor. Nat Commun 2021; 12:6488. [PMID: 34759277 PMCID: PMC8580966 DOI: 10.1038/s41467-021-26601-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Accepted: 10/13/2021] [Indexed: 11/14/2022] Open
Abstract
Oxygen exchange at oxide/liquid and oxide/gas interfaces is important in technology and environmental studies, as it is closely linked to both catalytic activity and material degradation. The atomic-scale details are mostly unknown, however, and are often ascribed to poorly defined defects in the crystal lattice. Here we show that even thermodynamically stable, well-ordered surfaces can be surprisingly reactive. Specifically, we show that all the 3-fold coordinated lattice oxygen atoms on a defect-free single-crystalline "r-cut" ([Formula: see text]) surface of hematite (α-Fe2O3) are exchanged with oxygen from surrounding water vapor within minutes at temperatures below 70 °C, while the atomic-scale surface structure is unperturbed by the process. A similar behavior is observed after liquid-water exposure, but the experimental data clearly show most of the exchange happens during desorption of the final monolayer, not during immersion. Density functional theory computations show that the exchange can happen during on-surface diffusion, where the cost of the lattice oxygen extraction is compensated by the stability of an HO-HOH-OH complex. Such insights into lattice oxygen stability are highly relevant for many research fields ranging from catalysis and hydrogen production to geochemistry and paleoclimatology.
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Affiliation(s)
- Zdenek Jakub
- Institute of Applied Physics, TU Wien, Vienna, Austria
- Central European Institute of Technology (CEITEC), Brno University of Technology, Brno, Czech Republic
| | - Matthias Meier
- Institute of Applied Physics, TU Wien, Vienna, Austria
- University of Vienna, Faculty of Physics and Center for Computational Materials Science, Vienna, Austria
| | | | - Jan Balajka
- Institute of Applied Physics, TU Wien, Vienna, Austria
| | - Jiri Pavelec
- Institute of Applied Physics, TU Wien, Vienna, Austria
| | | | - Cesare Franchini
- University of Vienna, Faculty of Physics and Center for Computational Materials Science, Vienna, Austria
- Alma Mater Studiorum-Università di Bologna, Bologna, Italy
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13
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Baeumer C, Li J, Lu Q, Liang AYL, Jin L, Martins HP, Duchoň T, Glöß M, Gericke SM, Wohlgemuth MA, Giesen M, Penn EE, Dittmann R, Gunkel F, Waser R, Bajdich M, Nemšák S, Mefford JT, Chueh WC. Tuning electrochemically driven surface transformation in atomically flat LaNiO 3 thin films for enhanced water electrolysis. NATURE MATERIALS 2021; 20:674-682. [PMID: 33432142 DOI: 10.1038/s41563-020-00877-1] [Citation(s) in RCA: 43] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Accepted: 11/13/2020] [Indexed: 05/06/2023]
Abstract
Structure-activity relationships built on descriptors of bulk and bulk-terminated surfaces are the basis for the rational design of electrocatalysts. However, electrochemically driven surface transformations complicate the identification of such descriptors. Here we demonstrate how the as-prepared surface composition of (001)-terminated LaNiO3 epitaxial thin films dictates the surface transformation and the electrocatalytic activity for the oxygen evolution reaction. Specifically, the Ni termination (in the as-prepared state) is considerably more active than the La termination, with overpotential differences of up to 150 mV. A combined electrochemical, spectroscopic and density-functional theory investigation suggests that this activity trend originates from a thermodynamically stable, disordered NiO2 surface layer that forms during the operation of Ni-terminated surfaces, which is kinetically inaccessible when starting with a La termination. Our work thus demonstrates the tunability of surface transformation pathways by modifying a single atomic layer at the surface and that active surface phases only develop for select as-synthesized surface terminations.
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Affiliation(s)
- Christoph Baeumer
- Department of Materials Science and Engineering, Stanford University, Stanford, CA, USA.
- Stanford Institute for Materials and Energy Science, SLAC National Accelerator Laboratory, Menlo Park, CA, USA.
- Institute of Electronic Materials (IWE2) and JARA-FIT, RWTH Aachen University, Aachen, Germany.
- MESA+ Institute for Nanotechnology, Faculty of Science and Technology, University of Twente, Enschede, Netherlands.
| | - Jiang Li
- SUNCAT Center for Interface Science and Catalysis, SLAC National Laboratory, Menlo Park, CA, USA
| | - Qiyang Lu
- Department of Materials Science and Engineering, Stanford University, Stanford, CA, USA
- Stanford Institute for Materials and Energy Science, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- School of Engineering, Westlake University, Hangzhou, China
| | - Allen Yu-Lun Liang
- Stanford Institute for Materials and Energy Science, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
- Department of Chemistry, Stanford University, Stanford, CA, USA
| | - Lei Jin
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons (ER-C), Forschungszentrum Juelich GmbH, Juelich, Germany
| | | | - Tomáš Duchoň
- Peter Gruenberg Institute and JARA-FIT, Forschungszentrum Juelich GmbH, Juelich, Germany
| | - Maria Glöß
- Peter Gruenberg Institute and JARA-FIT, Forschungszentrum Juelich GmbH, Juelich, Germany
- Leibniz-Institute of Surface Engineering (IOM), Leipzig, Germany
| | - Sabrina M Gericke
- Chemical Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Combustion Physics, Lund University, Lund, Sweden
| | - Marcus A Wohlgemuth
- Peter Gruenberg Institute and JARA-FIT, Forschungszentrum Juelich GmbH, Juelich, Germany
| | - Margret Giesen
- Peter Gruenberg Institute and JARA-FIT, Forschungszentrum Juelich GmbH, Juelich, Germany
| | - Emily E Penn
- Department of Chemical Engineering, Stanford University, Stanford, CA, USA
| | - Regina Dittmann
- Peter Gruenberg Institute and JARA-FIT, Forschungszentrum Juelich GmbH, Juelich, Germany
| | - Felix Gunkel
- Peter Gruenberg Institute and JARA-FIT, Forschungszentrum Juelich GmbH, Juelich, Germany
| | - Rainer Waser
- Institute of Electronic Materials (IWE2) and JARA-FIT, RWTH Aachen University, Aachen, Germany
- Peter Gruenberg Institute and JARA-FIT, Forschungszentrum Juelich GmbH, Juelich, Germany
| | - Michal Bajdich
- SUNCAT Center for Interface Science and Catalysis, SLAC National Laboratory, Menlo Park, CA, USA.
| | - Slavomír Nemšák
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
- Peter Gruenberg Institute and JARA-FIT, Forschungszentrum Juelich GmbH, Juelich, Germany.
| | - J Tyler Mefford
- Department of Materials Science and Engineering, Stanford University, Stanford, CA, USA
- Stanford Institute for Materials and Energy Science, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - William C Chueh
- Department of Materials Science and Engineering, Stanford University, Stanford, CA, USA
- Stanford Institute for Materials and Energy Science, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
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14
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Hess F, Yildiz B. Precipitation of dopants on acceptor-doped LaMnO 3±δ revealed by defect chemistry from first principles. J Chem Phys 2021; 154:064702. [PMID: 33588549 DOI: 10.1063/5.0035691] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Perovskite oxides degrade at elevated temperatures while precipitating dopant-rich particles on the surface. A knowledge-based improvement of surface stability requires a fundamental and quantitative understanding of the dopant precipitation mechanism on these materials. We propose that dopant precipitation is a consequence of the variation of dopant solubility between calcination and operating conditions in solid oxide fuel cells (SOFCs) and electrolyzer cells (SOECs). To study dopant precipitation, we use 20% (D = Ca, Sr, Ba)-doped LaMnO3+δ (LDM20) as a model system. We employ a defect model taking input from density functional theory calculations. The defect model considers the equilibration of LDM20 with a reservoir consisting of dopant oxide (DO), peroxide (DO2), and O2 in the gas phase. The equilibrated non-stoichiometry of the A-site and B-site as a function of temperature, T, and oxygen partial pressure, p(O2), reveals three regimes for LDM20: A-site deficient (oxidizing conditions), A-site rich (atmospheric conditions), and near-stoichiometric (reducing conditions). Assuming an initial A/B non-stoichiometry, we compute the dopant precipitation boundaries in a p-T phase diagram. Our model predicts precipitation both under reducing (DO) and under highly oxidizing conditions (DO2). We found precipitation under anodic, SOEC conditions to be promoted by large dopant size, while under cathodic, SOFC conditions precipitation is promoted by initial A-site excess. The main driving forces for precipitation are oxygen uptake by the condensed phase under oxidizing conditions and oxygen release assisted by B-site vacancies under reducing conditions. Possible strategies for mitigating dopant precipitation under in electrolytic and fuel cell conditions are discussed.
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Affiliation(s)
- Franziska Hess
- Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
| | - Bilge Yildiz
- Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
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15
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Wells MP, Lovett AJ, Chalklen T, Baiutti F, Tarancón A, Wang X, Ding J, Wang H, Kar-Narayan S, Acosta M, MacManus-Driscoll JL. Route to High-Performance Micro-solid Oxide Fuel Cells on Metallic Substrates. ACS APPLIED MATERIALS & INTERFACES 2021; 13:4117-4125. [PMID: 33428400 PMCID: PMC7844816 DOI: 10.1021/acsami.0c15368] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Accepted: 12/24/2020] [Indexed: 06/12/2023]
Abstract
Micro-solid oxide fuel cells based on thin films have strong potential for use in portable power devices. However, devices based on silicon substrates typically involve thin-film metallic electrodes which are unstable at high temperatures. Devices based on bulk metal substrates overcome these limitations, though performance is hindered by the challenge of growing state-of-the-art epitaxial materials on metals. Here, we demonstrate for the first time the growth of epitaxial cathode materials on metal substrates (stainless steel) commercially supplied with epitaxial electrolyte layers (1.5 μm (Y2O3)0.15(ZrO2)0.85 (YSZ) + 50 nm CeO2). We create epitaxial mesoporous cathodes of (La0.60Sr0.40)0.95Co0.20Fe0.80O3 (LSCF) on the substrate by growing LSCF/MgO vertically aligned nanocomposite films by pulsed laser deposition, followed by selectively etching out the MgO. To enable valid comparison with the literature, the cathodes are also grown on single-crystal substrates, confirming state-of-the-art performance with an area specific resistance of 100 Ω cm2 at 500 °C and activation energy down to 0.97 eV. The work marks an important step toward the commercialization of high-performance micro-solid oxide fuel cells for portable power applications.
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Affiliation(s)
- Matthew P. Wells
- Department
of Materials Science and Metallurgy, University
of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, U.K.
| | - Adam J. Lovett
- Department
of Materials Science and Metallurgy, University
of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, U.K.
| | - Thomas Chalklen
- Department
of Materials Science and Metallurgy, University
of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, U.K.
| | - Federico Baiutti
- Department
of Advanced Materials for Energy, Catalonia
Institute for Energy Research (IREC), 1 Jardins de les Dones de Negre, Barcelona 08930, Spain
| | - Albert Tarancón
- Department
of Advanced Materials for Energy, Catalonia
Institute for Energy Research (IREC), 1 Jardins de les Dones de Negre, Barcelona 08930, Spain
- ICREA, 23 Passeig Lluís Companys, Barcelona 08010, Spain
| | - Xuejing Wang
- School
of Materials Engineering, Purdue University, 701 West Stadium Avenue, West Lafayette, Indiana 47907-2045, United States
| | - Jie Ding
- School
of Materials Engineering, Purdue University, 701 West Stadium Avenue, West Lafayette, Indiana 47907-2045, United States
| | - Haiyan Wang
- School
of Materials Engineering, Purdue University, 701 West Stadium Avenue, West Lafayette, Indiana 47907-2045, United States
| | - Sohini Kar-Narayan
- Department
of Materials Science and Metallurgy, University
of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, U.K.
| | - Matias Acosta
- Department
of Materials Science and Metallurgy, University
of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, U.K.
| | - Judith L. MacManus-Driscoll
- Department
of Materials Science and Metallurgy, University
of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, U.K.
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16
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Timmermann J, Kraushofer F, Resch N, Li P, Wang Y, Mao Z, Riva M, Lee Y, Staacke C, Schmid M, Scheurer C, Parkinson GS, Diebold U, Reuter K. IrO_{2} Surface Complexions Identified through Machine Learning and Surface Investigations. PHYSICAL REVIEW LETTERS 2020; 125:206101. [PMID: 33258623 DOI: 10.1103/physrevlett.125.206101] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2020] [Accepted: 09/22/2020] [Indexed: 06/12/2023]
Abstract
A Gaussian approximation potential was trained using density-functional theory data to enable a global geometry optimization of low-index rutile IrO_{2} facets through simulated annealing. Ab initio thermodynamics identifies (101) and (111) (1×1) terminations competitive with (110) in reducing environments. Experiments on single crystals find that (101) facets dominate and exhibit the theoretically predicted (1×1) periodicity and x-ray photoelectron spectroscopy core-level shifts. The obtained structures are analogous to the complexions discussed in the context of ceramic battery materials.
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Affiliation(s)
- Jakob Timmermann
- Chair for Theoretical Chemistry and Catalysis Research Center, Technical University of Munich, Lichtenbergstrasse 4, D-85747 Garching, Germany
| | - Florian Kraushofer
- Institute of Applied Physics, Technical University of Vienna, Wiedner Hauptstrasse 8-10/134, A-1040 Vienna, Austria
| | - Nikolaus Resch
- Institute of Applied Physics, Technical University of Vienna, Wiedner Hauptstrasse 8-10/134, A-1040 Vienna, Austria
| | - Peigang Li
- Department of Physics and Engineering Physics, Tulane University, New Orleans, Louisiana 70118, USA
| | - Yu Wang
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Zhiqiang Mao
- Department of Physics and Engineering Physics, Tulane University, New Orleans, Louisiana 70118, USA
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Michele Riva
- Institute of Applied Physics, Technical University of Vienna, Wiedner Hauptstrasse 8-10/134, A-1040 Vienna, Austria
| | - Yonghyuk Lee
- Chair for Theoretical Chemistry and Catalysis Research Center, Technical University of Munich, Lichtenbergstrasse 4, D-85747 Garching, Germany
| | - Carsten Staacke
- Chair for Theoretical Chemistry and Catalysis Research Center, Technical University of Munich, Lichtenbergstrasse 4, D-85747 Garching, Germany
| | - Michael Schmid
- Institute of Applied Physics, Technical University of Vienna, Wiedner Hauptstrasse 8-10/134, A-1040 Vienna, Austria
| | - Christoph Scheurer
- Chair for Theoretical Chemistry and Catalysis Research Center, Technical University of Munich, Lichtenbergstrasse 4, D-85747 Garching, Germany
| | - Gareth S Parkinson
- Institute of Applied Physics, Technical University of Vienna, Wiedner Hauptstrasse 8-10/134, A-1040 Vienna, Austria
| | - Ulrike Diebold
- Institute of Applied Physics, Technical University of Vienna, Wiedner Hauptstrasse 8-10/134, A-1040 Vienna, Austria
| | - Karsten Reuter
- Chair for Theoretical Chemistry and Catalysis Research Center, Technical University of Munich, Lichtenbergstrasse 4, D-85747 Garching, Germany
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
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17
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Dagdeviren OE, Mascaro A, Yuan S, Shirani J, Bevan KH, Grütter P. Ergodic and Nonergodic Dynamics of Oxygen Vacancy Migration at the Nanoscale in Inorganic Perovskites. NANO LETTERS 2020; 20:7530-7535. [PMID: 32969659 DOI: 10.1021/acs.nanolett.0c03002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Perovskites are widely utilized either as a primary component or as a substrate in which the dynamics of charged oxygen vacancy defects play an important role. Current knowledge regarding the dynamics of vacancy mobility in perovskites is solely based upon volume- and/or time-averaged measurements. This impedes our understanding of the basic physical principles governing defect migration in inorganic materials. Here, we measure the ergodic and nonergodic dynamics of vacancy migration at the relevant spatial and temporal scales using time-resolved atomic force microscopy techniques. Our findings demonstrate that the time constant associated with oxygen vacancy migration is a local property and can change drastically on short length and time scales, such that nonergodic states lead to a dramatic increase in the migration barrier. This correlated spatial and temporal variation in oxygen vacancy dynamics can extend hundreds of nanometers across the surface in inorganic perovskites.
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Affiliation(s)
- Omur E Dagdeviren
- Department of Mechanical Engineering, École de Technologie Supérieure, University of Quebec, Montreal, Quebec, Canada, H3C 1K3
- Department of Physics, McGill University, Montreal, Quebec, Canada, H3A 2T8
| | - Aaron Mascaro
- Department of Physics, McGill University, Montreal, Quebec, Canada, H3A 2T8
| | - Shuaishuai Yuan
- Materials Engineering, McGill University, Montreal, Quebec, Canada, H3A 0C5
| | - Javad Shirani
- Materials Engineering, McGill University, Montreal, Quebec, Canada, H3A 0C5
| | - Kirk H Bevan
- Materials Engineering, McGill University, Montreal, Quebec, Canada, H3A 0C5
| | - Peter Grütter
- Department of Physics, McGill University, Montreal, Quebec, Canada, H3A 2T8
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18
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Franceschi G, Schmid M, Diebold U, Riva M. Movable holder for a quartz crystal microbalance for exact growth rates in pulsed laser deposition. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2020; 91:065003. [PMID: 32611011 DOI: 10.1063/5.0007643] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2020] [Accepted: 05/29/2020] [Indexed: 06/11/2023]
Abstract
Controlling the amount of material deposited by pulsed laser deposition (PLD) down to fractions of one atomic layer is crucial for nanoscale technologies based on thin-film heterostructures. Albeit unsurpassed for measuring growth rates with high accuracy, the quartz crystal microbalance (QCM) suffers from some limitations when applied to PLD. The strong directionality of the PLD plasma plume and its pronounced dependence on deposition parameters (e.g., background pressure and fluence) require that the QCM is placed at the same position as the substrate during growth. However, QCM sensors are commonly fixed off to one side of the substrate. This also entails fast degradation of the crystal, as it is constantly exposed to the ablated material. The design for a movable QCM holder discussed in this work overcomes these issues. The holder is compatible with standard transfer arms, enabling easy insertion and transfer between a PLD chamber and other adjoining vacuum chambers. The QCM can be placed at the same position as the substrate during PLD growth. Its resonance frequency is measured in vacuum at any location where it can be in contact with an electrical feedthrough, before and after deposition. We tested the design for the deposition of hematite (Fe2O3), comparing the rates derived from the QCM and from reflection high-energy electron diffraction oscillations during homoepitaxial growth.
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Affiliation(s)
- Giada Franceschi
- Institute of Applied Physics, TU Wien, Wiedner Hauptstraße 8-10/E134, 1040 Wien, Austria
| | - Michael Schmid
- Institute of Applied Physics, TU Wien, Wiedner Hauptstraße 8-10/E134, 1040 Wien, Austria
| | - Ulrike Diebold
- Institute of Applied Physics, TU Wien, Wiedner Hauptstraße 8-10/E134, 1040 Wien, Austria
| | - Michele Riva
- Institute of Applied Physics, TU Wien, Wiedner Hauptstraße 8-10/E134, 1040 Wien, Austria
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19
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Franceschi G, Kraushofer F, Meier M, Parkinson GS, Schmid M, Diebold U, Riva M. A Model System for Photocatalysis: Ti-Doped α-Fe 2O 3(11̅02) Single-Crystalline Films. CHEMISTRY OF MATERIALS : A PUBLICATION OF THE AMERICAN CHEMICAL SOCIETY 2020; 32:3753-3764. [PMID: 32421058 PMCID: PMC7222102 DOI: 10.1021/acs.chemmater.9b04908] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Revised: 04/08/2020] [Indexed: 06/11/2023]
Abstract
Hematite (α-Fe2O3) is one of the most investigated anode materials for photoelectrochemical water splitting. Its efficiency improves by doping with Ti, but the underlying mechanisms are not understood. One hurdle is separating the influence of doping on conductivity, surface states, and morphology, which all affect performance. To address this complexity, one needs well-defined model systems. We build such a model system by growing single-crystalline, atomically flat Ti-doped α-Fe2O3(11̅02) films by pulsed laser deposition (PLD). We characterize their surfaces, combining in situ scanning tunneling microscopy (STM) with density functional theory (DFT), and reveal how dilute Ti impurities modify the atomic-scale structure of the surface as a function of the oxygen chemical potential and Ti content. Ti preferentially substitutes subsurface Fe and causes a local restructuring of the topmost surface layers. Based on the experimental quantification of Ti-induced surface modifications and the structural model we have established, we propose a strategy that can be used to separate the effects of Ti-induced modifications to the surface atomic and electronic structures and bulk conductivity on the reactivity of Ti-doped hematite.
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Affiliation(s)
- Giada Franceschi
- Institute
of Applied Physics, TU Wien, Wiedner Hauptstraβe 8-10/E134, 1040 Wien, Austria
| | - Florian Kraushofer
- Institute
of Applied Physics, TU Wien, Wiedner Hauptstraβe 8-10/E134, 1040 Wien, Austria
| | - Matthias Meier
- Institute
of Applied Physics, TU Wien, Wiedner Hauptstraβe 8-10/E134, 1040 Wien, Austria
- Faculty
of Physics and Center for Computational Materials Science, University of Vienna, Sensengasse 8, 1090 Wien, Austria
| | - Gareth S. Parkinson
- Institute
of Applied Physics, TU Wien, Wiedner Hauptstraβe 8-10/E134, 1040 Wien, Austria
| | - Michael Schmid
- Institute
of Applied Physics, TU Wien, Wiedner Hauptstraβe 8-10/E134, 1040 Wien, Austria
| | - Ulrike Diebold
- Institute
of Applied Physics, TU Wien, Wiedner Hauptstraβe 8-10/E134, 1040 Wien, Austria
| | - Michele Riva
- Institute
of Applied Physics, TU Wien, Wiedner Hauptstraβe 8-10/E134, 1040 Wien, Austria
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20
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Spray‐Flame‐Prepared LaCo
1–
x
Fe
x
O
3
Perovskite Nanoparticles as Active OER Catalysts: Influence of Fe Content and Low‐Temperature Heating. ChemElectroChem 2020. [DOI: 10.1002/celc.201902051] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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21
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Peculiar Properties of Electrochemically Oxidized SmBaCo2−xMnxO5+δ (x = 0; 0.5 and 1) A-Site Ordered Perovskites. CRYSTALS 2020. [DOI: 10.3390/cryst10030205] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Fully-stoichiometric SmBaCo2-xMnxO6 oxides (x = 0, 0.5, 1) were obtained through the electrochemical oxidation method performed in 1 M KOH solution from starting materials having close to equilibrium oxygen content. Cycling voltammetry scans allow us to recognize the voltage range (0.3–0.55 V vs. Hg/HgO electrode) for which electrochemical oxidation occurs with high efficiency. In a similarly performed galvanostatic experiment, the value of the stabilized voltage recorded during the oxidation increased with higher Mn content, which seems to relate to the electronic structure of the compounds. Results of the iodometric titration and thermogravimetric analysis prove that the proposed technique allows for an increase in the oxygen content in SmBaCo2-xMnxO5+δ materials to values close to 6 (δ ≈ 1). While the expected significant enhancement of the total conductivity was observed for the oxidized samples, surprisingly, their crystal structure only underwent slight modification. This can be interpreted as due to the unique nature of the oxygen intercalation process at room temperature.
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22
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Chen D, Guan Z, Zhang D, Trotochaud L, Crumlin E, Nemsak S, Bluhm H, Tuller HL, Chueh WC. Constructing a pathway for mixed ion and electron transfer reactions for O2 incorporation in Pr0.1Ce0.9O2−x. Nat Catal 2020. [DOI: 10.1038/s41929-019-0401-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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23
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Portugal GR, Arantes JT. Structural and electronic properties of NaTaO3 cubic nanowires. Phys Chem Chem Phys 2020; 22:7250-7258. [DOI: 10.1039/c9cp06769h] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Sodium tantalate 1-D nanostructures show novel properties due to their edge confinement region, which may be relevant for distinct applications.
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Affiliation(s)
- Guilherme Ribeiro Portugal
- Federal University of ABC (UFABC)
- Center for Engineering
- Modeling and Applied Social Science – CECS
- Santo André
- Brazil
| | - Jeverson Teodoro Arantes
- Federal University of ABC (UFABC)
- Center for Engineering
- Modeling and Applied Social Science – CECS
- Santo André
- Brazil
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