1
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He W, Shen Y, Wohlfeld K, Sears J, Li J, Pelliciari J, Walicki M, Johnston S, Baldini E, Bisogni V, Mitrano M, Dean MPM. Magnetically propagating Hund's exciton in van der Waals antiferromagnet NiPS 3. Nat Commun 2024; 15:3496. [PMID: 38664432 PMCID: PMC11045826 DOI: 10.1038/s41467-024-47852-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2023] [Accepted: 04/11/2024] [Indexed: 04/28/2024] Open
Abstract
Magnetic van der Waals (vdW) materials have opened new frontiers for realizing novel many-body phenomena. Recently NiPS3 has received intense interest since it hosts an excitonic quasiparticle whose properties appear to be intimately linked to the magnetic state of the lattice. Despite extensive studies, the electronic character, mobility, and magnetic interactions of the exciton remain unresolved. Here we address these issues by measuring NiPS3 with ultra-high energy resolution resonant inelastic x-ray scattering (RIXS). We find that Hund's exchange interactions are primarily responsible for the energy of formation of the exciton. Measuring the dispersion of the Hund's exciton reveals that it propagates in a way that is analogous to a double-magnon. We trace this unique behavior to fundamental similarities between the NiPS3 exciton hopping and spin exchange processes, underlining the unique magnetic characteristics of this novel quasiparticle.
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Affiliation(s)
- W He
- Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, NY, 11973, USA.
| | - Y Shen
- Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - K Wohlfeld
- Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, Warsaw, PL-02093, Poland
| | - J Sears
- Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - J Li
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - J Pelliciari
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - M Walicki
- Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, Warsaw, PL-02093, Poland
| | - S Johnston
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, TN, 37996, USA
- Institute of Advanced Materials and Manufacturing, The University of Tennessee, Knoxville, TN, 37996, USA
| | - E Baldini
- Department of Physics, The University of Texas at Austin, Austin, TX, 78712, USA
| | - V Bisogni
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - M Mitrano
- Department of Physics, Harvard University, Cambridge, MA, 02138, USA
| | - M P M Dean
- Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, NY, 11973, USA.
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2
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Wang L, Li Y, Xie SY, Liu F, Sun H, Huang C, Gao Y, Nakagawa T, Fu B, Dong B, Cao Z, Yu R, Kawaguchi SI, Kadobayashi H, Wang M, Jin C, Mao HK, Liu H. Structure Responsible for the Superconducting State in La 3Ni 2O 7 at High-Pressure and Low-Temperature Conditions. J Am Chem Soc 2024; 146:7506-7514. [PMID: 38457476 DOI: 10.1021/jacs.3c13094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/10/2024]
Abstract
Very recently, a new superconductor with Tc = 80 K has been reported in nickelate (La3Ni2O7) at around 15-40 GPa conditions (Nature, 621, 493, 2023), which is the second type of unconventional superconductor, besides cuprates, with Tc above liquid nitrogen temperature. However, the phase diagram plotted in this report was mostly based on the transport measurement under low-temperature and high-pressure conditions, and the assumed corresponding X-ray diffraction (XRD) results were carried out at room temperature. This encouraged us to carry out in situ high-pressure and low-temperature synchrotron XRD experiments to determine which phase is responsible for the high Tc state. In addition to the phase transition from the orthorhombic Amam structure to the orthorhombic Fmmm structure, a tetragonal phase with the space group of I4/mmm was discovered when the sample was compressed to around 19 GPa at 40 K where the superconductivity takes place in La3Ni2O7. The calculations based on this tetragonal structure reveal that the electronic states that approached the Fermi energy were mainly dominated by the eg orbitals (3dz2 and 3dx2-y2) of Ni atoms, which are located in the oxygen octahedral crystal field. The correlation between Tc and this structural evolution, especially Ni-O octahedra regularity and the in-plane Ni-O-Ni bonding angles, is analyzed. This work sheds new light to identify what is the most likely phase responsible for superconductivity in double-layered nickelate.
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Affiliation(s)
- Luhong Wang
- Shanghai Key Laboratory of Material Frontiers Research in Extreme Environments, Shanghai Advanced Research in Physical Sciences, Shanghai 201203, China
| | - Yan Li
- State Key Lab of Superhard Materials, College of Physics, Jilin University, Changchun 130012, China
| | - Sheng-Yi Xie
- School of Physics and Electronics, Hunan University, Changsha 410082, China
| | - Fuyang Liu
- Center for High Pressure Science & Technology Advanced Research, Beijing 100094, China
| | - Hualei Sun
- School of Sciences, Sun Yat-Sen University, Guangzhou, Guangdong 510275, China
| | - Chaoxin Huang
- Center for Neutron Science and Technology, Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices, School of Physics, Sun Yat-Sen University, Guangzhou, Guangdong 510275, China
| | - Yang Gao
- Center for High Pressure Science & Technology Advanced Research, Beijing 100094, China
| | - Takeshi Nakagawa
- Center for High Pressure Science & Technology Advanced Research, Beijing 100094, China
| | - Boyang Fu
- School of Materials and Energy, University of Electronic Science and Technology of China, Chengdu, Sichuan 611731, China
| | - Bo Dong
- Harbin Institute of Technology, Harbin 150001, China
| | - Zhenhui Cao
- State Key Lab of Superhard Materials, College of Physics, Jilin University, Changchun 130012, China
| | - Runze Yu
- Center for High Pressure Science & Technology Advanced Research, Beijing 100094, China
| | - Saori I Kawaguchi
- Japan Synchrotron Radiation Research Institute, SPring-8, Sayo-gun Hyogo 679-5198, Japan
| | - Hirokazu Kadobayashi
- Japan Synchrotron Radiation Research Institute, SPring-8, Sayo-gun Hyogo 679-5198, Japan
| | - Meng Wang
- Center for Neutron Science and Technology, Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices, School of Physics, Sun Yat-Sen University, Guangzhou, Guangdong 510275, China
| | - Changqing Jin
- Beijing National Lab for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Ho-Kwang Mao
- Shanghai Advanced Research in Physical Sciences, Shanghai 201203, China
- Center for High Pressure Science & Technology Advanced Research, Beijing 100094, China
| | - Haozhe Liu
- Center for High Pressure Science & Technology Advanced Research, Beijing 100094, China
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3
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Wang Y, Chen J, Liu K, Wang M, Song D, Wang K. Computational Screening of La 2NiO 4+δ Cathodes with Ni Site Doping for Solid Oxide Fuel Cells. Inorg Chem 2023; 62:7574-7583. [PMID: 37133438 DOI: 10.1021/acs.inorgchem.3c01044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Doping on the crystal structure is a common strategy to modify electronic conductivity, ion conductivity, and thermal stability. In this work, a series of transition metal elements (Fe, Co, Cu, Ru, Rh, Pd, Os, Ir, and Pt) doped at the Ni site of La2NiO4+δ compounds as cathode materials of solid oxide fuel cells (SOFCs) are explored based on first-principles calculations, through which the determinant factors for interstitial oxygen formations and migrations are discussed at an atomistic level. The interstitial oxygen formation and migration energies for doped La2NiO4 are largely reduced in contrast to the pristine La2NiO4+δ, which is explained by charge density distributions, charge density gradients, and Bader charge differences. In addition, based on a negative correlation between formation energy and migration barrier, the promising cathode materials for SOFCs were screened out between the doped systems. The Fe-doped structures of x = 0.25, Ru-doped structures of x = 0.25 and x = 0.375, Rh-doped structures of x = 0.50, and Pd-doped structures of x = 0.375 and x = 0.50 are screened out with interstitial oxygen formation energy less than -3 eV and migration barrier less than 1.1 eV. In addition, DOS analysis indicates that doping to La2NiO4+δ also facilitates the electron conductions. Our work provides a theoretical guideline for the optimization and design of La2NiO4+δ-based cathode materials by doping.
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Affiliation(s)
- Yongqing Wang
- School of Mechanical and Power Engineering, Zhengzhou University, Zhengzhou, Henan 450001, China
- Key Laboratory of Process Heat Transfer and Energy Saving of Henan Province, Zhengzhou University, Zhengzhou, Henan 450002, China
| | - Jiangshuai Chen
- School of Mechanical and Power Engineering, Zhengzhou University, Zhengzhou, Henan 450001, China
- Key Laboratory of Process Heat Transfer and Energy Saving of Henan Province, Zhengzhou University, Zhengzhou, Henan 450002, China
| | - Keli Liu
- School of Mechanical and Power Engineering, Zhengzhou University, Zhengzhou, Henan 450001, China
- Key Laboratory of Process Heat Transfer and Energy Saving of Henan Province, Zhengzhou University, Zhengzhou, Henan 450002, China
| | - Mingyuan Wang
- School of Mechanics and Safety Engineering, Zhengzhou University, Zhengzhou, Henan 450001, China
- Key Laboratory of Process Heat Transfer and Energy Saving of Henan Province, Zhengzhou University, Zhengzhou, Henan 450002, China
| | - Dongxing Song
- School of Mechanics and Safety Engineering, Zhengzhou University, Zhengzhou, Henan 450001, China
- Key Laboratory of Process Heat Transfer and Energy Saving of Henan Province, Zhengzhou University, Zhengzhou, Henan 450002, China
| | - Ke Wang
- School of Mechanics and Safety Engineering, Zhengzhou University, Zhengzhou, Henan 450001, China
- Key Laboratory of Process Heat Transfer and Energy Saving of Henan Province, Zhengzhou University, Zhengzhou, Henan 450002, China
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4
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Yatoo MA, Seymour ID, Skinner SJ. Neutron diffraction and DFT studies of oxygen defect and transport in higher-order Ruddlesden-Popper phase materials. RSC Adv 2023; 13:13786-13797. [PMID: 37152577 PMCID: PMC10160924 DOI: 10.1039/d3ra01772a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Accepted: 04/24/2023] [Indexed: 05/09/2023] Open
Abstract
A series of higher-order Ruddlesden-Popper phase materials - La3PrNi3O10-δ , La2Pr2Ni3O10-δ and LaPr3Ni3O10-δ - were synthesised and investigated by neutron powder diffraction to understand the oxygen defect structure and propose possible pathways for oxygen transport in these materials. Further complimentary DFT calculations of the materials were performed to support the experimental analysis. All of the phases were hypostoichiometric and it was observed that the majority of the oxygen vacancies were confined to the perovskite layers, with a preference for equatorial oxygen sites. A particular preference for vacancies in O(1) and O(5) sites at high temperatures was observed from neutron diffraction measurements which were further complimented by DFT calculations wherein the vacancy formation energy was found to be lowest at the O(1) site. Also, a preference for a curved oxygen transport pathway around the NiO6 octahedra was observed which agrees with the published literature for Ruddlesden-Popper phase materials. Lattice parameters for all three compositions showed a linear increase with increasing temperature, but the increase was greatest in the c parameter while the b parameter showed only a slight increase when compared to the a parameter. The thermal expansion coefficient was calculated for all compositions and was found to be in the range 13.0-13.4 × 10-6 °C-1, which is compatible with the commonly used electrolyte materials for solid oxide fuel cells.
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Affiliation(s)
- Mudasir A Yatoo
- Imperial College London, Department of Materials, Faculty of Engineering Exhibition Road London SW7 2AZ UK
- EPSRC Centre for Doctoral Training in Advanced Characterisation of Materials Exhibition Road London SW7 2AZ UK
| | - Ieuan D Seymour
- Imperial College London, Department of Materials, Faculty of Engineering Exhibition Road London SW7 2AZ UK
| | - Stephen J Skinner
- Imperial College London, Department of Materials, Faculty of Engineering Exhibition Road London SW7 2AZ UK
- EPSRC Centre for Doctoral Training in Advanced Characterisation of Materials Exhibition Road London SW7 2AZ UK
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5
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High-Temperature Behavior, Oxygen Transport Properties, and Electrochemical Performance of Cu-Substituted Nd1.6Ca0.4NiO4+δ Electrode Materials. APPLIED SCIENCES-BASEL 2022. [DOI: 10.3390/app12083747] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
In this study, Nd1.6Ca0.4Ni1−yCuyO4+δ-based electrode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs) are investigated. Materials of the series (y = 0–0.4) are obtained by pyrolysis of glycerol-nitrate compositions. The study of crystal structure and high-temperature stability in air and under low oxygen partial pressure atmospheres are performed using high-resolution neutron and in situ X-ray powder diffraction. All the samples under the study assume a structure with Bmab sp.gr. below 350 °C and with I4/mmm sp.gr. above 500 °C. A transition in the volume thermal expansion coefficient values from 7.8–9.3 to 9.1–12.0 × 10−6, K−1 is observed at approximately 400 °C in air and 500 °C in helium.The oxygen self-diffusion coefficient values, obtained using isotope exchange, monotonically decrease with the Cu content increasing, while concentration dependence of the charge carriers goes through the maximum at x = 0.2. The Nd1.6Ca0.4Ni0.8Cu0.2O4+δ electrode materialdemonstrates chemical compatibility and superior electrochemical performance in the symmetrical cells with Ce0.8Sm0.2O1.9, BaCe0.8Sm0.2O3−δ, BaCe0.8Gd0.19Cu0.1O3−δ and BaCe0.5Zr0.3Y0.1Yb0.1O3−δ solid electrolytes, potentially for application in IT-SOFCs.
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6
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Fang B, Qi Z, Liu F, Zhang C, Li C, Ni J, Lin J, Lin B, Jiang L. Activity Enhancement of Ceria-supported Co-Mo Bimetallic Catalysts by Tuning Reducibility and Metal Enrichment. J Catal 2022. [DOI: 10.1016/j.jcat.2022.01.015] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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7
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Li L, Zhou J, Hu Z, Choi S, Kim G, Wang JQ, Zhang L. First-Principles Insight into the Effects of Intrinsic Oxygen Defects on Proton Conduction in Ruddlesden-Popper Oxides. J Phys Chem Lett 2021; 12:11503-11510. [PMID: 34797083 DOI: 10.1021/acs.jpclett.1c02749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Understanding proton transport in Ruddlesden-Popper (RP) oxides, as attractive electrode materials for protonic ceramic fuel cells, is challenging because of the complexity of intrinsic oxygen defects in first-series RP oxides (A2BO4). We investigated the processes of intrinsic oxygen defects in proton transportation, such as formation of defects, incorporation of dissociative water into the defective lattice, transfer of a proton along the oxygen sites, and electronic properties of the transition state (TS) in A2BO4. The coexistence of oxygen vacancies (VO) and interstitial oxygen (Oi), VO+Oi defect pair, presents advantageous hydration energies and lattice distortions efficiently accelerating proton transport in the lattice. Moreover, the inherent driving force for proton transport is related to the O 2p band level by O-H···O bond interactions in the TS. Our findings elucidate the fundamental mechanism of proton conduction affected by intrinsic oxygen defects, which will motivate the community to focus more on defect engineering to enhance performance.
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Affiliation(s)
- Lili Li
- Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
| | - Jing Zhou
- Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
| | - Zhiwei Hu
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, Dresden 01187, Germany
| | - Sihyuk Choi
- Department of Mechanical Engineering (Department of Aeronautics, Mechanical and Electronic Convergence Engineering), Kumoh National Institute of Technology, Gyeongbuk 39177, Republic of Korea
| | - Guntae Kim
- School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
| | - Jian-Qiang Wang
- Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
- University of Chinese Academy of Sciences, Beijing 100049, China
- Dalian National Laboratory for Clean Energy, Dalian 116023, P. R. China
| | - Linjuan Zhang
- Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
- University of Chinese Academy of Sciences, Beijing 100049, China
- Dalian National Laboratory for Clean Energy, Dalian 116023, P. R. China
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8
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Li Z, Li M, Zhu Z. Perovskite Cathode Materials for Low-Temperature Solid Oxide Fuel Cells: Fundamentals to Optimization. ELECTROCHEM ENERGY R 2021. [DOI: 10.1007/s41918-021-00098-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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9
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Abstract
We review oxygen K-edge X-ray absorption spectra of both molecules and solids. We start with an overview of the main experimental aspects of oxygen K-edge X-ray absorption measurements including X-ray sources, monochromators, and detection schemes. Many recent oxygen K-edge studies combine X-ray absorption with time and spatially resolved measurements and/or operando conditions. The main theoretical and conceptual approximations for the simulation of oxygen K-edges are discussed in the Theory section. We subsequently discuss oxygen atoms and ions, binary molecules, water, and larger molecules containing oxygen, including biomolecular systems. The largest part of the review deals with the experimental results for solid oxides, starting from s- and p-electron oxides. Examples of theoretical simulations for these oxides are introduced in order to show how accurate a DFT description can be in the case of s and p electron overlap. We discuss the general analysis of the 3d transition metal oxides including discussions of the crystal field effect and the effects and trends in oxidation state and covalency. In addition to the general concepts, we give a systematic overview of the oxygen K-edges element by element, for the s-, p-, d-, and f-electron systems.
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Affiliation(s)
- Federica Frati
- Inorganic
chemistry and catalysis, Debye Institute for Nanomaterials Science, Utrecht University, 3584CG Utrecht, The Netherlands
| | | | - Frank M. F. de Groot
- Inorganic
chemistry and catalysis, Debye Institute for Nanomaterials Science, Utrecht University, 3584CG Utrecht, The Netherlands
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10
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Constructing a direct Z-scheme La2NiO4/g-C3N4 hybrid photocatalyst with boosted visible light photocatalytic activity. Sep Purif Technol 2018. [DOI: 10.1016/j.seppur.2018.02.004] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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11
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Nakamura T, Oike R, Kimura Y, Tamenori Y, Kawada T, Amezawa K. Operando Soft X-ray Absorption Spectroscopic Study on a Solid Oxide Fuel Cell Cathode during Electrochemical Oxygen Reduction. CHEMSUSCHEM 2017; 10:2008-2014. [PMID: 28301085 DOI: 10.1002/cssc.201700237] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Revised: 03/16/2017] [Indexed: 06/06/2023]
Abstract
An operando soft X-ray absorption spectroscopic technique, which enabled the analysis of the electronic structures of the electrode materials at elevated temperature in a controlled atmosphere and electrochemical polarization, was established and its availability was demonstrated by investigating the electronic structural changes of an La2 NiO4+δ dense-film electrode during an electrochemical oxygen reduction reaction. Clear O K-edge and Ni L-edge X-ray absorption spectra could be obtained below 773 K under an atmospheric pressure of 100 ppm O2 /He, 0.1 % O2 /He, and 1 % O2 /He gas mixtures. Considerable spectral changes were observed in the O K-edge X-ray absorption spectra upon changing the PO2 and application of electrical potential, whereas only small spectral changes were observed in Ni L-edge X-ray absorption spectra. A pre-edge peak of the O K-edge X-ray absorption spectra, which reflects the unoccupied partial density of states of Ni 3d-O 2p hybridization, increased or decreased with cathodic or anodic polarization, respectively. The electronic structural changes of the outermost orbital of the electrode material due to electrochemical polarization were successfully confirmed by the operando X-ray absorption spectroscopic technique developed in this study.
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Affiliation(s)
- Takashi Nakamura
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan
| | - Ryo Oike
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan
| | - Yuta Kimura
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan
| | - Yusuke Tamenori
- Japan Synchrotron Radiation Institute, 1-1-1, Kouto, Sayo-cho, Sayo-gun, Hyogo, 679-5198, Japan
| | - Tatsuya Kawada
- Graduate School of Environmental Studies, Tohoku University, 6-6-1 Aramaki-Aoba, Aoba-ku, Sendai, 980-8579, Japan
| | - Koji Amezawa
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan
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12
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NAKAMURA T. Nonstoichiometry and the Origin of Electrochemical Properties of Functional Oxides for Energy Conversion and Storage Technologies. ELECTROCHEMISTRY 2017. [DOI: 10.5796/electrochemistry.85.552] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- Takashi NAKAMURA
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University
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13
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Xu P, Ayino Y, Cheng C, Pribiag VS, Comes RB, Sushko PV, Chambers SA, Jalan B. Predictive Control over Charge Density in the Two-Dimensional Electron Gas at the Polar-Nonpolar NdTiO_{3}/SrTiO_{3} Interface. PHYSICAL REVIEW LETTERS 2016; 117:106803. [PMID: 27636487 DOI: 10.1103/physrevlett.117.106803] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Indexed: 06/06/2023]
Abstract
Through systematic control of the Nd concentration, we show that the carrier density of the two-dimensional electron gas (2DEG) in SrTiO_{3}/NdTiO_{3}/SrTiO_{3}(001) can be modulated over a wide range. We also demonstrate that the NdTiO_{3} in heterojunctions without a SrTiO_{3} cap is degraded by oxygen absorption from air, resulting in the immobilization of donor electrons that could otherwise contribute to the 2DEG. This system is, thus, an ideal model to understand and control the insulator-to-metal transition in a 2DEG based on both environmental conditions and film-growth processing parameters.
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Affiliation(s)
- Peng Xu
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Yilikal Ayino
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Christopher Cheng
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Vlad S Pribiag
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Ryan B Comes
- Physical & Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, USA
| | - Peter V Sushko
- Physical & Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, USA
| | - Scott A Chambers
- Physical & Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, USA
| | - Bharat Jalan
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
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14
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Xie W, Lee YL, Shao-Horn Y, Morgan D. Oxygen Point Defect Chemistry in Ruddlesden-Popper Oxides (La1-xSrx)2MO4±δ (M = Co, Ni, Cu). J Phys Chem Lett 2016; 7:1939-44. [PMID: 27157124 DOI: 10.1021/acs.jpclett.6b00739] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Stability of oxygen point defects in Ruddlesden-Popper oxides (La1-xSrx)2MO4±δ (M = Co, Ni, Cu) is studied with density functional theory calculations to determine their stable sites, charge states, and energetics as functions of Sr content (x), transition metal (M), and defect concentration (δ). We demonstrate that the dominant O point defects can change between oxide interstitials, peroxide interstitials, and vacancies. In general, increasing x and atomic number of M stabilizes peroxide over oxide interstitials as well as vacancies over both peroxide and oxide interstitials; increasing δ destabilizes both oxide interstitials and vacancies but barely affects peroxide interstitials. We also demonstrate that the O 2p-band center is a powerful descriptor for these materials and correlates linearly with the formation energy of all defects. The trends of formation energy versus x, M, and δ and the correlation with O 2p-band center are explained in terms of oxidation chemistry and electronic structure.
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Affiliation(s)
- Wei Xie
- Department of Materials Science and Engineering, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
| | - Yueh-Lin Lee
- Department of Materials Science and Engineering, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
- Electrochemical Energy Laboratory, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Yang Shao-Horn
- Electrochemical Energy Laboratory, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Dane Morgan
- Department of Materials Science and Engineering, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
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15
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Li W, Guan B, Zhang X, Yan J, Zhou Y, Liu X. New mechanistic insight into the oxygen reduction reaction on Ruddlesden-Popper cathodes for intermediate-temperature solid oxide fuel cells. Phys Chem Chem Phys 2016; 18:8502-11. [PMID: 26939545 DOI: 10.1039/c6cp00056h] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ruddlesden-Popper (R-P) phase materials have been investigated widely as cathode candidates for IT-SOFCs. However, widespread application of R-P phase cathodes demands further improvement in electrode activity whose progress is hindered by the limited information in the oxygen reduction reaction (ORR). The ORR mechanism for the R-P phase is therefore investigated in this paper using (LaSr)2NiO(4±δ) as an example. Accurate characterization of the surface oxygen exchange process is realized by developing thin and dense polycrystalline LSNO layers via a versatile spray-modified pressing method we invented before to avoid perceptible bulk diffusion contribution, surface enrichment and geometry complication. The governing factors of the ORR are identified as oxygen adsorption and incorporation based on the findings in reaction orders from electrochemical impedance spectroscopy (EIS), stoichiometry-related chemical capacitance and intrinsic anisotropic properties. The incorporation rate is proven to drastically depend on the amount of interstitial oxygen (O(i)"). Since the unfilled interstitial sites(V(i)(×)) in the R-P phase serve to accommodate the adsorbed oxygen during incorporation, like vacancies in the perovskite structure (V(O)(••)), more O(i)" would seem to suppress the kinetics of this process. In regards to this, for the first time, a physical model is proposed to reconcile the discrepancy between the experimental results and intuitive reasoning. Based on supporting evidence, this model illustrates a possibility of how O(i)" works to regulate the exchange rate, and how the contradiction between V(O)(••) and O(i)" is harmonized so that the latter in the R-P structure also positively promotes the incorporation rate in the ORR.
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Affiliation(s)
- Wenyuan Li
- Mechanical & Aerospace Engineering Department, Benjamin M. Statler College of Engineering & Mineral Resources, West Virginia University, Morgantown, WV 26506-6106, USA.
| | - Bo Guan
- Mechanical & Aerospace Engineering Department, Benjamin M. Statler College of Engineering & Mineral Resources, West Virginia University, Morgantown, WV 26506-6106, USA.
| | - Xinxin Zhang
- Mechanical & Aerospace Engineering Department, Benjamin M. Statler College of Engineering & Mineral Resources, West Virginia University, Morgantown, WV 26506-6106, USA.
| | - Jianhua Yan
- Mechanical & Aerospace Engineering Department, Benjamin M. Statler College of Engineering & Mineral Resources, West Virginia University, Morgantown, WV 26506-6106, USA.
| | - Yue Zhou
- Mechanical & Aerospace Engineering Department, Benjamin M. Statler College of Engineering & Mineral Resources, West Virginia University, Morgantown, WV 26506-6106, USA.
| | - Xingbo Liu
- Mechanical & Aerospace Engineering Department, Benjamin M. Statler College of Engineering & Mineral Resources, West Virginia University, Morgantown, WV 26506-6106, USA.
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OIKE R, OKAMOTO Y, TOKUSHIMA T, NAKAMURA T, AMEZAWA K. In-situ Simultaneous Soft X-ray Absorption and Emission Spectroscopy under Controlled Atmosphere and Temperature. ELECTROCHEMISTRY 2016. [DOI: 10.5796/electrochemistry.84.793] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- Ryo OIKE
- Graduate School of Engineering, Tohoku University
- RIKEN SPring-8 Center
| | - Yusuke OKAMOTO
- RIKEN SPring-8 Center
- Graduate School of Environmental Studies, Tohoku University
| | | | - Takashi NAKAMURA
- RIKEN SPring-8 Center
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University
| | - Koji AMEZAWA
- RIKEN SPring-8 Center
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University
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