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Dong M, Zhang K, Wan X, Wang S, Fan S, Ye Z, Wang Y, Yan Y, Peng X. Stable Two-dimensional Nanoconfined Ionic Liquids with Highly Efficient Ionic Conductivity. Small 2022; 18:e2108026. [PMID: 35388646 DOI: 10.1002/smll.202108026] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2021] [Revised: 01/24/2022] [Indexed: 06/14/2023]
Abstract
Amid the burgeoning environmental concerns, electrochemical energy storage is of great demand, inspiring the rapid development of electrolytes. Quasi-liquid solid electrolytes (QLSEs) demonstrate exciting properties that combine high ionic conductivity and safety. Herein, a QLSE system is constructed by confining ionic liquids (ILs) into 2D materials-based membranes, which creates a subtle platform for the investigation of the nanoconfined ion transport process. The highest ionic conductivity increment of 506% can be observed when ILs are under nanoconfinement. Correlation of experimental results and simulation evidently prove the diffusion behaviors of ILs are remarkably accelerated when confined in nanochannels, ascribing from the promoted dissociation of ILs. Concurrently, nanoconfined ILs demonstrate a highly ordered distribution, lower interplay, and higher free volume compared against bulk systems. This work reveals and analyzes the phenomenon of ionic conductivity elevation in nanoconfined ILs, and offers inspiring opportunities to fabricate the highly stable and efficient QLSEs based on layered nanomaterials for energy storage applications.
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Affiliation(s)
- Mengyang Dong
- State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, 310027, China
| | - Kuiyuan Zhang
- School of Materials Science and Engineering, China University of Petroleum (East China), Qingdao, 266580, China
| | - Xinyi Wan
- State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, 310027, China
| | - Shilin Wang
- State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, 310027, China
| | - Shuaikang Fan
- State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, 310027, China
| | - ZhiZhen Ye
- State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, 310027, China
- Wenzhou Key Laboratory of Novel Optoelectronic and Nanomaterials, Institute of Wenzhou, Zhejiang University, Wenzhou, 325006, China
| | - Yuqi Wang
- State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, 310027, China
- Wenzhou Key Laboratory of Novel Optoelectronic and Nanomaterials, Institute of Wenzhou, Zhejiang University, Wenzhou, 325006, China
| | - Youguo Yan
- School of Materials Science and Engineering, China University of Petroleum (East China), Qingdao, 266580, China
| | - Xinsheng Peng
- State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, 310027, China
- Wenzhou Key Laboratory of Novel Optoelectronic and Nanomaterials, Institute of Wenzhou, Zhejiang University, Wenzhou, 325006, China
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Kim H, Lu K, Liu Y, Kum HS, Kim KS, Qiao K, Bae SH, Lee S, Ji YJ, Kim KH, Paik H, Xie S, Shin H, Choi C, Lee JH, Dong C, Robinson JA, Lee JH, Ahn JH, Yeom GY, Schlom DG, Kim J. Impact of 2D-3D Heterointerface on Remote Epitaxial Interaction through Graphene. ACS Nano 2021; 15:10587-10596. [PMID: 34081854 DOI: 10.1021/acsnano.1c03296] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Remote epitaxy has drawn attention as it offers epitaxy of functional materials that can be released from the substrates with atomic precision, thus enabling production and heterointegration of flexible, transferrable, and stackable freestanding single-crystalline membranes. In addition, the remote interaction of atoms and adatoms through two-dimensional (2D) materials in remote epitaxy allows investigation and utilization of electrical/chemical/physical coupling of bulk (3D) materials via 2D materials (3D-2D-3D coupling). Here, we unveil the respective roles and impacts of the substrate material, graphene, substrate-graphene interface, and epitaxial material for electrostatic coupling of these materials, which governs cohesive ordering and can lead to single-crystal epitaxy in the overlying film. We show that simply coating a graphene layer on wafers does not guarantee successful implementation of remote epitaxy, since atomically precise control of the graphene-coated interface is required, and provides key considerations for maximizing the remote electrostatic interaction between the substrate and adatoms. This was enabled by exploring various material systems and processing conditions, and we demonstrate that the rules of remote epitaxy vary significantly depending on the ionicity of material systems as well as the graphene-substrate interface and the epitaxy environment. The general rule of thumb discovered here enables expanding 3D material libraries that can be stacked in freestanding form.
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Affiliation(s)
- Hyunseok Kim
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Kuangye Lu
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Yunpeng Liu
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Hyun S Kum
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Ki Seok Kim
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Kuan Qiao
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Sang-Hoon Bae
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Sangho Lee
- Department of Mechanical 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
| | - You Jin Ji
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Ki Hyun Kim
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Hanjong Paik
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14850, United States
| | - Saien Xie
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14850, United States
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14850, United States
| | - Heechang Shin
- School of Electrical and Electronic Engineering, Yonsei University, Seoul 03722, Republic of Korea
| | - Chanyeol Choi
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - June Hyuk Lee
- Neutron Science Division, Korea Atomic Energy Research Institute, Daejeon 34057, Republic of Korea
| | - Chengye Dong
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- 2D Crystal Consortium, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Joshua A Robinson
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- 2D Crystal Consortium, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Jae-Hyun Lee
- Department of Energy Systems Research and Department of Materials Science and Engineering, Ajou University, Suwon 16499, Republic of Korea
| | - Jong-Hyun Ahn
- School of Electrical and Electronic Engineering, Yonsei University, Seoul 03722, Republic of Korea
| | - Geun Young Yeom
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
- SKKU Advanced Institute of Nano Technology (SAINT), Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Darrell G Schlom
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14850, United States
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14850, United States
- Leibniz-Institut für Kristallzüchtung, Berlin 12489, Germany
| | - Jeehwan Kim
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
- Microsystems Technology Laboratories, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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Cha S, Lee M, Kim D. Concentration Dependence of Ion Pairing in Imidazolium-Based Ionic Liquid Solutions. Chemphyschem 2019; 20:482-488. [PMID: 30565367 DOI: 10.1002/cphc.201800926] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 08/15/2018] [Indexed: 11/10/2022]
Abstract
Infrared vibrational spectroscopy was used to probe concentration-dependent ion pair dissociation of imidazolium-based ionic liquids with three different halide anions (I- , Br- , and Cl- ) in deuterated chloroform. Dissociation of the ion pairs at low concentrations of ionic liquids was found to be the easiest for ionic liquid with Cl- anion, the most electronegative anion among the three investigated. This anomalous trend of ion pair dissociation was explained in terms of varying interaction strength between the solvent (CDCl3 ) and the anions investigated.
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Affiliation(s)
- Seoncheol Cha
- Department of Physics, Sogang University, Seoul, Korea
| | - Minho Lee
- Department of Physics, Sogang University, Seoul, Korea
| | - Doseok Kim
- Department of Physics, Sogang University, Seoul, Korea
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Philippi F, Rauber D, Zapp J, Präsang C, Scheschkewitz D, Hempelmann R. Multiple Ether-Functionalized Phosphonium Ionic Liquids as Highly Fluid Electrolytes. Chemphyschem 2019; 20:443-455. [PMID: 30480374 DOI: 10.1002/cphc.201800939] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Revised: 11/22/2018] [Indexed: 11/11/2022]
Abstract
Ionic liquids (ILs) are promising electrolytes, although their often high viscosity remains a serious drawback. The latter can be addressed by the introduction of multiple ether functionalization. Based on the highly atom efficient synthesis of tris(2-ethoxyethyl) phosphine, several new phosphonium ionic liquids were prepared, which allows studying the influence of the ether side chains. Their most important physicochemical properties have been determined and will be interpreted using established approaches like ionicity, hole theory, and the Walden plot. There is striking evidence that the properties of phosphonium ionic liquids with the methanesulfonate anion are dominated by aggregation, whereas the two triple ether functionalized ILs with the highest fluidity show almost ideal behavior with other factors being dominant. It is furthermore found that the deviation from ideality is not significantly changed upon introduction of the ether side chains, although a very beneficial impact on the fluidity of ILs is observed. Multiple ether functionalization therefore proves as a powerful tool to overcome the disadvantages of phosphonium ionic liquids with large cations.
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Affiliation(s)
- Frederik Philippi
- Physical Chemistry, Saarland University, Campus B 2 2, 66123, Saarbrücken, Germany
| | - Daniel Rauber
- Physical Chemistry, Saarland University, Campus B 2 2, 66123, Saarbrücken, Germany.,Transfercentre Sustainable Electrochemistry, Saarland University and KIST Europe, Am Markt, Zeile 3, 66125, Saarbrücken, Germany
| | - Josef Zapp
- Pharmaceutical Biology, Saarland University, Campus B 2 3, 66123, Saarbrücken, Germany
| | - Carsten Präsang
- Krupp-Chair of General and Inorganic Chemistry, Saarland University, 66123, Saarbrücken, Germany
| | - David Scheschkewitz
- Krupp-Chair of General and Inorganic Chemistry, Saarland University, 66123, Saarbrücken, Germany
| | - Rolf Hempelmann
- Physical Chemistry, Saarland University, Campus B 2 2, 66123, Saarbrücken, Germany.,Transfercentre Sustainable Electrochemistry, Saarland University and KIST Europe, Am Markt, Zeile 3, 66125, Saarbrücken, Germany
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Fugel M, Hesse MF, Pal R, Beckmann J, Jayatilaka D, Turner MJ, Karton A, Bultinck P, Chandler GS, Grabowsky S. Covalency and Ionicity Do Not Oppose Each Other-Relationship Between Si-O Bond Character and Basicity of Siloxanes. Chemistry 2018; 24:15275-15286. [PMID: 29999553 DOI: 10.1002/chem.201802197] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Revised: 07/11/2018] [Indexed: 11/07/2022]
Abstract
Covalency and ionicity are orthogonal rather than antipodal concepts. We demonstrate for the case of siloxane systems [R3 Si-(O-SiR2 )n -O-SiR3 ] that both covalency and ionicity of the Si-O bonds impact on the basicity of the Si-O-Si linkage. The relationship between the siloxane basicity and the Si-O bond character has been under debate since previous studies have presented conflicting explanations. It has been shown with natural bond orbital methods that increased hyperconjugative interactions of LP(O)→σ*(Si-R) type, that is, increased orbital overlap and hence covalency, are responsible for the low siloxane basicity at large Si-O-Si angles. On the other hand, increased ionicity towards larger Si-O-Si angles has been revealed with real-space bonding indicators. To resolve this ostensible contradiction, we perform a complementary bonding analysis, which combines orbital-space, real-space, and bond-index considerations. We analyze the isolated disiloxane molecule H3 SiOSiH3 with varying Si-O-Si angles, and n-membered cyclic siloxane systems Si2 H4 O(CH2 )n-3 . All methods from quite different realms show that both covalent and ionic interactions increase simultaneously towards larger Si-O-Si angles. In addition, we present highly accurate absolute hydrogen-bond interaction energies of the investigated siloxane molecules with water and silanol as donors. It is found that intermolecular hydrogen bonding is significant at small Si-O-Si angles and weakens as the Si-O-Si angle increases until no stable hydrogen-bond complexes are obtained beyond φSiOSi =168°, angles typically displayed by minerals or polymers. The maximum hydrogen-bond interaction energy, which is obtained at an angle of 105°, is 11.05 kJ mol-1 for the siloxane-water complex and 18.40 kJ mol-1 for the siloxane-silanol complex.
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Affiliation(s)
- Malte Fugel
- University of Bremen, Department 2-Chemistry/Biology, Institute of Inorganic Chemistry and Crystallography, Leobener Str. 3 and 7, 28359, Bremen, Germany
| | - Maxie F Hesse
- University of Bremen, Department 2-Chemistry/Biology, Institute of Inorganic Chemistry and Crystallography, Leobener Str. 3 and 7, 28359, Bremen, Germany
| | - Rumpa Pal
- University of Bremen, Department 2-Chemistry/Biology, Institute of Inorganic Chemistry and Crystallography, Leobener Str. 3 and 7, 28359, Bremen, Germany
| | - Jens Beckmann
- University of Bremen, Department 2-Chemistry/Biology, Institute of Inorganic Chemistry and Crystallography, Leobener Str. 3 and 7, 28359, Bremen, Germany
| | - Dylan Jayatilaka
- University of Western Australia, School of Molecular Sciences, 35 Stirling Highway, Perth, WA, 6009, Australia
| | - Michael J Turner
- University of Western Australia, School of Molecular Sciences, 35 Stirling Highway, Perth, WA, 6009, Australia
| | - Amir Karton
- University of Western Australia, School of Molecular Sciences, 35 Stirling Highway, Perth, WA, 6009, Australia
| | - Patrick Bultinck
- Ghent University, Department of Chemistry, Krijgslaan 281 (S3), 9000, Gent, Belgium
| | - Graham S Chandler
- University of Western Australia, School of Molecular Sciences, 35 Stirling Highway, Perth, WA, 6009, Australia
| | - Simon Grabowsky
- University of Bremen, Department 2-Chemistry/Biology, Institute of Inorganic Chemistry and Crystallography, Leobener Str. 3 and 7, 28359, Bremen, Germany
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Pulst M, Golitsyn Y, Reichert D, Kressler J. Ion Transport Properties and Ionicity of 1,3-Dimethyl-1,2,3-Triazolium Salts with Fluorinated Anions. Materials (Basel) 2018; 11:E1723. [PMID: 30223444 PMCID: PMC6164264 DOI: 10.3390/ma11091723] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/23/2018] [Revised: 09/07/2018] [Accepted: 09/11/2018] [Indexed: 11/16/2022]
Abstract
1,2,3-Triazolium salts are an important class of materials with a plethora of sophisticated applications. A series of three novel 1,3-dimethyl-1,2,3-triazolium salts with fluorine, containing anions of various size, is synthesized by methylation of 1,2,3-triazole. Their ion conductivity is measured by impedance spectroscopy, and the corresponding ionicities are determined by diffusion coefficients obtained from ¹H and 19F pulsed field gradient nuclear magnetic resonance (PFG NMR) spectroscopy data, revealing that the anion strongly influences their ion conductive properties. Since the molar ion conductivities and ionicities of the 1,3-dimethyl-1,2,3-triazolium salts are enhanced in comparison to other 1,2,3-triazolium salts with longer alkyl substituents, they are promising candidates for applications as electrolytes in electrochemical devices.
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Affiliation(s)
- Martin Pulst
- Faculty of Natural Sciences II, Martin Luther University Halle-Wittenberg, D-06099 Halle (Saale), Germany.
| | - Yury Golitsyn
- Faculty of Natural Sciences II, Martin Luther University Halle-Wittenberg, D-06099 Halle (Saale), Germany.
| | - Detlef Reichert
- Faculty of Natural Sciences II, Martin Luther University Halle-Wittenberg, D-06099 Halle (Saale), Germany.
| | - Jörg Kressler
- Faculty of Natural Sciences II, Martin Luther University Halle-Wittenberg, D-06099 Halle (Saale), Germany.
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Alhameedi K, Karton A, Jayatilaka D, Thomas SP. Bond orders for intermolecular interactions in crystals: charge transfer, ionicity and the effect on intramolecular bonds. IUCrJ 2018; 5:635-646. [PMID: 30224966 PMCID: PMC6126646 DOI: 10.1107/s2052252518010758] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2018] [Accepted: 07/24/2018] [Indexed: 05/30/2023]
Abstract
The question of whether intermolecular interactions in crystals originate from localized atom⋯atom interactions or as a result of holistic molecule⋯molecule close packing is a matter of continuing debate. In this context, the newly introduced Roby-Gould bond indices are reported for intermolecular 'σ-hole' interactions, such as halogen bonding and chalcogen bonding, and compared with those for hydrogen bonds. A series of 97 crystal systems exhibiting these interaction motifs obtained from the Cambridge Structural Database (CSD) has been analysed. In contrast with conventional bond-order estimations, the new method separately estimates the ionic and covalent bond indices for atom⋯atom and molecule⋯molecule bond orders, which shed light on the nature of these interactions. A consistent trend in charge transfer from halogen/chalcogen bond-acceptor to bond-donor groups has been found in these intermolecular interaction regions via Hirshfeld atomic partitioning of the electron populations. These results, along with the 'conservation of bond orders' tested in the interaction regions, establish the significant role of localized atom⋯atom interactions in the formation of these intermolecular binding motifs.
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Affiliation(s)
- Khidhir Alhameedi
- School of Molecular Sciences, University of Western Australia, 35 Stirling Highway, Perth 6009, Australia
- College of Education for Pure Science, University of Karbala, Karbala, Iraq
| | - Amir Karton
- School of Molecular Sciences, University of Western Australia, 35 Stirling Highway, Perth 6009, Australia
| | - Dylan Jayatilaka
- School of Molecular Sciences, University of Western Australia, 35 Stirling Highway, Perth 6009, Australia
| | - Sajesh P. Thomas
- School of Molecular Sciences, University of Western Australia, 35 Stirling Highway, Perth 6009, Australia
- Centre for Materials Crystallography, Department of Chemistry and iNano, Aarhus University, Langelandsgade 140, Aarhus 8000, Denmark
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Angell M, Pan CJ, Rong Y, Yuan C, Lin MC, Hwang BJ, Dai H. High Coulombic efficiency aluminum-ion battery using an AlCl3-urea ionic liquid analog electrolyte. Proc Natl Acad Sci U S A 2017; 114:834-9. [PMID: 28096353 DOI: 10.1073/pnas.1619795114] [Citation(s) in RCA: 140] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In recent years, impressive advances in harvesting renewable energy have led to a pressing demand for the complimentary energy storage technology. Here, a high Coulombic efficiency (∼99.7%) Al battery is developed using earth-abundant aluminum as the anode, graphite as the cathode, and a cheap ionic liquid analog electrolyte made from a mixture of AlCl3 and urea in a 1.3:1 molar ratio. The battery displays discharge voltage plateaus around 1.9 and 1.5 V (average discharge = 1.73 V) and yielded a specific cathode capacity of ∼73 mAh g-1 at a current density of 100 mA g-1 (∼1.4 C). High Coulombic efficiency over a range of charge-discharge rates and stability over ∼150-200 cycles was easily demonstrated. In situ Raman spectroscopy clearly showed chloroaluminate anion intercalation/deintercalation of graphite (positive electrode) during charge-discharge and suggested the formation of a stage 2 graphite intercalation compound when fully charged. Raman spectroscopy and NMR suggested the existence of AlCl4-, Al2Cl7- anions and [AlCl2·(urea)n]+ cations in the AlCl3/urea electrolyte when an excess of AlCl3 was present. Aluminum deposition therefore proceeded through two pathways, one involving Al2Cl7- anions and the other involving [AlCl2·(urea)n]+ cations. This battery is a promising prospect for a future high-performance, low-cost energy storage device.
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Gossenberger F, Roman T, Forster-Tonigold K, Groß A. Change of the work function of platinum electrodes induced by halide adsorption. Beilstein J Nanotechnol 2014; 5:152-61. [PMID: 24605280 PMCID: PMC3943700 DOI: 10.3762/bjnano.5.15] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2013] [Accepted: 01/21/2014] [Indexed: 05/02/2023]
Abstract
The properties of a halogen-covered platinum(111) surface have been studied by using density functional theory (DFT), because halides are often present at electrochemical electrode/electrolyte interfaces. We focused in particular on the halogen-induced work function change as a function of the coverage of fluorine, chlorine, bromine and iodine. For electronegative adsorbates, an adsorption-induced increase of the work function is usually expected, yet we find a decrease of the work function for Cl, Br and I, which is most prominent at a coverage of approximately 0.25 ML. This coverage-dependent behavior can be explained by assuming a combination of charge transfer and polarization effects on the adsorbate layer. The results are contrasted to the adsorption of fluorine on calcium, a system in which a decrease in the work function is also observed despite a large charge transfer to the halogen adatom.
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Affiliation(s)
| | - Tanglaw Roman
- Institute of Theoretical Chemistry, Ulm University, 89069 Ulm, Germany
| | | | - Axel Groß
- Institute of Theoretical Chemistry, Ulm University, 89069 Ulm, Germany
- Helmholtz Institute Ulm (HIU) for Electrochemical Energy Storage, 89069 Ulm, Germany
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Jacquemin M, Genet MJ, Gaigneaux EM, Debecker DP. Calibration of the X-ray photoelectron spectroscopy binding energy scale for the characterization of heterogeneous catalysts: is everything really under control? Chemphyschem 2013; 14:3618-26. [PMID: 24009131 DOI: 10.1002/cphc.201300411] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Indexed: 11/10/2022]
Abstract
Investigations of X-ray photoelectron spectra from solid samples need corrections for the surface charging effect. For powder samples such as heterogeneous catalysts and their supports, the C-(C,H) component of the C 1s peak is often used as an internal standard for the calibration of the binding energy scale. Although this method is widely recognized as suitable for the study of heterogeneous catalysts, we show that a significant calibration bias can be encountered upon comparing samples with different bulk composition. In this paper, a series of SiO2-Al2O3 supports and Pd/SiO2-Al2O3 catalysts with various Si/Al ratios were studied. The spectra issued from these samples were processed with the classical calibration method on the basis of the carbon peak. Important discrepancies in the relative position of the photoelectron peaks were noticed. After systematically discarding instrument-related issues, a true chemical influence of the bulk matrix on the analyzed surface species was evidenced. The extent of this chemical effect was dependent on the composition of the sample and more precisely on its ionicity. Two possible mechanisms for this chemical effect were proposed and discussed. Finally, an alternative calibration method was offered.
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Affiliation(s)
- Marc Jacquemin
- Institute of Condensed Matter and Nanosciences (IMCN), Molecules, Solids and Reactivity (MOST), Université catholique de Louvain, Croix du Sud 2/L7.05.17, 1348 Louvain-la-Neuve (Belgium)
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