29 results on '"Matthew T. Dunstan"'
Search Results
2. Strongly coloured thiocyanate frameworks with perovskite-analogue structures
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Michael De Volder, Andrew J. Morris, Matthew J. Cliffe, Shahab Ahmad, Clare P. Grey, Evan N. Keyzer, Felix Deschler, and Matthew T. Dunstan
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Prussian blue ,Materials science ,Thiocyanate ,010405 organic chemistry ,Band gap ,Cyanide ,General Chemistry ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Chemistry ,chemistry.chemical_compound ,Crystallography ,chemistry ,Photocatalysis ,Absorption (chemistry) ,Topology (chemistry) ,Perovskite (structure) - Abstract
We report the first examples of thiocyanate-based analogues of the cyanide Prussian blue compounds, MIII[Bi(SCN)6], M = Fe, Cr, Sc., We report the first examples of thiocyanate-based analogues of the cyanide Prussian blue compounds, MIII[Bi(SCN)6], M = Fe, Cr, Sc. These compounds adopt the primitive cubic pcu topology and show strict cation order. Optical absorption measurements show these compounds have band gaps within the visible and near IR region, suggesting that they may be useful for applications where light harvesting is key, such as photocatalysis. We also show that Cr[Bi(SCN)6] can reversibly uptake water into its framework structure pointing towards the possibility of using these frameworks for host/guest chemistry.
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- 2019
3. CO2 capture using solid sorbents: Fundamental aspects, mechanistic insights and recent advances
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Matthew T. Dunstan, Felix Donat, Alexander H. Bork, Clare P. Grey, and Christoph R. Müller
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engrXiv|Engineering ,bepress|Engineering ,bepress|Engineering|Materials Science and Engineering|Other Materials Science and Engineering ,engrXiv|Engineering|Materials Science and Engineering|Other Materials Science and Engineering ,bepress|Engineering|Chemical Engineering ,bepress|Engineering|Materials Science and Engineering ,engrXiv|Engineering|Materials Science and Engineering ,engrXiv|Engineering|Chemical Engineering - Abstract
Carbon dioxide capture and mitigation forms a key part of the technological response to combat climate change and reduce CO2 emissions. Solid materials capable of reversibly absorbing CO2 have been the focus of intense research for the past two decades, promising stability and low energy costs to implement and operate compared to the more widely used liquid amines. In this Review, we explore the fundamental aspects underpinning solid CO2 sorbents based on alkali and alkaline earth metal oxides operating at mid- to high temperature: how their structure, chemical composition and morphology impact their performance and long-term use. Various optimization strategies are outlined to improve upon the most promising materials, and we combine recent advances across disparate scientific disciplines including materials discovery, synthesis, and in situ characterization to present a coherent understanding of the mechanisms of CO2 absorption both at surfaces and within solid materials.
- Published
- 2021
4. Exploring Cation-Anion Redox Processes in One-Dimensional Linear Chain Vanadium Tetrasulfide Rechargeable Magnesium Ion Cathodes
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Sylvia Britto, Sunita Dey, Jeongjae Lee, Clare P. Grey, Joshua M. Stratford, Matthew T. Dunstan, Mahmoud Elgaml, Giannantonio Cibin, Evan N. Keyzer, Simon J. Cassidy, Dey, Sunita [0000-0002-6601-7169], Dunstan, Matthew T [0000-0002-6319-4231], Grey, Clare P [0000-0001-5572-192X], and Apollo - University of Cambridge Repository
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34 Chemical Sciences ,Intercalation (chemistry) ,Inorganic chemistry ,Vanadium ,chemistry.chemical_element ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Redox ,Catalysis ,Cathode ,4016 Materials Engineering ,0104 chemical sciences ,law.invention ,Ion ,Colloid and Surface Chemistry ,chemistry ,Chain (algebraic topology) ,law ,3406 Physical Chemistry ,Magnesium ion ,40 Engineering - Abstract
For magnesium ion batteries (MIBs) to be used commercially, new cathodes must be developed that show stable reversible Mg intercalation. VS4 is one such promising material, with vanadium and disulfide anions [S2]2- forming one-dimensional linear chains, with a large interchain spacing (5.83 Å) enabling reversible Mg insertion. However, little is known about the details of the redox processes and structural transformations that occur upon Mg intercalation and deintercalation. Here, employing a suite of local structure characterization methods including X-ray photoelectron spectroscopy (XPS), V and S X-ray absorption near-edge spectroscopy (XANES), and 51V Hahn echo and magic-angle turning with phase-adjusted sideband separation (MATPASS) NMR, we show that the reaction proceeds via internal electron transfer from V4+ to [S2]2-, resulting in the simultaneous and coupled oxidation of V4+ to V5+ and reduction of [S2]2- to S2-. We report the formation of a previously unknown intermediate in the Mg-V-S compositional space, Mg3V2S8, comprising [VS4]3- tetrahedral units, identified by using density functional theory coupled with an evolutionary structure-predicting algorithm. The structure is verified experimentally via X-ray pair distribution function analysis. The voltage associated with the competing conversion reaction to form MgS plus V metal directly is similar to that of intermediate formation, resulting in two competing reaction pathways. Partial reversibility is seen to re-form the V5+ and S2- containing intermediate on charging instead of VS4. This work showcases the possibility of developing a family of transition metal polychalcogenides functioning via coupled cationic-anionic redox processes as a potential way of achieving higher capacities for MIBs.
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- 2020
- Full Text
- View/download PDF
5. Exploring the Peierls-Distorted Vanadium Sulphide as A Rechargeable Mg-Ion Cathod .pdf
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Jeongjae Lee, Sunita Dey, Clare P. Grey, Sylvia Britto, Mahmoud Elgaml, Evan N. Keyzer, Giannantonio Cibin, Simon J. Cassidy, Matthew T. Dunstan, and Joshua M. Stratford
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Electron transfer ,Crystallography ,Magic angle ,Materials science ,Solid-state nuclear magnetic resonance ,chemistry ,Transition metal ,Intercalation (chemistry) ,Vanadium ,chemistry.chemical_element ,Magnesium ion ,Redox - Abstract
For magnesium ion batteries (MIB) to be used commercially, new cathodes must be developed that show stable reversible Mg intercalation. VS4 is one such promising material, with vanadium and disulphide anions [S2]2- forming one dimensional linear chains, with a large interlayer spacing (5.83 Å) enabling Mg insertion. However, little is known about the details of the redox processes and structural transformations that occur upon Mg intercalation and deintercalation of VS4. Here we use a suite of local structure characterization methods including XPS, V and S X-ray Absorption Near Edge Spectroscopy and 51V Hahn-Echo and Magic Angle Turning with Phase Adjusted Sideband Separation NMR to elucidate the complex electrochemical reaction pathways. We show that the reaction proceeds via internal electron transfer from V4+ to [S2]2, resulting in the simultaneous and coupled oxidation of V4+ to V5+ and reduction of [S2]2- to S2-. We report the formation of a previously unknown intermediate in the Mg-V-S compositional space, Mg3V2S8, which is made of [VS4]3- tetrahedral units and identified using an evolutionary structure predicting algorithm and verified experimentally via X-ray Pair Distribution Function analysis. Subsequent magnesiation gives rise to the reduction of V5+ towards V4+. Further magnesiation sees conversion to MgS plus V metal; this reaction potential is close to the conversion potential of VS4 to Mg3V2S8, leading to competing reaction pathways. Demagnesiation results in the reformation of the V5+, S2- containing intermediate instead of VS4. This work showcases the possibility of developing a family of transition metal polychalcogenides functioning via anionic as well as combined cationic-anionic redox processes, as a potential way of achieving higher capacities for MIBs.
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- 2020
6. Study of Defect Chemistry in the System La2–xSrxNiO4+δ by 17O Solid-State NMR Spectroscopy and Ni K-Edge XANES
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Matthew T. Dunstan, Sylvia Britto, Clare P. Grey, David M. Halat, and Michael W. Gaultois
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Fermi contact interaction ,Chemistry ,General Chemical Engineering ,Analytical chemistry ,Ionic bonding ,02 engineering and technology ,General Chemistry ,Nuclear magnetic resonance spectroscopy ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,XANES ,0104 chemical sciences ,Solid-state nuclear magnetic resonance ,Materials Chemistry ,Ionic conductivity ,0210 nano-technology ,Spectroscopy ,Hyperfine structure - Abstract
The properties of mixed ionic–electronic conductors (MIECs) are most conveniently controlled through site-specific aliovalent substitution, yet few techniques can report directly on the local structure and defect chemistry underpinning changes in ionic and electronic conductivity. In this work, we perform high-resolution 17O (I = 5/2) solid-state NMR spectroscopy of La2–xSrxNiO4+δ, an MIEC and prospective solid oxide fuel cell (SOFC) cathode material, showing the sensitivity of 17O hyperfine (Fermi contact) shifts and quadrupolar coupling constants due to local structural changes arising from Sr substitution (x). Previously, we resolved resonances from three distinct oxygen sites (interstitial, axial, and equatorial) in the unsubstituted x = 0 material (Halat et al., J. Am. Chem. Soc. 2016, 138, 11958). Here, substitution-induced changes in these three spectral features indirectly report on the ionic conductivity, local octahedral tilting, and electronic conductivity, respectively, of the (substituted) ma...
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- 2018
7. Variable-temperature multinuclear solid-state NMR study of oxide ion dynamics in fluorite-type bismuth vanadate and phosphate solid electrolytes
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Clare P. Grey, Ivana Radosavljevic Evans, Matthew T. Dunstan, Matthew L. Tate, David M. Halat, Dunstan, MT [0000-0002-6319-4231], Halat, DM [0000-0002-0919-1689], Evans, IR [0000-0002-0325-7229], Grey, CP [0000-0001-5572-192X], and Apollo - University of Cambridge Repository
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3403 Macromolecular and Materials Chemistry ,Materials science ,34 Chemical Sciences ,General Chemical Engineering ,Oxide ,Ionic bonding ,02 engineering and technology ,General Chemistry ,Nuclear magnetic resonance spectroscopy ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,chemistry.chemical_compound ,Solid-state nuclear magnetic resonance ,chemistry ,Chemical physics ,Bismuth vanadate ,Vacancy defect ,3406 Physical Chemistry ,Materials Chemistry ,Fast ion conductor ,Ionic conductivity ,0210 nano-technology - Abstract
Ionic-conducting materials are crucial for the function of many advanced devices used in a variety of applications, such as fuel cells and gas separation membranes. Many different chemical controls, such as aliovalent doping, have been attempted to stabilise δ-Bi2O3, a material with exceptionally high oxide ion conductivity which is unfortunately only stable over a narrow temperature range. In this study, we employ a multinuclear, variable-temperature NMR spectroscopy approach to characterise and measure oxide ionic motion in the V- and P-substituted bismuth oxide materials Bi0.913V0.087O1.587, Bi0.852V0.148O1.648 and Bi0.852P0.148O1.648, previously shown to have excellent ionic conduction properties (Kuang et al., Chem. Mater. 2012, 24, 2162; Kuang et al., Angew. Chem. Int. Ed. 2012, 51, 690). Two main 17O NMR resonances are distinguished for each material, corresponding to O in the Bi–O and V–O/P–O sublattices. Using variable-temperature (VT) measurements ranging from room temperature to 923 K, the ionic motion experienced by these different sites has then been characterised, with coalescence of the two environments in the V-substituted materials clearly indicating a conduction mechanism facilitated by exchange between the two sublattices. The lack of this coalescence in the P-substituted material indicates a different mechanism, confirmed by 17O T1 (spin-lattice relaxation) NMR experiments to be driven purely by vacancy motion in the Bi–O sublattice. 51V and 31P VT-NMR experiments show high rates of tetrahedral rotation even at room temperature, increasing with heating. An additional VO4 environment appears in 17O and 51V NMR spectra of the more highly V-substituted Bi0.852V0.148O1.648, which we ascribe to differently distorted VO4 tetrahedral units that disrupt the overall ionic motion, consistent both with linewidth analysis of the 17O VT-NMR spectra and experimental results of Kuang et al. showing a lower oxide ionic conductivity in this material compared to Bi0.913V0.087O1.587 (Chem. Mater. 2012, 24, 2162). This study shows solid-state NMR is particularly well suited to understanding connections between local structural features and ionic mobility, and can quantify the evolution of oxide-ion dynamics with increasing temperature.
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- 2019
8. Synthesis, Application, and Carbonation Behavior of Ca2Fe2O5 for Chemical Looping H2 Production
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Stuart A. Scott, Mohammad Ismail, Martin S. C. Chan, Wen Liu, Matthew T. Dunstan, Dunstan, Matthew [0000-0002-6319-4231], and Apollo - University of Cambridge Repository
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Thermogravimetric analysis ,Hydrogen ,Coprecipitation ,020209 energy ,General Chemical Engineering ,4004 Chemical Engineering ,Iron oxide ,Energy Engineering and Power Technology ,chemistry.chemical_element ,02 engineering and technology ,021001 nanoscience & nanotechnology ,chemistry.chemical_compound ,Fuel Technology ,chemistry ,Chemical engineering ,Ferrite (iron) ,0202 electrical engineering, electronic engineering, information engineering ,Organic chemistry ,7 Affordable and Clean Energy ,0210 nano-technology ,Calcium oxide ,Chemical looping combustion ,40 Engineering ,Hydrogen production - Abstract
Chemical looping hydrogen production uses the oxidation and reduction of metal oxides, typically iron, to produce hydrogen. This work focuses on the modification of iron oxide with calcium oxide to form an oxygen carrier containing dicalcium ferrite (Ca2Fe2O5), which presents favorable thermodynamics for achieving higher conversions of steam to hydrogen, compared to chemically unmodified iron oxide. Different methods of synthesis, viz. mechanochemical synthesis and coprecipitation, were used to produce Ca2Fe2O5, and their resulting performances were compared. Consistent with thermodynamic predictions, it was found that CO2, or steam, was sufficient to fully regenerate the reduced carriers to Ca2Fe2O5. The cyclic stability of the oxygen carriers were studied in fluidized bed reactors and by thermogravimetric analysis (TGA). Good stability of the materials was observed for up to 50 cycles, with no evidence of agglomeration, even up to 950 °C. The rate of deactivation was found to correlate with the purity of Ca2Fe2O5 and the presence of impurity phases such as CaFe2O4, which had a tendency to segregate into its constituent elemental oxides. Carbonation of the oxygen carriers was examined by TGA, and it was found to occur appreciably only for the reduced carrier (a mixture of CaO and Fe) between temperatures of 500-700 °C and 0.1-0.5 atm of CO2, whereas the oxidized carrier (viz. Ca2Fe2O5) did not carbonate. Fresh and cycled materials were characterized by XRD, SEM, and BET analysis. Ca2Fe2O5 is a potentially viable material as an oxygen carrier for hydrogen production; however, because of thermodynamic limitations, it cannot be used for complete fuel oxidation.
- Published
- 2016
9. Large scale computational screening and experimental discovery of novel materials for high temperature CO2 capture
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Stuart A. Scott, Kristin A. Persson, Clare P. Grey, Wen Liu, John S. Dennis, Shyue Ping Ong, Jeongjae Lee, Anubhav Jain, Matthew T. Dunstan, Tao Liu, Dunstan, Matthew [0000-0002-6319-4231], Lee, Jeongjae [0000-0003-4294-4993], Dennis, John [0000-0002-5014-5676], Grey, Clare [0000-0001-5572-192X], and Apollo - University of Cambridge Repository
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Engineering ,Power station ,Process (engineering) ,New materials ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,4016 Materials Engineering ,Lower energy ,Environmental Chemistry ,Process engineering ,Simulation ,40 Engineering ,13 Climate Action ,34 Chemical Sciences ,Renewable Energy, Sustainability and the Environment ,business.industry ,Scale (chemistry) ,021001 nanoscience & nanotechnology ,Pollution ,0104 chemical sciences ,Nuclear Energy and Engineering ,Work (electrical) ,Software deployment ,Co2 absorption ,7 Affordable and Clean Energy ,0210 nano-technology ,business - Abstract
© 2016 The Royal Society of Chemistry. The implementation of large-scale carbon dioxide capture and storage (CCS) is dependent on finding materials that satisfy several different criteria, the most important being minimising the energy load imposed on the power plant to run the process. The most mature CCS technology, amine scrubbing, leads to a loss of 30% of the electrical work output of the power station without capture, which is far too high for widespread deployment. High-temperature CO2absorption looping has emerged as a technology that has the potential to deliver much lower energy penalties, but further work is needed to find and develop an optimal material. We have developed a combined computational and experimental methodology to predict new materials that should have desirable properties for CCS looping, and then select promising candidates to experimentally validate these predictions. This work not only has discovered novel materials for use in high-temperature CCS looping, but analysis of the entirety of the screening enables greater insights into new design strategies for future development.
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- 2016
10. CCS – A technology for now: general discussion
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Andac Armutlulu, Liya Zheng, Matthew T. Dunstan, Niall MacDowell, Patrick Brandl, Jon Gibbins, Paul S. Fennell, George Dowson, Joshuah K. Stolaroff, Peter Styring, Berend Smit, Grant W. Wilson, Marco Mazzotti, Rahul Anantharaman, Stephen Matthew Lyth, Kyra Sedransk Campbell, Geoffrey C. Maitland, María Erans, Raffaella Ocone, Christoph R. Müller, Jet-Sing M. Lee, Martin Trusler, Daniel Sutter, Thomas Hills, Gary T. Rochelle, Joseph G. Yao, Stefano Brandani, Peter T. Clough, John Blamey, and Matteo Gazzani
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010405 organic chemistry ,Environmental science ,Physical and Theoretical Chemistry ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences - Published
- 2016
11. A high temperature gas flow environment for neutron total scattering studies of complex materials
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S. Michelle Everett, Rebecca Mills, Jue Liu, Matthew T. Dunstan, Katharine Page, Daniel Olds, Marshall T. McDonnell, Joshua R. Kim, Matthew G. Tucker, and Michael W. Gaultois
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Materials science ,Scattering ,Carbonation ,Neutron diffraction ,Pair distribution function ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Chemical physics ,Neutron ,0210 nano-technology ,Inert gas ,Instrumentation ,Spallation Neutron Source ,Diffractometer - Abstract
We present the design and capabilities of a high temperature gas flow environment for neutron diffraction and pair distribution function studies available at the Nanoscale Ordered Materials Diffractometer instrument at the Spallation Neutron Source. Design considerations for successful total scattering studies are discussed, and guidance for planning experiments, preparing samples, and correcting and reducing data is defined. The new capabilities are demonstrated with an in situ decomposition study of a battery electrode material under inert gas flow and an in operando carbonation/decarbonation experiment under reactive gas flow. This capability will aid in identifying and quantifying the atomistic configurations of chemically reactive species and their influence on underlying crystal structures. Furthermore, studies of reaction kinetics and growth pathways in a wide variety of functional materials can be performed across a range of length scales spanning the atomic to the nanoscale.
- Published
- 2018
12. Screening and characterization of ternary oxides for high temperature carbon capture
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Martin S. C. Chan, Clare P. Grey, Matthew T. Dunstan, Michael W. Gaultois, and Adam W. Bateson
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Metal ,Alkaline earth metal ,Materials science ,Chemical engineering ,Transition metal ,visual_art ,visual_art.visual_art_medium ,Sorption ,Crystal structure ,Alkali metal ,Ternary operation ,Ion - Abstract
This work describes the experimental characterisation and CO2 sorption properties of several new ternary transition metal oxides predicted by high-throughput DFT screening. One material reported here, Li5SbO5, displays reversible CO2 sorption, and maintains ~72% of its theoretical capacity out to 25 cycles. The results in this work are used to discuss major influences on CO2 absorption capacity and rate, including the role of the crystal structure, the transition metal, the alkali or alkaline earth metal, and the competing roles of thermodynamics and kinetics. Notably, this work shows the extent and rate to which ternary metal oxides carbonate is driven primarily by the identity of the alkali or alkaline earth ion and the nature of the crystal structure, whereas the identity of the transition ion carries little influence in the systems studied here.
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- 2018
13. Screening and Characterization of Ternary Oxides for High-Temperature Carbon Capture
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Matthew T. Dunstan, Martin S. C. Chan, Clare P. Grey, Michael W. Gaultois, Adam W. Bateson, Gaultois, MW [0000-0003-2172-2507], Dunstan, MT [0000-0002-6319-4231], Chan, MSC [0000-0002-3362-6662], Grey, CP [0000-0001-5572-192X], and Apollo - University of Cambridge Repository
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Work (thermodynamics) ,13 Climate Action ,Materials science ,34 Chemical Sciences ,Component (thermodynamics) ,General Chemical Engineering ,Sorption ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Alkali metal ,01 natural sciences ,0104 chemical sciences ,Characterization (materials science) ,3402 Inorganic Chemistry ,Transition metal ,Chemical engineering ,13. Climate action ,Materials Chemistry ,Carbon capture and storage ,0210 nano-technology ,Ternary operation - Abstract
Carbon capture and storage (CCS) is increasingly being accepted as a necessary component of any effort to mitigate the impact of anthropogenic climate change, as it is both a relatively mature and easily implemented technology. High-temperature CO2 absorption looping is a promising process that offers a much lower energy penalty than the current state of the art amine scrubbing techniques, but more effective materials are required for widespread implementation. This work describes the experimental characterisation and CO2 absorption properties of several new ternary transition metal oxides predicted by high-throughput DFT screening. One material reported here, Li5SbO5, displays reversible CO2 sorption, and maintains 72 % of its theoretical capacity out to 25 cycles. The results in this work are used to discuss major influences on CO2 absorption capacity and rate, including the role of the crystal structure, the transition metal, the alkali or alkaline earth metal, and the competing roles of thermodynamics and kinetics. Notably, this work shows the extent and rate to which ternary metal oxides carbonate is driven primarily by the identity of the alkali or alkaline earth ion and the nature of the crystal structure, whereas the identity of the transition ion carries little influence in the systems studied here.
- Published
- 2018
14. High-throughput DFT screening and experimental characterization of ternary oxides for high temperature carbon capture and storage
- Author
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Martin S. C. Chan, Adam W. Bateson, Michael W. Gaultois, Matthew T. Dunstan, and Clare P. Grey
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Metal ,Alkaline earth metal ,Materials science ,Chemical engineering ,Transition metal ,visual_art ,visual_art.visual_art_medium ,Sorption ,Crystal structure ,Alkali metal ,Ternary operation ,Ion - Abstract
This work describes the experimental characterisation and CO2 sorption properties of several new ternary transition metal oxides predicted by high-throughput DFT screening. One material reported here, Li5SbO5, displays reversible CO2 sorption, and maintains ~72% of its theoretical capacity out to 25 cycles. The results in this work are used to discuss major influences on CO2 absorption capacity and rate, including the role of the crystal structure, the transition metal, the alkali or alkaline earth metal, and the competing roles of thermodynamics and kinetics. Notably, this work shows the extent and rate to which ternary metal oxides carbonate is driven primarily by the identity of the alkali or alkaline earth ion and the nature of the crystal structure, whereas the identity of the transition ion carries little influence in the systems studied here.
- Published
- 2017
15. Ion Dynamics in Li2CO3 Studied by Solid-State NMR and First-Principles Calculations
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Frédéric Blanc, John M. Griffin, Clare P. Grey, Michal Leskes, and Matthew T. Dunstan
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Chemistry ,chemistry.chemical_element ,Activation energy ,Atmospheric temperature range ,7. Clean energy ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Ion ,General Energy ,Solid-state nuclear magnetic resonance ,Chemical physics ,Phase (matter) ,Carbonate Ion ,Physical chemistry ,Reactivity (chemistry) ,Lithium ,Physical and Theoretical Chemistry - Abstract
Novel lithium-based materials for carbon capture and storage (CCS) applications have emerged as a promising class of materials for use in CO2 looping, where the material reacts reversibly with CO2 to form Li2CO3, among other phases depending on the parent phase. Much work has been done to try and understand the origin of the continued reactivity of the process even after a layer of Li2CO3 has covered the sorbent particles. In this work, we have studied the lithium and oxygen ion dynamics in Li2CO3 over the temperature range of 293–973 K in order to elucidate the link between dynamics and reactivity in this system. We have used a combination of powder X-ray diffraction, solid-state NMR spectroscopy, and theoretical calculations to chart the temperature dependence of both structural changes and ion dynamics in the sample. These methods together allowed us to determine the activation energy for both lithium ion hopping processes and carbonate ion rotations in Li2CO3. Importantly, we have shown that these pro...
- Published
- 2015
16. Local Structure and Dynamics in the Na Ion Battery Positive Electrode Material Na3V2(PO4)2F3
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Clare P. Grey, Yan-Yan Hu, Matthew T. Dunstan, Yong Yang, Xiaogang Hao, Huan Zou, Hua Huo, Zigeng Liu, and Guiming Zhong
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NMR spectra database ,Unpaired electron ,Chemistry ,General Chemical Engineering ,Electrode ,Materials Chemistry ,Analytical chemistry ,Ionic bonding ,General Chemistry ,Nuclear magnetic resonance spectroscopy ,Electrochemistry ,Hyperfine structure ,Ion - Abstract
Na3V2(PO4)2F3 is a novel electrode material that can be used in both Li ion and Na ion batteries (LIBs and NIBs). The long- and short-range structural changes and ionic and electronic mobility of Na3V2(PO4)2F3 as a positive electrode in a NIB have been investigated with electrochemical analysis, X-ray diffraction (XRD), and high-resolution 23 Na and 31 P solid-state nuclear magnetic resonance (NMR). The 23 Na NMR spectra and XRD refinements show that the Na ions are removed non- selectively from the two distinct Na sites, the fully occupied Na1 site and the partially occupied Na2 site, at least at the beginning of charge. Anisotropic changes in lattice parameters of the cycled Na3V2(PO4)2F3 electrode upon charge have been observed, where a (= b) continues to increase and c decreases, indicative of solid-solution processes. A noticeable decrease in the cell volume between 0.6 Na and 1 Na is observed along with a discontinuity in the 23 Na hyperfine shift between 0.9 and 1.0 Na extraction, which we suggest is due to a rearrangement of unpaired electrons within the vanadium t2g orbitals. The Na ion mobility increases steadily on charging as more Na vacancies are formed, and coalescence of the resonances from the two Na sites is observed when 0.9 Na is removed, indicating a Na1−Na2 hopping (two-site exchange) rate of ≥4.6 kHz. This rapid Na motion must in part be responsible for the good rate performance of this electrode material. The 31 P NMR spectra are complex, the shifts of the two crystallograpically distinct sites being sensitive to both local Na cation ordering on the Na2 site in the as-synthesized material, the presence of oxidized (V 4+ ) defects in the structure, and the changes of cation and electronic mobility on Na extraction. This study shows how NMR spectroscopy complemented by XRD can be used to provide insight into the mechanism of Na extraction from Na3V2(PO4)2F3 when used in a NIB.
- Published
- 2014
17. Reversible CO2 Absorption by the 6H Perovskite Ba4Sb2O9
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Adriano F. Pavan, Stuart A. Scott, Justin A. Kimpton, Matthew T. Dunstan, Clare P. Grey, John S. Dennis, Wen Liu, and Chris D. Ling
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Thermogravimetric analysis ,Sorbent ,Materials science ,General Chemical Engineering ,Carbonation ,Mineralogy ,General Chemistry ,Chemical reaction ,Crystallography ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Structural Biology ,X-ray crystallography ,Materials Chemistry ,Barium carbonate ,Absorption (chemistry) ,Perovskite (structure) - Abstract
A novel compound for carbon capture and storage (CCS) applications, the 6H perovskite Ba4Sb2O9, was found to be able to absorb CO2 through a chemical reaction at 873 K to form barium carbonate and BaSb2O6. This absorption was shown to be reversible through the regeneration of the original Ba4Sb2O9 material upon heating above 1223 K accompanied by the release of CO2. A combined synchrotron X-ray diffraction, thermogravimetric, and microscopy study was carried out to characterize first the physical absorption properties and then to analyze the structural evolution and formation of phases in situ. Importantly, through subsequent carbonation and regeneration of the material over 100 times, it was shown that the combined absorption and regeneration reactions proceed without any significant reduction in the CO2 absorption capacity of the material. After 100 cycles the capacity of Ba4Sb2O9 was ∼0.1 g (CO2)/g (sorbent), representing 73% of the total molar capacity. This is the first report of a perovskite-type ma...
- Published
- 2013
18. Theoretical and experimental screening methods for functional materials design
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Clare P. Grey, John S. Dennis, Matthew T. Dunstan, Cindy Y. Lau, Wenting Hu, Andrew J. Morris, Stuart A. Scott, and Can P. Koçer
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Inorganic Chemistry ,Structural Biology ,Computer science ,Screening method ,General Materials Science ,Biochemical engineering ,Physical and Theoretical Chemistry ,Materials design ,Condensed Matter Physics ,Biochemistry - Published
- 2017
19. Complex 5d Magnetism in a Novel S = 1/2 Trimer System, the 12L Hexagonal Perovskite Ba4BiIr3O12
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Matthew T. Dunstan, Zixin Huang, Zakiah Mohamed, Brendan J. Kennedy, Wojciech Miiller, Maxim Avdeev, and Chris D. Ling
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Inorganic Chemistry ,chemistry.chemical_compound ,Crystallography ,chemistry ,Octahedron ,Electrical resistivity and conductivity ,Magnetism ,Dimer ,Trimer ,Electron configuration ,Physical and Theoretical Chemistry ,Magnetic susceptibility ,Perovskite (structure) - Abstract
The 12L hexagonal perovskite Ba4BiIr3O12 has been synthesized for the first time and characterized using high-resolution neutron and synchrotron X-ray diffraction as well as physical properties measurements. The structure contains Ir3O12 linear face-sharing octahedral trimer units, bridged by corner-sharing BiO6 octahedra. The average electronic configurations of Ir and Bi are shown to be +4(d(5)) and +4(s(1)), respectively, the same as for the S = 1/2 dimer system Ba3BiIr2O9, which undergoes a spin-gap opening with a strong magnetoelastic effect at T* = 74 K. Anomalies in magnetic susceptibility, heat capacity, electrical resistivity, and unit cell parameters indeed reveal an analogous effect at T* ≈ 215 K in Ba4BiIr3O12. However, the transition is not accompanied by the opening of a gap in spin excitation spectrum, because antiferromagnetic coupling among S = 1/2 Ir(4+) (d(5)) cations leads to the formation of a S = 1/2 doublet within the trimers, vs S = 0 singlets within dimers. The change in magnetic state of the trimers at T* leads to a structural distortion, the energy of which is overcompensated for by the formation of S = 1/2 doublets. Extending this insight to the dimer system Ba3BiIr2O9 sheds new light on the more pronounced low-temperature anomalies observed for that compound.
- Published
- 2013
20. Long-Range-Ordered Coexistence of 4-, 5-, and 6-Coordinate Niobium in the Mixed Ionic-Electronic Conductor γ-Ba4Nb2O9
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Frédéric Blanc, Matthew T. Dunstan, Garry J. McIntyre, Maxim Avdeev, Chris D. Ling, and Clare P. Grey
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Materials science ,General Chemical Engineering ,Neutron diffraction ,Niobium ,Oxide ,chemistry.chemical_element ,Ionic bonding ,General Chemistry ,Crystallography ,chemistry.chemical_compound ,Solid-state nuclear magnetic resonance ,chemistry ,Materials Chemistry ,Ionic conductivity ,Superstructure (condensed matter) ,Perovskite (structure) - Abstract
In a study combining high-resolution single-crystal neutron diffraction and solid-state nuclear magnetic resonance, the mixed ionic-electronic conductor γ-Ba4Nb2O9 is shown to have a unique structure type, incorporating niobium in 4-, 5-, and 6-coordinate environments. The 4- and 5-coordinate niobium tetrahedra and trigonal bipyrimids exist in discrete layers, within and among which their orientations vary systematically to form a complex superstructure. Through analysis and comparison of data obtained from hydrated versus dehydrated samples, a mechanism is proposed for the ready hydration of the material by atmospheric water. This mechanism, and the resulting hydrated structure, help explain the high protonic and oxide ionic conductivity of γ-Ba4Nb2O9.
- Published
- 2013
21. Phase behavior and mixed ionic–electronic conductivity of Ba4Sb2O9
- Author
-
Vladislav V. Kharton, Maxim Avdeev, Justin A. Kimpton, Matthew T. Dunstan, Ekaterina V. Tsipis, Chris D. Ling, Adriano F. Pavan, and V.A. Kolotygin
- Subjects
Materials science ,Analytical chemistry ,TEMPERATURE PROTON CONDUCTIVITY ,Mineralogy ,Ionic bonding ,TRANSITIONS ,02 engineering and technology ,Conductivity ,CONDUCTORS ,010402 general chemistry ,01 natural sciences ,Ion ,Phase (matter) ,Formula unit ,0302 Inorganic Chemistry ,Ionic conductivity ,General Materials Science ,Perovskite (structure) ,NUMBERS ,STABILITY ,HYDRATION ,OXIDE ,General Chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,TRANSPORT ,0104 chemical sciences ,PEROVSKITES ,13. Climate action ,CERAMICS ,0210 nano-technology ,Monoclinic crystal system - Abstract
The 6H-type perovskite phase Ba4Sb2O9, which decomposes in air below 600 K, is found to survive to room temperature in a CO2-free atmosphere. It shows substantial mixed protonic, oxide ionic and electronic conductivity. Compared to Ba4Nb2O9 and Ba4Ta2O9, Ba4Sb2O9 shows higher ionic conductivity due to the relatively easy reducibility of Sb5+, but lower electronic conductivity due to the predominantly n-type conductivity provided by the Sb5+/Sb3+ redox couple which leads to reduced hole concentration under oxidizing conditions. Variable temperature synchrotron X-ray diffraction studies carried out in situ under controlled atmospheres reveal a strong monoclinic distortion below 1150 K. The hexagonal to monoclinic transition is slow, does not show second-order behavior, is strongly dependent on atmosphere, and coincides with the loss of similar to 0.4 molecules of H2O per formula unit of Ba4Sb2O9. All of this suggests an important structural role for protons or hydroxide ions in the monoclinic phase. (C) 2013 Elsevier B.V. All rights reserved.
- Published
- 2013
22. In situ studies of materials for high temperature CO
- Author
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Matthew T, Dunstan, Serena A, Maugeri, Wen, Liu, Matthew G, Tucker, Oluwadamilola O, Taiwo, Belen, Gonzalez, Phoebe K, Allan, Michael W, Gaultois, Paul R, Shearing, David A, Keen, Anthony E, Phillips, Martin T, Dove, Stuart A, Scott, John S, Dennis, and Clare P, Grey
- Abstract
Carbon capture and storage (CCS) offers a possible solution to curb the CO
- Published
- 2016
23. Phase diagram, chemical stability and physical properties of the solid-solution Ba4Nb2−Ta O9
- Author
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Cameron J. Kepert, James R. Hester, Peter D. Southon, Justin A. Kimpton, Chris D. Ling, and Matthew T. Dunstan
- Subjects
Phase transition ,Materials science ,Inorganic chemistry ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,Inorganic Chemistry ,Crystallography ,13. Climate action ,Impurity ,Phase (matter) ,Materials Chemistry ,Ceramics and Composites ,Chemical stability ,Physical and Theoretical Chemistry ,0210 nano-technology ,Hydrate ,Phase diagram ,Perovskite (structure) ,Solid solution - Abstract
Through the construction of the Ba4Nb2−xTaxO9 phase diagram, it was discovered that the unique high-temperature γ phase is a thermodynamic intermediate between the low-temperature α phase (Sr4Ru2O9-type) and a 6H-perovskite. Refined site occupancies for the γ phase across the Ba4Nb2−xTaxO9 solid-solution indicate that Nb preferentially occupies the tetrahedral sites over the octahedral sites in the structure. When annealed in a CO2-rich atmosphere, all of the phases studied absorb large amounts of CO2 at high temperatures between ∼ 700 and 1300 K. In situ controlled-atmosphere diffraction studies show that this behaviour is linked to the formation of BaCO3 on the surface of the material, accompanied by a Ba5(Nb,Ta)4O15 impurity phase. In situ diffraction in humid atmospheres also confirms that these materials hydrate below ∼ 1273 K , and that this plays a critical role in the various reconstructive phase transitions as well as giving rise to proton conduction.
- Published
- 2011
24. Antioxidant capacity and hydrophilic phytochemicals in commercially grown native Australian fruits
- Author
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Patricia Aguas, Izabela Konczak, Matthew T. Dunstan, and Dimitrios Zabaras
- Subjects
chemistry.chemical_classification ,Santalum acuminatum ,food.ingredient ,biology ,Chemistry ,food and beverages ,General Medicine ,biology.organism_classification ,Ascorbic acid ,Analytical Chemistry ,chemistry.chemical_compound ,Flavonols ,food ,Botany ,Davidsonia pruriens ,Phenols ,Food science ,KAKADU PLUM ,Acronychia acidula ,Citrus australasica ,Food Science - Abstract
Hydrophilic phytochemicals and antioxidant capacities of eight commercially grown native Australian fruits were determined. Kakadu plum (Terminalia ferdinandiana) contained a 6-fold higher level of total phenolic compounds and quandong (Santalum acuminatum) a 1.9-fold higher level of total phenolic compounds (TP, Folin–Ciocalteu assay) than blueberry (Vaccinum sp., cv. Biloxi). Both fruits displayed superior oxygen radical-scavenging capacity (ORAC-H assay) that was, respectively 4.1-fold and 6.5-fold of that of blueberry. The total reducing capacity (TRC; ferric reducing antioxidant power (FRAP) assay) of Kakadu plum and quandong exceeded the TRC of blueberry, respectively, 13.1- and 2.3-times. The primary sources of antioxidant capacities in the evaluated fruits were phenolic acids (benzoic and cinnamic) and flavonoids (flavonols, flavanones and anthocyanins) tentatively detected by liquid chromatography–mass spectrometry (LC–PDA–MS/MS). A high level of vitamin C was recorded for Kakadu plum and Australian citrus fruits. The major organic acids detected were citric and malic acid.
- Published
- 2010
25. ChemInform Abstract: Local Structure and Dynamics in the Na Ion Battery Positive Electrode Material Na3V2(PO4)2F3
- Author
-
Yan-Yan Hu, Hua Huo, Clare P. Grey, Xiaogang Hao, Zigeng Liu, Yong Yang, Matthew T. Dunstan, Guiming Zhong, and Huan Zou
- Subjects
Battery (electricity) ,chemistry.chemical_compound ,Electrode material ,Nanocomposite ,Argon ,chemistry ,Chemical engineering ,chemistry.chemical_element ,General Medicine ,Citric acid ,Local structure - Abstract
A VPO4/C nanocomposite is prepared as precursor by sol-gel processing of a 1:2:2 mixture of V2O5, H3PO4, and citric acid (heating of the dried gel under argon, 350 and 700 °C, 6 h each).
- Published
- 2014
26. ChemInform Abstract: Reversible CO2Absorption by the 6H Perovskite Ba4Sb2O9
- Author
-
Wen Liu, J. S. Dennis, Adriano F. Pavan, Chris D. Ling, Stuart A. Scott, Justin A. Kimpton, Clare P. Grey, and Matthew T. Dunstan
- Subjects
Chemical engineering ,law ,Chemistry ,Co2 absorption ,Calcination ,General Medicine ,Crystallite ,Stoichiometry ,law.invention ,Perovskite (structure) - Abstract
Polycrystalline Ba4Sb2O9 is prepared by calcination of a stoichiometric mixture of BaCO3 and Sb2O3 (1273 K, 2 d).
- Published
- 2014
27. ChemInform Abstract: Complex 5d Magnetism in a Novel S = 1/2 Trimer System, the 12L Hexagonal Perovskite Ba4BiIr3O12
- Author
-
Wojciech Miiller, Chris D. Ling, Zakiah Mohamed, Brendan J. Kennedy, Maxim Avdeev, Zixin Huang, and Matthew T. Dunstan
- Subjects
Metal ,Crystallography ,Hexagonal crystal system ,Magnetism ,Chemistry ,visual_art ,Inorganic chemistry ,Solid-state ,visual_art.visual_art_medium ,Trimer ,General Medicine ,Perovskite (structure) - Abstract
The title compound is prepared by solid state reaction of BaCO3, Bi2O3 (10% excess), and Ir metal (1173 K, 2 d).
- Published
- 2014
28. Origin of additional capacities in metal oxide lithium-ion battery electrodes
- Author
-
Peter J. Chupas, Karena W. Chapman, Kyung-Wan Nam, Olaf J. Borkiewicz, Xiao-Qing Yang, Yan-Yan Hu, Matthew T. Dunstan, Xiao Hua, Kamila M. Wiaderek, Jun Cheng, Lin-Shu Du, Zigeng Liu, Claire P. Grey, and Xiqian Yu
- Subjects
Battery (electricity) ,Materials science ,Mechanical Engineering ,Inorganic chemistry ,Intercalation (chemistry) ,Oxide ,General Chemistry ,Electrolyte ,Condensed Matter Physics ,Lithium-ion battery ,Reversible reaction ,Amorphous solid ,chemistry.chemical_compound ,Chemical engineering ,chemistry ,Mechanics of Materials ,Electrode ,General Materials Science - Abstract
Metal fluorides/oxides (MF(x)/M(x)O(y)) are promising electrodes for lithium-ion batteries that operate through conversion reactions. These reactions are associated with much higher energy densities than intercalation reactions. The fluorides/oxides also exhibit additional reversible capacity beyond their theoretical capacity through mechanisms that are still poorly understood, in part owing to the difficulty in characterizing structure at the nanoscale, particularly at buried interfaces. This study employs high-resolution multinuclear/multidimensional solid-state NMR techniques, with in situ synchrotron-based techniques, to study the prototype conversion material RuO2. The experiments, together with theoretical calculations, show that a major contribution to the extra capacity in this system is due to the generation of LiOH and its subsequent reversible reaction with Li to form Li2O and LiH. The research demonstrates a protocol for studying the structure and spatial proximities of nanostructures formed in this system, including the amorphous solid electrolyte interphase that grows on battery electrodes.
- Published
- 2013
29. In situstudies of materials for high-temperature CO2capture and storage
- Author
-
Serena Maugeri, Dami Taiwo, Martin T. Dove, Wen Liu, Clare P. Grey, John S. Dennis, Matthew T. Dunstan, Paul R. Shearing, Adriano F. Pavan, Chris D. Ling, and Stuart A. Scott
- Subjects
Inorganic Chemistry ,Structural Biology ,General Materials Science ,Physical and Theoretical Chemistry ,Condensed Matter Physics ,Biochemistry - Published
- 2015
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