David Stephen Wragg

• Gerz, Isabelle; Aunan, Erlend ; Finelli, Valeria; Abu Rasheed, Mouhammad; Deplano, Gabriele & Cortez Sgroi Pupo, Rafael [Vis alle 15 forfattere av denne artikkelen] (2024). Enabling a bioinspired N,N,N-copper coordination motif through spatial control in UiO-67: synthesis and reactivity. Dalton Transactions. ISSN 1477-9226. doi: 10.1039/d3dt03096b.
• Brennhagen, Anders; Skautvedt, Casper; Cavallo, Carmen; Wragg, David Stephen; Koposov, Alexey & Sjåstad, Anja Olafsen [Vis alle 7 forfattere av denne artikkelen] (2024). Unraveling the (De)sodiation Mechanisms of BiFeO<inf>3</inf> at a High Rate with Operando XRD. ACS Applied Materials & Interfaces. ISSN 1944-8244. 16(10), s. 12428–12436. doi: 10.1021/acsami.3c17296. Fulltekst i vitenarkiv Vis sammendrag

  Development of new anode materials for Na-ion batteries strongly depends on a detailed understanding of their cycling mechanism. Due to instrumental limitations, the majority of mechanistic studies focus on operando materials’ characterization at low cycling rates. In this work, we evaluate and compare the (de)sodiation mechanisms of BiFeO3 in Na-ion batteries at different current densities using operando X-ray diffraction (XRD) and ex situ X-ray absorption spectroscopy (XAS). BiFeO3 is a conversion-alloying anode material with a high initial sodiation capacity of ∼600 mAh g–1, when cycled at 0.1 A g–1. It does not change its performance or cycling mechanism, except for minor losses in capacity, when the current density is increased to 1 A g–1. In addition, operando XRD characterization carried out over multiple cycles shows that the Bi ⇋ NaBi (de)alloying reaction and the oxidation of Bi at the interface with the Na–Fe–O matrix are detrimental for cycling stability. The isolated NaBi ⇋ Na3Bi reaction is less damaging to the cycling stability of the material.

• Park, Heesoo; Wragg, David Stephen & Koposov, Alexey (2024). Replica exchange molecular dynamics for Li-intercalation in graphite: a new solution for an old problem. Chemical Science. ISSN 2041-6520. doi: 10.1039/d3sc06107h. Fulltekst i vitenarkiv Vis sammendrag

  Li intercalation and graphite stacking have been extensively studied because of the importance of graphite in commercial Li-ion batteries. Despite this attention, there are still questions about the atomistic structures of the intermediate states that exist during lithiation, especially when phase dynamics cause a disordered Li distribution. The Li migration event (diffusion coefficient of 10−5 nm2 ns−1) makes it difficult to explore the various Li-intercalation configurations in conventional molecular dynamics (MD) simulations with an affordable simulation timescale. To overcome these limitations, we conducted a comprehensive study using replica-exchange molecular dynamics (REMD) in combination with the ReaxFF force field. This approach allowed us to study the behavior of Li-intercalated graphite from any starting arrangement of Li at any value of x in LixC6. Our focus was on analyzing the energetic favorability differences between the relaxed structures. We rationalized the trends in formation energy on the basis of observed structural features, identifying three main structural features that cooperatively control Li rearrangement in graphite: Li distribution, graphite stacking mode and gallery height (graphene layer spacing). We also observed a tendency for clustering of Li, which could lead to dynamic local structures that approximate the staging models used to explain intercalation into graphite.

• Yartys, Volodymyr; Denys, Roman Volodymyrovich; Akselrud, Lev G.; Ponniah, Vajeeston; Dankelman, Robert & Plomp, Jeroen [Vis alle 11 forfattere av denne artikkelen] (2024). Structure and bonding in TiNiSi type LaMgSnH intermetallic hydride. Journal of Alloys and Compounds. ISSN 0925-8388. 976. doi: 10.1016/j.jallcom.2023.173198. Fulltekst i vitenarkiv
• Wragg, David Stephen; Skautvedt, Casper; Brennhagen, Anders; Geiss, Carina; Checchia, Stefano & Koposov, Alexey (2023). Tracking Lithiation of Si-Based Anodes in Real Time by Total Scattering Computed Tomography. Journal of Physical Chemistry C. ISSN 1932-7447. 127(48), s. 23149–23155. doi: 10.1021/acs.jpcc.3c06414. Fulltekst i vitenarkiv
• Lundegaard, Lars Fahl; Capel Berdiell, Izar; König, Nico; Haaber Junge, Nicolai; Beato, Pablo & Chernyshov, Dmitry [Vis alle 8 forfattere av denne artikkelen] (2023). Tracking deactivation of zeolite beta with and without a detailed structure model: XRD analysis and in situ studies. Microporous and Mesoporous Materials. ISSN 1387-1811. 366. doi: 10.1016/j.micromeso.2023.112911.
• Monasterial, Abigale P.; Weddle, Peter J.; Atkinson, Kristen; Wragg, David Stephen; Colclasure, Andrew M. & Usseglio-Viretta, Francois L. E. [Vis alle 11 forfattere av denne artikkelen] (2023). Dynamic In-Plane Heterogeneous and Inverted Response of Graphite to Fast Charging and Discharging Conditions in Lithium-Ion Pouch Cells. Small science. ISSN 2688-4046. 3(7). doi: 10.1002/smsc.202200067.
• Paredes, Patricio; Rauwel, Erwan Yann; Wragg, David Stephen; Rapenne, Laetitia; Estephan, Elias & Volobujeva, Olga [Vis alle 7 forfattere av denne artikkelen] (2023). Sunlight-Driven Photocatalytic Degradation of Methylene Blue with Facile One-Step Synthesized Cu-Cu<inf>2</inf>O-Cu<inf>3</inf>N Nanoparticle Mixtures. Nanomaterials. ISSN 2079-4991. 13(8). doi: 10.3390/nano13081311. Fulltekst i vitenarkiv
• Kumar, Rohit; Rauwel, Protima; Kriipsalu, Mait; Wragg, David Stephen & Rauwel, Erwan (2023). Nanocobalt based (Co@Co(OH)2) sand nanocomposite applied to manganese extraction from contaminated water. Journal of Environmental Chemical Engineering. ISSN 2213-3437. 11(3). doi: 10.1016/j.jece.2023.109818. Fulltekst i vitenarkiv
• Capel Berdiell, Izar; Braghin, Giorgio Bruno; Cordero-Lanzac, Tomas; Beato, Pablo; Lundegaard, Lars F. & Wragg, David Stephen [Vis alle 8 forfattere av denne artikkelen] (2023). Tracking Structural Deactivation of H-Ferrierite Zeolite Catalyst During MTH with XRD. Topics in catalysis. ISSN 1022-5528. 66, s. 1418–1426. doi: 10.1007/s11244-023-01780-0. Fulltekst i vitenarkiv
• Strandbakke, Ragnar; Wragg, David Stephen; Sørby, Magnus Helgerud; Guzik, Matylda; Gunnæs, Anette Eleonora & Szpunar, Iga [Vis alle 12 forfattere av denne artikkelen] (2022). Structural properties of mixed conductor Ba1−xGd1−yLax+yCo2O6−δ. Dalton Transactions. ISSN 1477-9226. 51(48), s. 18667–18677. doi: 10.1039/d2dt02277j. Fulltekst i vitenarkiv Vis sammendrag

  Ba1−xGd1−yLax+yCo2O6−δ (BGLC) compositions with large compositional ranges of Ba, Gd, and La have been characterised with respect to phase compositions, structure, and thermal and chemical expansion. The results show a system with large compositional flexibility, enabling tuning of functional properties and thermal and chemical expansion. We show anisotropic chemical expansion and detailed refinements of emerging phases as La is substituted for Ba and Gd. The dominating phase is the double perovskite structure Pmmm, which is A-site ordered along the c-axes and with O vacancy ordering along the b-axis in the Ln-layer. Phases emerging when substituting La for Ba are orthorhombic Ba-deficient Pbnm and cubic LaCoO3-based R[3 with combining macron]c. When La is almost completely substituted for Gd, the material can be stabilised in Pmmm, or cubic Pm[3 with combining macron]m, depending on thermal and atmospheric history. We list thermal expansion coefficients for x = 0–0.3, y = 0.2.

• Sottmann, Jonas; Ruud, Amund; Fjellvåg, Øystein; Vaughan, Gavin B. M.; Di Michel, Marco & Fjellvåg, Helmer [Vis alle 9 forfattere av denne artikkelen] (2022). 5D total scattering computed tomography reveals the full reaction mechanism of a bismuth vanadate lithium ion battery anode. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 24(44), s. 27075–27085. doi: 10.1039/d2cp03892g. Fulltekst i vitenarkiv
• Kalantzopoulos, Georgios; Rojo Gama, Daniel; Pappas, Dimitrios; Dovgaliuk, Iurii; Olsbye, Unni & Beato, Pablo [Vis alle 9 forfattere av denne artikkelen] (2022). Real-time regeneration of a working zeolite monitored via operando X-ray diffraction and crystallographic imaging: how coke flees the MFI framework. Dalton Transactions. ISSN 1477-9226. 51(44), s. 16845–16851. doi: 10.1039/d2dt02845j. Fulltekst i vitenarkiv
• Nagpal, Keshav; Rapenne, Laetitia; Wragg, David Stephen; Rauwel, Erwan Yann & Rauwel, Protima (2022). The role of CNT in surface defect passivation and UV emission intensification of ZnO nanoparticles. Nanomaterials and Nanotechnology (NMNT). ISSN 1847-9804. 12. doi: 10.1177/18479804221079419.
• Fjellvåg, Asbjørn Slagtern; Jørgensen, Peter Stanley; Waller, David; Wragg, David Stephen; Michiel, Marco Di & Sjåstad, Anja Olafsen (2022). Mechanism of grain reconstruction of Pd and Pd/Ni wires during Pt–catchment. Materialia. ISSN 2589-1529. 21. doi: 10.1016/j.mtla.2022.101359. Fulltekst i vitenarkiv
• Hylland, Knut Tormodssønn; Schmidtke, Inga; Wragg, David Stephen; Nova, Ainara & Tilset, Mats (2022). Synthesis of substituted (N,C) and (N,C,C) Au(iii) complexes: the influence of sterics and electronics on cyclometalation reactions. Dalton Transactions. ISSN 1477-9226. 51(13), s. 5082–5097. doi: 10.1039/d2dt00371f. Fulltekst i vitenarkiv
• Brennhagen, Anders; Cavallo, Carmen; Wragg, David Stephen; Ponniah, Vajeeston; Sjåstad, Anja Olafsen & Koposov, Alexey [Vis alle 7 forfattere av denne artikkelen] (2022). Operando XRD studies on Bi2MoO6 as anode material for Na-ion batteries. Nanotechnology. ISSN 0957-4484. 33(18). doi: 10.1088/1361-6528/ac4eb5. Fulltekst i vitenarkiv Vis sammendrag

  Based on the same rocking-chair principle as rechargeable Li-ion batteries, Na-ion batteries are promising solutions for energy storage benefiting from low-cost materials comprised of abundant elements. However, despite the mechanistic similarities, Na-ion batteries require a different set of active materials than Li-ion batteries. Bismuth molybdate (Bi2MoO6) is a promising NIB anode material operating through a combined conversion/alloying mechanism. We report an operando x-ray diffraction (XRD) investigation of Bi2MoO6-based anodes over 34 (de)sodiation cycles revealing both basic operating mechanisms and potential pathways for capacity degradation. Irreversible conversion of Bi2MoO6 to Bi nanoparticles occurs through the first sodiation, allowing Bi to reversibly alloy with Na forming the cubic Na3Bi phase. Preliminary electrochemical evaluation in half-cells versus Na metal demonstrated specific capacities for Bi2MoO6 to be close to 300 mAh g−1 during the initial 10 cycles, followed by a rapid capacity decay. Operando XRD characterisation revealed that the increased irreversibility of the sodiation reactions and the formation of hexagonal Na3Bi are the main causes of the capacity loss. This is initiated by an increase in crystallite sizes of the Bi particles accompanied by structural changes in the electronically insulating Na–Mo–O matrix leading to poor conductivity in the electrode. The poor electronic conductivity of the matrix deactivates the NaxBi particles and prevents the formation of the solid electrolyte interface layer as shown by post-mortem scanning electron microscopy studies.

• Berntsen, Linn Neerbye; Solvi, Thomas Nordbø; Sørnes, Kristian; Wragg, David Stephen & Sandtorv, Alexander Harald (2021). Cu-catalyzed C(sp2)-N-bond coupling of boronic acids and cyclic imides. Chemical Communications. ISSN 1359-7345. 57(89), s. 11851–11854. doi: 10.1039/d1cc04356k.
• Hylland, Knut Tormodssønn; Gerz, Isabelle; Wragg, David Stephen; Øien-Ødegaard, Sigurd & Tilset, Mats (2021). The Reactivity of Multidentate Schiff Base Ligands Derived from Bi- and Terphenyl Polyamines towards M(II) (M=Ni, Cu, Zn, Cd) and M(III) (M=Co, Y, Lu). European Journal of Inorganic Chemistry (EurJIC). ISSN 1434-1948. s. 1869–1889. doi: 10.1002/ejic.202100170. Fulltekst i vitenarkiv
• Gerz, Isabelle; Jannuzzi, Sergio Augusto Venturinelli; Hylland, Knut Tormodssønn; Negri, Chiara; Wragg, David Stephen & Øien-Ødegaard, Sigurd [Vis alle 10 forfattere av denne artikkelen] (2021). Structural Elucidation, Aggregation, and Dynamic Behaviour of N,N,N,N-Copper(I) Schiff Base Complexes in Solid and in Solution: A Combined NMR, X-ray Spectroscopic and Crystallographic Investigation. European Journal of Inorganic Chemistry (EurJIC). ISSN 1434-1948. doi: 10.1002/ejic.202100722. Fulltekst i vitenarkiv
• Wragg, David Stephen; Kalantzopoulos, Georgios; Pappas, Dimitrios; Pinilla Herrero, Irene; Rojo-Gama, Daniel & Redekop, Evgeniy [Vis alle 10 forfattere av denne artikkelen] (2021). Mapping the coke formation within a zeolite catalyst extrudate in space and time by operando computed X-ray diffraction tomography. Journal of Catalysis. ISSN 0021-9517. 104, s. 1–6. doi: 10.1016/j.jcat.2021.07.001. Fulltekst i vitenarkiv
• Bernal, Fabian Leonardo Martinez; Lundvall, Fredrik; Kumar, Susmit; Hansen, Per-Anders S.; Wragg, David S. & Fjellvåg, Helmer [Vis alle 7 forfattere av denne artikkelen] (2021). Jahn-Teller active fluoroperovskites ACrF3 (A=Na+, K+): Magnetic and thermo-optical properties. PHYSICAL REVIEW MATERIALS. ISSN 2475-9953. 5(6). doi: 10.1103/PhysRevMaterials.5.064420. Fulltekst i vitenarkiv Vis sammendrag

  Chromium (II) fluoroperovskites A CrF 3 ( A = Na + , K + ) are strongly correlated Jahn-Teller active materials at low temperatures. In this paper, we examine the role that the A -site ion plays in this family of fluoroperovskites using both experimental methods (x-ray diffraction, optical absorption spectroscopy, and magnetic fields) and density functional theory simulations. Temperature-dependent optical absorption experiments show that the spin-allowed transitions E 2 and E 3 only merge completely for A = Na at 2 K. Field-dependent optical absorption measurements at 2 K show that the oscillating strength of the spin-allowed transitions in NaCrF 3 increases with increasing applied field. Direct magneto-optical correlations suppress the spin-flip transitions for KCrF 3 below its Néel temperature. In NaCrF 3 the spin-flip transitions vanish abruptly below 9 K revealing magneto-optical correlations possibly linked to crystal structure changes. This suggests that as the long range ordering is reduced, local Jahn-Teller effects in the individual CrF 4 − 6 octahedra take control of the observed behavior. Our results show clear deviation from the pattern found for the isoelectronic A x MnF 3 + x system. The size of the A -site cation is shown to be central in dictating the physical properties and phase transitions in A CrF 3 , opening up the possibility of varying the composition to create novel states of matter with tunable properties.

• Brennhagen, Anders; Cavallo, Carmen; Wragg, David; Sottmann, Jonas; Koposov, Alexey & Fjellvåg, Helmer (2021). Understanding the (De)Sodiation Mechanisms in Na‐Based Batteries through Operando X‐Ray Methods. Batteries & Supercaps. ISSN 2566-6223. 4(7), s. 1039–1063. doi: 10.1002/batt.202000294. Fulltekst i vitenarkiv Vis sammendrag

  Progress in the field of Na‐based batteries strongly relies on the development of new advanced materials. However, one of the main challenges of implementing new electrode materials is the understanding of their mechanisms (sodiation/desodiation) during electrochemical cycling. Operando studies provide extremely valuable insights into structural and chemical changes within different battery components during battery operation. The present review offers a critical summary of the operando X‐ray based characterization techniques used to examine the structural and chemical transformations of the active materials in Na‐ion, Na‐air and Na‐sulfur batteries during (de)sodiation. These methods provide structural and electronic information through diffraction, scattering, absorption and imaging or through a combination of these X‐ray‐based techniques. Challenges associated with cell design and data processing are also addressed herein. In addition, the present review provides a perspective on the future opportunities for these powerful techniques.

• Levchenko, Vladimir; Øien-Ødegaard, Sigurd; Wragg, David & Tilset, Mats (2020). Crystal structure of (N^C) cyclo-metalated Au III diazide at 100 K. Acta Crystallographica Section E: Crystallographic Communications. ISSN 2056-9890. 76, s. 1725–1727. doi: 10.1107/S2056989020012955.
• Agote-Arán, Miren; Kroner, Anna B.; Wragg, David; Slawinski, Wojciech Andrzej; Briceno, Martha & Islam, Husn U. [Vis alle 12 forfattere av denne artikkelen] (2020). Understanding the Deactivation Phenomena of Small-Pore Mo/H-SSZ-13 during Methane Dehydroaromatisation. Molecules. ISSN 1431-5157. 25(21), s. 1–15. doi: 10.3390/molecules25215048. Fulltekst i vitenarkiv
• Finegan, Donal; Quinn, Alexander; Wragg, David; Andrew, Colclasure; Xueken, Lu & Tan, Chun [Vis alle 17 forfattere av denne artikkelen] (2020). Spatial dynamics of lithiation and lithium plating during high-rate operation of graphite electrodes. Energy & Environmental Science. ISSN 1754-5692. 13, s. 2570–2584. doi: 10.1039/d0ee01191f. Fulltekst i vitenarkiv Vis sammendrag

  The principal inhibitor of fast charging lithium ion cells is the graphite negative electrode, where favorable conditions for lithium plating occur at high charge rates, causing accelerated degradation and safety concerns. The local response of graphite, both at the electrode and particle level, when exposed to fast charging conditions of around 6C is not well understood. Consequently, the conditions that lead to the onset of lithium plating, as well as the local dynamics of lithium plating and stripping, have also remained elusive. Here, we use high-speed (100 Hz) pencil-beam X-ray diffraction to repeatedly raster along the depth of a 101 μm thick graphite electrode in 3 μm steps during fast (up to 6C) charge and discharge conditions. Consecutive depth profiles from separator to current collector were each captured in 0.5 seconds, giving an unprecedented spatial and temporal description of the state of the electrode and graphite's staging dynamics during high rate conditions. The electrode is preferentially activated near the separator, and the non-uniformity increases with rate and is influenced by free-energy barriers between graphite's lithiation stages. The onset of lithium plating and stripping was quantified, occurring only within the first 15 μm from the separator. The presence of lithium plating changed the behavior of the underlying graphite, such as causing co-existence of LiC6 and graphite in the fully discharged state. Finally, the staging behavior of graphite at different rates was quantified, revealing a high dependency on rate and drastic hysteresis between lithiation and delithiation.

• Bernal, Fabian Leonardo Martinez; Gonano, Bruno Raymond Gino; Lundvall, Fredrik; Wragg, David; Fjellvåg, Helmer & Veillon, Fabien [Vis alle 8 forfattere av denne artikkelen] (2020). Canted antiferromagnetism in high-purity NaFeF3 prepared by a novel wet-chemical synthesis method. PHYSICAL REVIEW MATERIALS. ISSN 2475-9953. 4(11). doi: 10.1103/PhysRevMaterials.4.114412. Fulltekst i vitenarkiv
• Arstad, Bjørnar; Blom, Richard; Håkonsen, Silje Fosse; Pierchala, Joanna; Cobden, Paul & Lundvall, Fredrik [Vis alle 10 forfattere av denne artikkelen] (2020). Synthesis and Evaluation of K-Promoted Co3-xMgxAl-Oxides as Solid CO2 Sorbents in the Sorption-Enhanced Water−Gas Shift (SEWGS) Reaction. Industrial & Engineering Chemistry Research. ISSN 0888-5885. 59(40), s. 17837–17844. doi: 10.1021/acs.iecr.0c02322. Fulltekst i vitenarkiv Vis sammendrag

  Hydrogen is essential in a variety of large-scale chemical processes. As a carbon-free energy carrier, hydrogen has a potential for wide use within power production and transportation. However, most of the recent production methods involve the release of CO2 as a by-product. Hence, decarbonization of hydrogen production is one step to reduce CO2 emission into the Earth’s atmosphere. Several process schemes have been suggested for low-carbon emission production of hydrogen. In this work, we show how to improve solid sorbents for the sorption-enhanced water–gas shift (SEWGS) process, which is a process that exploits a solid sorbent in the water–gas shift reactor to capture CO2 in situ and drive the process toward an improved hydrogen yield. We report herein a series of CoxMg3-xAl materials based on hydrotalcites, promoted with various loadings of K. The materials have been characterized by BET, XRD, and NMR and tested for their CO2 adsorption performance in three adsorption–desorption cycles in a lab-scale fixed-bed reactor (20–22 bar, CO2 + steam as reactant gas, and isothermal conditions at 375 and 400 °C). The most promising material was subjected to a long-term test (120 adsorption–desorption cycles at similar conditions). This test indicates that a K-promoted Co1.5Mg1.5Al (22 wt % of added K2CO2 to the oxide) material has a higher cyclic capacity for CO2 than standard reference cases. We have estimated that the volumetric capacity (in mol/L unit) of this sorbent will be 23–26% higher than a standard reference material at 400 °C and 30–39% higher at 375 °C. This would, in fixed-bed columns, lead to significant reduction in the needed column volumes in the final process and reduce costs.

• Berntsen, Linn Neerbye; Nova, Ainara; Wragg, David & Sandtorv, Alexander Harald (2020). Cu-catalyzed N-3-Arylation of Hydantoins Using Diaryliodonium Salts. Organic Letters. ISSN 1523-7060. 22(7), s. 2687–2691. doi: 10.1021/acs.orglett.0c00642. Fulltekst i vitenarkiv Vis sammendrag

  A general Cu-catalyzed, regioselective method for the N-3-arylation of hydantoins is described. The protocol utilizes aryl(trimethoxyphenyl)iodonium tosylate as the arylating agent in the presence of triethylamine and a catalytic amount of a simple Cu-salt. The method is compatible with structurally diverse hydantoins and operates well with neutral aryl groups or aryl groups bearing weakly donating/withdrawing elements. It is also applicable for the rapid diversification of pharmaceutically relevant hydantoins.

• Li, Xinyu; Bianchini, Federico; Wind, Julia; Pettersen, Christine; Vajeeston, Ponniah & Wragg, David [Vis alle 7 forfattere av denne artikkelen] (2020). Insights into Crystal Structure and Diffusion of Biphasic Na2Zn2TeO6. ACS Applied Materials & Interfaces. ISSN 1944-8244. 12(25), s. 28188–28198. doi: 10.1021/acsami.0c05863. Fulltekst i vitenarkiv
• Bernal, Fabian Leonardo Martinez; Sottmann, Jonas; Wragg, David; Fjellvåg, Helmer; Fjellvåg, Øystein & Drathen, Christina [Vis alle 8 forfattere av denne artikkelen] (2020). Structural and magnetic characterization of the elusive Jahn-Teller active NaCrF3. PHYSICAL REVIEW MATERIALS. ISSN 2475-9953. 4(5). doi: 10.1103/PhysRevMaterials.4.054412. Fulltekst i vitenarkiv
• Kalantzopoulos, Georgios N.; Lundvall, Fredrik; Thorshaug, Knut; Lind, Anna Maria; Vajeeston, Ponniah & Dovgaliuk, Iurii [Vis alle 9 forfattere av denne artikkelen] (2020). Factors Determining Microporous Material Stability in Water: The Curious Case of SAPO-37. Chemistry of Materials. ISSN 0897-4756. 32(4), s. 1495–1505. doi: 10.1021/acs.chemmater.9b04510. Fulltekst i vitenarkiv
• Li, Xinyu; Bianchini, Federico; Wind, Julia; Vajeeston, Ponniah; Wragg, David & Fjellvåg, Helmer (2019). P2 Type Layered Solid-State Electrolyte Na2Zn2TeO6: Crystal Structure and Stacking Faults . Journal of the Electrochemical Society. ISSN 0013-4651. 166(15), s. A3830–A3837. doi: 10.1149/2.1231915jes.
• Agote-Aran, Miren; Kroner, Anna B; Islam, Husn U; Slawinski, Wojciech Andrzej; Wragg, David & Lezcano-González, Inés [Vis alle 7 forfattere av denne artikkelen] (2019). Determination of Molybdenum Species Evolution during Non‐Oxidative Dehydroaromatization of Methane and its Implications for Catalytic Performance. ChemCatChem. ISSN 1867-3880. 11(1), s. 473–480. doi: 10.1002/cctc.201801299. Fulltekst i vitenarkiv
• Lundvall, Fredrik; Kalantzopoulos, Georgios N.; Wragg, David; Arstad, Bjørnar; Blom, Richard & Sjåstad, Anja Olafsen [Vis alle 7 forfattere av denne artikkelen] (2019). Characterization and evaluation of synthetic Dawsonites as CO2 sorbents. Fuel. ISSN 0016-2361. 236, s. 747–754. doi: 10.1016/j.fuel.2018.09.057. Fulltekst i vitenarkiv
• Holmsen, Marte Sofie; Nova, Ainara; Hylland, Knut Tormodssønn; Wragg, David; Øien-Ødegaard, Sigurd & Heyn, Richard H. [Vis alle 7 forfattere av denne artikkelen] (2018). Synthesis of a (N,C,C) Au(III) pincer complex via Csp3–H bond activation: increasing catalyst robustness by rational catalyst design. Chemical Communications. ISSN 1359-7345. 54(79), s. 11104–11107. doi: 10.1039/c8cc05489d.
• Grajeda, Javier; Nova, Ainara; Balcells, David; Bruch, Quinton J.; Wragg, David & Heyn, Richard H. [Vis alle 8 forfattere av denne artikkelen] (2018). Synthesis and characterization of stable gold(III) PNP pincer complexes. European Journal of Inorganic Chemistry (EurJIC). ISSN 1434-1948. 2018(26), s. 3113–3117. doi: 10.1002/ejic.201800019.
• Kalantzopoulos, Georgios N.; Lundvall, Fredrik; Checchia, Stefano; Lind, Anna Maria; Wragg, David & Fjellvåg, Helmer [Vis alle 7 forfattere av denne artikkelen] (2018). In Situ Flow MAS NMR Spectroscopy and Synchrotron PDF Analyses of the Local Response of the Brønsted Acidic Site in SAPO-34 during Hydration at Elevated Temperatures. ChemPhysChem. ISSN 1439-4235. 19(4), s. 519–528. doi: 10.1002/cphc.201700973.
• Rojo-Gama, Daniel; Mentel, Lukasz; Kalantzopoulos, Georgios N.; Pappas, Dimitrios; Dovgaliuk, Iurii & Olsbye, Unni [Vis alle 11 forfattere av denne artikkelen] (2018). Deactivation of Zeolite Catalyst H-ZSM-5 during Conversion of Methanol to Gasoline: Operando Time- and Space-Resolved X-ray Diffraction. The Journal of Physical Chemistry Letters. ISSN 1948-7185. 9(6), s. 1324–1328. doi: 10.1021/acs.jpclett.8b00094. Fulltekst i vitenarkiv
• Rauwel, Erwan Yann; Simón-Gracia, Lorena; Guha, Mithu; Rauwel, Protima; Küünal, Siim & Wragg, David (2017). Silver metal nanoparticles study for biomedical and green house applications. IOP Conference Series: Materials Science and Engineering. ISSN 1757-8981. 175:012011(1), s. 1–6. doi: 10.1088/1757-899X/175/1/012011.
• Øien-Ødegaard, Sigurd; Shearer, Greig Charles; Wragg, David & Lillerud, Karl Petter (2017). Pitfalls in metal-organic framework crystallography: Towards more accurate crystal structures. Chemical Society Reviews. ISSN 0306-0012. 46(16), s. 4867–4876. doi: 10.1039/c6cs00533k.
• Sottmann, Jonas; Di Michiel, Marco; Fjellvåg, Helmer; Malavasi, Lorenzo; Margadonna, Serena & Vajeeston, Ponniah [Vis alle 8 forfattere av denne artikkelen] (2017). Chemical Structures of Specific Sodium Ion Battery Components Determined by Operando Pair Distribution Function and X-ray Diffraction Computed Tomography. Angewandte Chemie International Edition. ISSN 1433-7851. 56(38), s. 11385–11389. doi: 10.1002/anie.201704271. Fulltekst i vitenarkiv
• Morris, Samuel A; Bignami, Giulia P M; Tian, Yuyang; Navarro, Marta; Firth, Daniel S & Cejka, Jiri [Vis alle 12 forfattere av denne artikkelen] (2017). In situ solid-state NMR and XRD studies of the ADOR process and the unusual structure of zeolite IPC-6. Nature Chemistry. ISSN 1755-4330. 9(10), s. 1012–1018. doi: 10.1038/nchem.2761.
• Kalyva, Maria Evangelou; Wragg, David; Fjellvåg, Helmer & Sjåstad, Anja Olafsen (2017). Engineering Functions into Platinum and Platinum?Rhodium Nanoparticles in a One-Step Microwave Irradiation Synthesis. ChemistryOpen. ISSN 2191-1363. 6(2), s. 273–281. doi: 10.1002/open.201600163.
• Rojo-Gama, Daniel; Nielsen, Malte; Wragg, David; Dyballa, Michael Martin; Holzinger, Julian & Falsig, Hanne [Vis alle 12 forfattere av denne artikkelen] (2017). A Straightforward Descriptor for the Deactivation of Zeolite Catalyst H-ZSM-5. ACS Catalysis. ISSN 2155-5435. 7(12), s. 8235–8246. doi: 10.1021/acscatal.7b02193. Fulltekst i vitenarkiv
• Lundvall, Fredrik; Wragg, David; Vajeeston, Ponniah; Dietzel, Pascal D.C. & Fjellvåg, Helmer (2017). Ab initio structure solution and thermal stability evaluation of a new Ca(II) 3D coordination polymer using synchrotron powder X-ray diffraction data. CrysteEngComm. ISSN 1466-8033. 19(39), s. 5857–5863. doi: 10.1039/c7ce01389b. Vis sammendrag

  A new coordination polymer was synthesized hydrothermally using 4,4′-dimethoxy-3,3′-biphenyldicarboxylic acid (H2dmbpdc) and Ca(NO3)2·4H2O. The structure of the new compound, Ca(dmbpdc)(H2O)2 (CPO-70-Ca), was determined from powder X-ray diffraction (PXRD) data using simulated annealing, followed by Rietveld refinement of the structure. The framework is based on one-dimensional metal carboxylate chains that are linked by the organic linker into a three-dimensional network with rhombic channels. The as-synthesized material resembles our recently reported compound CPO-69-Ca, and shares the same sra topology. The asymmetric unit comprises one calcium atom, one fully deprotonated linker, one water molecule coordinated to the metal cation as well as one solvent water molecule located in the rhombic channels. The metal cation is eight-coordinate, forming an irregular coordination polyhedron. The thermal behavior of CPO-70-Ca was investigated in an in situ structural analysis by variable temperature powder X-ray diffraction. This study revealed an interesting response to solvent removal from the as-synthesized structure. The results include a partially desolvated version of CPO-70-Ca and a structural transformation to CPO-69-Ca upon full desolvation.

• Lundvall, Fredrik; Kalantzopoulos, Georgios N.; Wragg, David; Arstad, Bjørnar; Blom, Richard & Sjåstad, Anja Olafsen [Vis alle 7 forfattere av denne artikkelen] (2017). Thermogravimetric Analysis – A Viable Method for Screening Novel Materials for the Sorbent Enhanced Water-gas Shift Process. Energy Procedia. ISSN 1876-6102. 114, s. 2294–2303. doi: 10.1016/j.egypro.2017.03.1372. Fulltekst i vitenarkiv Vis sammendrag

  Pre-combustion CO2 capture technologies are becoming viable alternatives to more conventional post-combustion capture by gas emissions scrubbing. The sorbent enhanced water-gas shift (SEWGS) process is a promising future technology for CO2 capture. However, the process needs better performing materials than those available today to be competitive against state-of-the-art scrubbing technologies. Layered double hydroxides (LDH) are a promising class of materials to improve the performance of the SEWGS process. These materials have a general formula of M2+1-xM3+x(OH)2(An-)x/n·mH2O, and can be tuned by substituting the metal species, changing the M2+/M3+ ratio, adjusting the synthesis parameters to influence morphology or by adding so-called promotors to improve performance. To aid an ongoing systematic study looking at several of these parameters we have developed a simple yet efficient way of screening materials for further in-depth studies. The method is highly suitable for a typical laboratory setting, and is based on thermogravimetric analysis combined with cyclic exposure to selected gases. In this article we present the results of applying the method to a selection of benchmark materials.

• Sottmann, Jonas; Herrmann, Matthias; Vajeeston, Ponniah; Ruud, Amund; Drathen, Christina & Emerich, Hermann [Vis alle 8 forfattere av denne artikkelen] (2017). Bismuth Vanadate and Molybdate: Stable Alloying Anodes for Sodium-Ion Batteries. Chemistry of Materials. ISSN 0897-4756. 29(7), s. 2803–2810. doi: 10.1021/acs.chemmater.6b04699.
• Kalantzopoulos, Georgios N.; Lundvall, Fredrik; Lind, Anna Maria; Arstad, Bjørnar; Chernyshov, Dmitry & Fjellvåg, Helmer [Vis alle 7 forfattere av denne artikkelen] (2017). SAPO-37 microporous catalysts: revealing the structural transformations during template removal. Catalysis, Structure & Reactivity. ISSN 2055-0758. 3(1-2), s. 79–88. doi: 10.1080/2055074X.2016.1262569. Fulltekst i vitenarkiv Vis sammendrag

  We have studied the structural behavior of SAPO-37 during calcination using simultaneous in situ powder X-ray diffraction (PXRD) and mass spectroscopy (MS) in addition to ex situ thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). A spike in the unit cell volume corresponding to template removal (tracked using the occupancy of the crystallographic sites in the SAPO-37 cages) is revealed from the XRD data and is strongly correlated with the DSC curve. The occupancy of the different template molecules in the faujasite (FAU) and sodalite (SOD) cages is strongly related to the two mass loss steps observed in the TGA data. The templates act as a physical stabilizing agent, not allowing any substantial unit cell response to temperature changes until they are removed. The FAU cages and SOD cages have different thermal response to the combustion of each template. The FAU cages are mainly responsible for the unit cell volume expansion observed after the template combustion. This expansion seems to be related with residual coke from template combustion. We could differentiate between the thermal response of oxygen and T-atoms. The T–O–T angle between two double 6-rings and a neighboring T–O–T linkage shared by SOD and FAU had different response to the thermal events. We were able to monitor the changes in the positions of oxygen and T-atoms during the removal of TPA+ and TMA+. Large changes to the framework structure at the point of template removal may have a significant effect on the long-term stability of the material in its activated form.

• Gorbitz, Carl Henrik; Wragg, David; Bakke, Ingrid Marie Bergh; Fleicher, Christian; Grønnevik, Gaute & Mykland, Maria [Vis alle 10 forfattere av denne artikkelen] (2016). A phase transition from monoclinic C2 with Z' = 1 to triclinic P1 with Z' = 4 for the quasiracemate L-2-aminobutyric acid–D-methionine (1/1). Acta Crystallographica Section C: Crystal Structure Communications. ISSN 0108-2701. 72, s. 536–543. doi: 10.1107/S2053229616008858.
• Sottmann, Jonas; Homs-Regojo, Roberto; Wragg, David; Fjellvåg, Helmer; Margadonna, Serena & Emerich, Hermann (2016). Versatile electrochemical cell for Li/Na-ion batteries and high-throughput setup for combined operando X-ray diffraction and absorption spectroscopy. Journal of Applied Crystallography. ISSN 0021-8898. 49(6), s. 1972–1981. doi: 10.1107/S160057671601428X.

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• Wragg, David Stephen; Wachs, Israel E.; Bañares, Miguel A. & Svelle, Stian (2023). Springer Handbook of Advanced Catalyst Characterization. Springer. ISBN 978-3-031-07125-6. 5(1). 1117 s.

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• Brennhagen, Anders; Skurtveit, Amalie; Skautvedt, Casper; Cavallo, Carmen; Wragg, David Stephen & Vajeeston, Ponniah [Vis alle 9 forfattere av denne artikkelen] (2024). Revealing the (de)sodiation mechanisms of Bi-metallates through operando X-ray characterisation. Vis sammendrag

  Na-ion batteries is entering the battery market as an alternative to Li-ion batteries. To improve their overall performance it is crucial to develop new types of anode materials with high capacity and long cycle life. Materials combing conversion and alloying mechanisms (CAMs) are promising anodes with their high capacity, but obtaining good cycling stability is still challenging. A comprehensive understanding of the cycling and degradation mechanism of these materials is crucial to improve their performance. Bi-metallates, with a general formula of Bi−TM−O (TM = transition metal) is a group of ternary CAMs. Their general cycling mechanism consists of an irreversible conversion reaction forming nanoparticles of Bi-metal embedded in a Na-TM-O matrix during the first sodiation, followed by a reversible two-step alloying reaction forming Na3Bi with NaBi as an intermediate phase. In this work, we have used operando X-ray diffraction (XRD), pair distribution function (PDF) analysis and X-ray absorption spectroscopy (XAS) to investigate the desodiation mechanisms of Bi2MoO6 and BiFeO3. Through this work, we discovered that Bi2MoO6 forms the cubic version of Na3Bi (c-Na3Bi) while BiFeO3 forms hexagonal Na3Bi (h-Na3Bi) in addition to c-Na3Bi during the first sodiation. In the desodiated state, the Bi-particles are partially oxidised, while still maintaining the Bi-metal structure, indicating that it is only the Bi atoms at the interface between the Bi nanoparticles and the Na−TM−O matrix that is oxidised. During cycling the NaxBi particles grow larger thus increasing the distance between them and increasing the impedance in the material. This is considered to be the main driver for the capacity degradation that was observed during the first 20 cycles. The operando XAS data also revealed that Mo6+ in Bi2MoO6 does not change oxidation state during cycling, but changes coordination between tetrahedral and distorted octahedral coordination during cycling. The cycling and degradation mechanisms of Bi2MoO6 is summarised in Figure 1.

• Svelle, Stian; Lundegaard, Lars Fahl; Beato, Pablo & Wragg, David Stephen (2023). Case Studies: Crystallography as a Tool for Studying Methanol Conversion in Zeolites, Springer Handbook of Advanced Catalyst Characterization. Springer. ISSN 978-3-031-07125-6. s. 541–563. doi: 10.1007/978-3-031-07125-6_26.
• Capel Berdiell, Izar; Wragg, David Stephen; Beato, Pablo; Lundegaard, Lars Fahl; Di Michel, Marco & Svelle, Stian (2023). Temperature Programmed Oxidation Probed with X-ray Diffraction Computed Tomography.
• Svelle, Stian; Capel Berdiell, Izar; Wragg, David Stephen; Beato, Pablo & Lundegaard, Lars Fahl (2023). In situ and operando X-ray diffraction as a tool to monitor zeolite catalyst deactivation .
• Wragg, David Stephen (2023). Cleaning Up Operando Battery X-Ray Diffraction With Total Scattering Computed Tomography.
• Skurtveit, Amalie; Pastusic, Andrew; Brennhagen, Anders; Cavallo, Carmen; Wragg, David Stephen & Koposov, Alexey (2023). High-Rate Performance of Antimony Chalcogenides (Sb2X3) Studied by Operando X-ray Diffraction (XRD).
• Brennhagen, Anders; Skautvedt, Casper; Cavallo, Carmen; Skurtveit, Amalie; Wragg, David Stephen & Koposov, Alexey [Vis alle 9 forfattere av denne artikkelen] (2023). Revealing the Cycling and Degradation Mechanism of Bi-Metallates as Anode Materials fro Na-ion Batteries. Vis sammendrag

  Na-ion batteries (NIBs) represent an emerging alternative to modern Li-ion batteries. To improve the overall performance of NIBs it is crucial to develop new types of anode materials with high capacity and long cycle life. Among the anode candidates, materials operating under combined conversion and alloying mechanisms (CAMs) are considered as promising. They are capable of delivering high capacity, however, despite theoretical predictions the cycling stability is still below expectations. Therefore, a comprehensive understanding of the cycling and degradation mechanisms of CAMs is crucial to improve their performance. However, these materials undergo multiple chemical transformations, which often involves formation of amorphous and nanocrystalline phases during cycling. Such chemical complexity substantially impedes their full characterization and understanding. Bismuth metallates, with a general formula of Bi-TM-O (TM = transition metal), is a group of ternary CAMs. Their general cycling mechanism consists of an irreversible conversion reaction, which leads to formation of Bi nanoparticles embedded in a Na-TM-O matrix during the first sodiation. This is followed by a reversible two-step alloying reaction leading to formation of Na3Bi with NaBi as an intermediate phase. In this work, we have used operando X-ray diffraction over the course of ∼30 cycles to study the cycling and degradation mechanisms of two CAMs - Bi2MoO6 and BiFeO3. With the help of ex situ X-ray absorption spectroscopy and pair distribution function (PDF) analysis, we have revealed new insights into these materials in addition to confirming the general cycling mechanism. Both materials form the cubic phase of Na3Bi (c-Na3Bi) in the sodiated state with some noticeable differences. While, the hexagonal Na3Bi (h-Na3Bi) phase starts to form after 10 cycles in Bi2MoO6, a combination of c-Na3Bi and h-Na3Bi can be observed after the first cycle in BiFeO3. The formation of c-Na3Bi is kinetically favorable in these systems, while h-Na3Bi is the more thermodynamically stable and, therefore, forms later in the cycling process. Both materials shows three distinct regions of capacity degradation, where the first is initiated by a growth in the crystallite sizes of Bi-particles. This is followed by a disappearance of the Bi-phase as the second step. The last degradation phase is related to the disappearance of the NaBi-phase and locking the system in the sodiated state. The present talk will discuss the mechanisms of these degradation steps in view of the future development of CAMs in greater details.

• Sottmann, Jonas; Ruud, Amund; Fjellvåg, Øystein Slagtern; Vaughan, Gavin B. M.; Di Michel, Marco & Fjellvåg, Helmer [Vis alle 9 forfattere av denne artikkelen] (2023). Erratum: 5D total scattering computed tomography reveals the full reaction mechanism of a bismuth vanadate lithium ion battery anode (Phys. Chem. Chem. Phys. (2022) 24 (27075-27085) DOI: 10.1039/D2CP03892G). Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. doi: 10.1039/d3cp90076b.
• Brennhagen, Anders; Cavallo, Carmen; Wragg, David Stephen; Koposov, Alexey; Ponniah, Vajeeston & Sjåstad, Anja Olafsen [Vis alle 7 forfattere av denne artikkelen] (2023). Tracing the (De)sodiation of Bi2MoO6 Through Good and Bad Times With Operando XRD. Vis sammendrag

  Na-ion batteries (NIBs) generally have slightly lower energy densities than Li-ion batteries (LIBs), but the abundancy of Na could make NIBs cheaper and more sustainable. The search for new anode materials is essential for further development of NIBs. Anode materials combining conversion and alloying mechanisms (CAMs) are promising because of their high capacity and high rate capabilities, but their complex cycling mechanisms involving amorphous phases are challenging to study [1]. Bi2MoO6 is an example of a CAM that has high initial capacity, but struggles with cycling stability and undergoes major changes during cycling. Detailed understanding of its cycling and degradation mechanism will hopefully enable us to improve the cycling stability of Bi2MoO6 and CAMs in general. Therefore, we have studied Bi2MoO6 using a combination of operando X-ray diffraction (Fig. 1), pair distribution function, X-ray absorption spectroscopy and transmission electron microscopy [3]. This revealed that during the first sodiation, an irreversible conversion of Bi2MoO6 occurs, creating Bi nanoparticles embedded in an amorphous Na-Mo-O matrix. The Bi particles then reversibly alloy with Na, forming cubic Na3Bi leading to a specific capacity close to 300 mAh g−1 for the 10 first cycles. During these cycles, we observe a growth in the crystallite size of the alloying particles, which is probably the leading cause of the rapid capacity decay after cycle 10 where the sodiation of Bi becomes irreversible leaving several inactive Na3Bi particles.

• Capel Berdiell, Izar; König, Nico; Junge, Nicolai Haaber; Kalantzopoulos, Georgios; Beato, Pablo & Svelle, Stian [Vis alle 8 forfattere av denne artikkelen] (2022). Tracking deactivation level of zeolite H-beta catalysts with novel XRD models.
• Capel Berdiell, Izar; Braghin, Giorgio Bruno; Cordero-Lanzac, Tomas; Beato, Pablo; Lundegaard, Lars Fahl & Wragg, David Stephen [Vis alle 8 forfattere av denne artikkelen] (2022). Tracking Structural Deactivation of H-Ferrierite Zeolite Catalyst during MTH with XRD.
• Skurtveit, Amalie; Cavallo, Carmen; Wragg, David Stephen & Koposov, Alexey (2022). Revealing the (de)sodiation mechanism of antimony chalcogenides Sb2X3 with operando XRD.
• Wragg, David Stephen (2022). Big Data in XRD: Processing a huge number of sub optimal datasets with TOPAS.
• Brennhagen, Anders; Cavallo, Carmen; Wragg, David Stephen; Koposov, Alexey; Ponniah, Vajeeston & Sjåstad, Anja Olafsen [Vis alle 7 forfattere av denne artikkelen] (2022). Tracing the (De)sodiation of Bi2MoO6 Through Good and Bad Times With Operando XRD. Vis sammendrag

  Anode materials combining conversion and alloying mechanisms (CAMs) are promising for Na-ion batteries, but their complex cycling mechanisms are challenging to study. Understanding the (de)sodiation mechanism is crucial and, in several cases, requires advanced synchrotron characterization. Operando synchrotron studies are generally limited to one or two sodiation cycles, which are not fully comprehensive for CAMs. Therefore, herein, we studied the sodiation and desodiation of Bi2MoO6-based anodes with laboratory-based operando X-ray diffraction exceeding more than 30 cycles to have a complete overview of our CAM’s mechanism. This revealed important aspects of the cycling and degradation mechanisms in the material. During the first sodiation, an irreversible conversion of Bi2MoO6 occurs, creating Bi nanoparticles embedded in an amorphous Na-Mo-O matrix. The Bi particles then reversibly alloy with Na forming cubic Na3Bi leading to a specific capacity close to 300 mAh g−1 for the 10 first cycles. This is followed by a rapid capacity decay where the sodiation of Bi becomes irreversible leaving several inactive Na3Bi particles. To the best of our knowledge, this is due to the observed crystal growth of the Bi particles accompanied by structural changes in the insulating Na-Mo-O leading to poor conductivity in the electrodes. The poor electronic conductivity of the matrix deactivates the NaxBi particles and prevents the formation of the solid electrolyte interface layer as shown by post-mortem scanning electron microscopy studies.

• Brennhagen, Anders; Cavallo, Carmen; Wragg, David Stephen; Ponniah, Vajeeston; Sjåstad, Anja Olafsen & Koposov, Alexey [Vis alle 7 forfattere av denne artikkelen] (2022). Corrigendum: Operando XRD studies on Bi2MoO6 as anode material for Na-ion batteries (Nanotechnology (2022)33 (185402) DOI: 10.1088/1361-6528/ac4eb5). Nanotechnology. ISSN 0957-4484. 33(35). doi: 10.1088/1361-6528/ac72b2.
• Brennhagen, Anders; Cavallo, Carmen; Wragg, David Stephen; Ponniah, Vajeeston; Sjåstad, Anja Olafsen & Koposov, Alexey [Vis alle 7 forfattere av denne artikkelen] (2022). Tracing the (de)sodiation of Bi2MoO6 through good and bad times with operando XRD. Vis sammendrag

  Anode materials combining conversion and alloying mechanisms (CAMs) are promising for Na-ion batteries, but their complex cycling mechanisms are challenging to study1. Understanding the (de)sodiation mechanism is crucial and, in several cases, requires advanced synchrotron characterization. Operando synchrotron studies are generally limited to one or two sodiation cycles, which are not fully comprehensive for CAMs2. Therefore, herein, we studied the sodiation and desodiation of Bi2MoO6-based anodes with laboratory-based operando X-ray diffraction exceeding more than 30 cycles to have a complete overview of our CAM’s mechanism (Figure 1)3. This revealed important aspects of the cycling and degradation mechanisms in the material. During the first sodiation, an irreversible conversion of Bi2MoO6 occurs, creating Bi nanoparticles embedded in an amorphous Na-Mo-O matrix. The Bi particles then reversibly alloy with Na forming cubic Na3Bi leading to a specific capacity close to 300 mAh g−1 for the 10 first cycles. This is followed by a rapid capacity decay where the sodiation of Bi becomes irreversible leaving several inactive Na3Bi particles. To the best of our knowledge, this is due to the observed crystal growth of the Bi particles accompanied by structural changes in the insulating Na-Mo-O leading to poor conductivity in the electrodes. The poor electronic conductivity of the matrix deactivates the NaxBi particles and prevents the formation of the solid electrolyte interface layer as shown by post-mortem scanning electron microscopy studies.

• Brennhagen, Anders; Cavallo, Carmen; Wragg, David Stephen; Koposov, Alexey; Ponniah, Vajeeston & Sjåstad, Anja Olafsen [Vis alle 7 forfattere av denne artikkelen] (2021). Operando XRD study on Bi2MoO6 as anode material for Na-ion batteries. Vis sammendrag

  Na-ion batteries (NIBs) could be a good alternative to Li-ion batteries (LIBs) due to the large abundance and availability of sodium resources. The search for good anode materials is one of the big challenges since graphite, which is the most common anode material for LIB, does not work well in NIBs. We are developing Bi2MoO6 as an anode material for NIBs, and will explain the main cycling mechanism. By utilizing a combination of conversion and alloying reactions, the material achieves high capacity while still maintaining a decent cycling stability. The complex cycling mechanism also makes it an interesting and challenging material to characterize during cycling. In this poster, we present high quality operando XRD data of the material during several cycles, acquired in the home lab. The data clearly shows that the reversible alloying reaction of Bi-metal to cubic Na3Bi gives the main capacity contribution, after the initial conversion reaction. This indicates formation of nanocrystalline Bi-particles, as nanocrystalline Bi-metal has shown the same reaction mechanism while microcrystalline Bi instead forms the hexagonal phase of Na3Bi. The molybdenum goes into an amorphous matrix that is only partially electrochemically active. The phases formed with molybdenum during cycling are difficult to characterize, due to their amorphous nature, and remain an unsolved mystery.

• Brennhagen, Anders; Cavallo, Carmen; Wragg, David Stephen; Sjåstad, Anja Olafsen; Ponniah, Vajeeston & Fjellvåg, Helmer (2021). Operando XRD studies on Bi2MoO6 as anode material for Na-ion batteries. Vis sammendrag

  Na-ion batteries (NIBs) could be a good alternative to Li-ion batteries (LIBs) due to the large abundance and availability of sodium resources. The search for good anode materials is one of the big challenges since graphite, which is the most common anode material for LIB, does not work well in NIBs. We are developing Bi2MoO6 as an anode material for NIBs, and will explain the main cycling mechanism. By utilizing a combination of conversion and alloying reactions, the material achieves high capacity while still maintaining a decent cycling stability. The complex cycling mechanism also makes it an interesting and challenging material to characterize during cycling. In this poster, we present high quality operando XRD data of the material during several cycles, acquired in the home lab. The data clearly shows that the reversible alloying reaction of Bi-metal to cubic Na3Bi gives the main capacity contribution, after the initial conversion reaction. This indicates formation of nanocrystalline Bi-particles, as nanocrystalline Bi-metal has shown the same reaction mechanism while microcrystalline Bi instead forms the hexagonal phase of Na3Bi. The molybdenum goes into an amorphous matrix that is only partially electrochemically active. The phases formed with molybdenum during cycling are difficult to characterize, due to their amorphous nature, and remain an unsolved mystery.

• Capellas Espuny, Montserrat; Wragg, David Stephen & Brennhagen, Anders (2021). From Oslo to Grenoble in the search of next generation batteries. [Internett]. esrf.fr.
• Brennhagen, Anders; Cavallo, Carmen; Wragg, David; Vajeeston, Ponniah; Sjåstad, Anja Olafsen & Fjellvåg, Helmer (2021). Bi4V2O11/RGO composite as conversion and alloying anode for Na-ion batteries.
• Brennhagen, Anders; Wragg, David; Fjellvåg, Helmer; Vajeeston, Ponniah; Sjåstad, Anja Olafsen & Cavallo, Carmen (2021). Beyond Insertion: Conversion alloying Bi/RGO-based materials as novel anodes for Na-ion batteries.
• Wragg, David (2020). Beamline Facilities for Chemistry and Materials Science.
• Wragg, David; Fjellvåg, Øystein; Fjellvåg, Helmer; Sottmann, Jonas; Vaughan, Gavin B M & Di Michel, Marco [Vis alle 7 forfattere av denne artikkelen] (2020). Operando Total Scattering Computed Tomography: Making the Invisible Visible .
• Cavallo, Carmen; Brennhagen, Anders; Wragg, David & Fjellvåg, Helmer (2020). Beyond Insertion: Conversion alloying Bi/RGO-based materials as anode for Na-ion batteries .
• Beale, Andrew M.; Lezcano-González, Inés; Slawinski, Wojciech Andrzej & Wragg, David Stephen (2019). Correction: Correlation between Cu ion migration behaviour and deNOx activity in Cu-SSZ-13 for the standard NH3-SCR reaction (Chemical Communications (2016) 52 (6170-6173) DOI: 10.1039/c6cc00513f). Chemical Communications. ISSN 1359-7345. 55(11), s. 1667–1667. doi: 10.1039/c9cc90036e.
• Wragg, David; Fjellvåg, Øystein; Ruud, Amund; Fjellvåg, Helmer; Vajeeston, Ponniah & Vaughan, Gavin B M [Vis alle 9 forfattere av denne artikkelen] (2019). XRD/PDF computed tomography and how to get the best possible operando data from ion batteries.
• Wragg, David (2019). Be prepared!How an Advanced Home Lab can Improve Our Synchrotron Science.
• Wragg, David; Ruud, Amund; Fjellvåg, Øystein; Fjellvåg, Helmer; lebedev, Oleg & Di Michel, Marco [Vis alle 9 forfattere av denne artikkelen] (2019). PDF Analysis of Batteries Using Diffraction Computed Tomography.
• Wragg, David; Ruud, Amund; Fjellvåg, Helmer; Fjellvåg, Øystein; Vajeeston, Ponniah & Sottmann, Jonas [Vis alle 9 forfattere av denne artikkelen] (2019). PDF Analysis of Batteries Using Diffraction Computed Tomography.
• Wragg, David; Sottmann, Jonas; Ruud, Amund; Fjellvåg, Øystein & Vaughan, Gavin B M (2018). Combined refinement of XRD and PDF data from nanomaterials.
• Wragg, David; Sottmann, Jonas; Ruud, Amund; Fjellvåg, Helmer; Fjellvåg, Øystein & Vajeeston, Ponniah [Vis alle 9 forfattere av denne artikkelen] (2018). Operando X-ray Diffraction Studies of Battery Materials.
• Wragg, David; Ruud, Amund; Sottmann, Jonas; Vajeeston, Ponniah; Fjellvåg, Helmer & Fjellvåg, Øystein [Vis alle 8 forfattere av denne artikkelen] (2018). New Anodes for Sodium and Lithium Ion Batteries.
• Strandbakke, Ragnar; Wragg, David; Carvalho, Patricia; Mielewczyk-Gryn, Aleksandra; Wachowski, Sebastian & Balaguer, Maria [Vis alle 8 forfattere av denne artikkelen] (2018). Coupled hydration and red-ox in MIEC BGLC perovskites .
• Kalantzopoulos, Georgios N.; Lundvall, Fredrik; Nyborg Broge, Nils Lau; Søndergaard-Pedersen, Frederik M; Lind, Anna Maria & Arstad, Bjørnar [Vis alle 9 forfattere av denne artikkelen] (2018). Real-Time Evolution of SAPO Catalysts' Local Coordination during Hydrothermal Treatment.
• Wragg, David; Sottmann, Jonas; Vajeeston, Ponniah & Ruud, Amund (2017). The intriguing mechanism of phosphorus anodes for sodium ion batteries Revealed by operando pair distribution function and X-ray diffraction computed tomography.
• Lundvall, Fredrik; Kalantzopoulos, Georgios N.; Wragg, David; Arstad, Bjørnar; Blom, Richard & Sjåstad, Anja Olafsen [Vis alle 7 forfattere av denne artikkelen] (2017). Dawsonite as sorbent for the SEWGS process.
• Kalantzopoulos, Georgios N.; Lundvall, Fredrik; Lind, Anna Maria; Arstad, Bjørnar; Wragg, David & Fjellvåg, Helmer (2017). Sub-unit cell structural transformations during template-removal and hydration of SAPO-37 microporous catalysts.
• Lundvall, Fredrik; Kalantzopoulos, Georgios N.; Wragg, David; Arstad, Bjørnar; Blom, Richard & Sjåstad, Anja Olafsen [Vis alle 7 forfattere av denne artikkelen] (2017). Finding new materials for the SEWGS process.
• Lundvall, Fredrik; Kalantzopoulos, Georgios N.; Wragg, David; Arstad, Bjørnar; Blom, Richard & Sjåstad, Anja Olafsen [Vis alle 7 forfattere av denne artikkelen] (2017). Thermogravimetric analysis – a viable method for screening materials for the SEWGS process.
• Kalantzopoulos, Georgios N.; Lundvall, Fredrik; Hill, Adam; Lind, Anna Maria; Arstad, Bjørnar & Attfield, Martin P. [Vis alle 9 forfattere av denne artikkelen] (2017). CATalyst transformations and LIFEtime by in-situ techniques and modelling (CATLIFE).
• Kalantzopoulos, Georgios N.; Lundvall, Fredrik; Lind, Anna Maria; Arstad, Bjørnar; Chernyshov, Dmitry & Wragg, David [Vis alle 7 forfattere av denne artikkelen] (2017). High time-resolution in-situ methods for tracking structural transformations in SAPO materials.
• Wragg, David; Sottmann, Jonas; Vajeeston, Ponniah; Sørby, Magnus Helgerud & Fjellvåg, Helmer (2016). Does the 3D Topological Dirac Semimetal Na3P Have More Than One Ground State?
• Lundvall, Fredrik; Kalantzopoulos, Georgios N.; Wragg, David; Arstad, Bjørnar; Blom, Richard & Sjåstad, Anja Olafsen [Vis alle 7 forfattere av denne artikkelen] (2016). Thermogravimetric analysis – a viable method for screening materials for the SEWGS process.
• Wragg, David; Sottmann, Jonas; Vajeeston, Ponniah; Emerich, Hermann; Fjellvåg, Helmer & Hermann, Matthias [Vis alle 9 forfattere av denne artikkelen] (2016). Size Matters: How crystallite size controls reaction path in the sodium bismuth anode system.
• Strandbakke, Ragnar; Vøllestad, Einar; Prato, Rafael Alberto; Wragg, David; Sartori, Sabrina & Norby, Truls (2016). Structural and electrochemical properties of hydrated mixed conductor Ba1-xGd0.8La0.2+xCo2O6-d.
• Brennhagen, Anders; Cavallo, Carmen; Wragg, David Stephen; Ponniah, Vajeeston; Sjåstad, Anja Olafsen & Fjellvåg, Helmer (2024). Bi metallates as conversion-alloying anodes for Na-ion batteries. Universitetet i Oslo.
• Thiagarajan, Abilash Kanish; Brennhagen, Anders; Wragg, David Stephen & Koposov, Alexey (2023). Structural changes in graphite-based anodes of Li-ion batteries elucidated through operando XRD. Kjemisk Institutt. Vis sammendrag

  Lithium-ion batteries (LIBs) with graphite-based anodes dominate the battery market around the world and have been studied extensively for the past decades, but the structural changes during cycling are still not fully understood. In this work, we used galvanostatic cycling (GC) to characterize the electrochemical performance of graphite samples in LIB. We also attempted to achieve stable capacities over hundreds of cycles to monitor the effect of long-term cycling on the mechanisms of graphite, with limited success. The fabricated coin cells experienced poor capacity retention across all graphite samples and some abnormal capacity increases that had not been observed previously. We noticed that electrolytes containing FEC made a noticeable change to the electrochemical performance as it resulted in irregular cycling, but also better capacity retention. Operando X-ray diffraction is a powerful technique to understand structural changes. We looked at multiple graphite reflections, mainly 002, 100, 101, 102 and 004, and observed that the expansion of the structure is not only 2 dimensions but all 3 dimensions as the interlayer distance and graphene layers expands during lithiation. We also monitored this expansion of graphene layers with pair distribution function (PDF) as the three C-C distances in hexagonal carbon rings, 1.41 Å, 2.41 Å and 2.85 Å, changed lengths at different points during lithiation and delithiation. We looked at diffraction peaks during lithiation and delithiation to study the mechanisms and observed that they were different. Lithiation showed solid solution like behavior indicating disordered intermediate phases, while delithiation showed two-phase transition indicating ordered structures. In this work we have used Operando X-ray diffraction to show that the structural changes graphite undergoes during cycling, transition from graphite to LiC6, is not specific to each graphite sample and the structural changes depend on the condition of the material. Pristine graphite samples transitioned fully to LiC6 during cycling with C-rate of C/6, but only LiC12 when a higher C-rate of C/2 was used. Graphite electrodes cut from commercial pouch cells that had cycled many hundreds of electrochemical cycles were able to transition to LiC6 during C/20, but only LiC12 during C/6, indicating an “ageing” mechanism.

• Sottmann, Jonas; Fjellvåg, Helmer; Wragg, David & Sartori, Sabrina (2017). Synchrotron Based Operando Methods for Characterization of Non-Aqueous Rechargeable Battery Electrode Materials. Universitetet i Oslo.

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