I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[31498]
Open Access
Abstract: By virtue of their open network structures and low densities, metal–organic frameworks (MOFs) are soft materials that exhibit elastic instabilities at low applied stresses. The conventional strategy for improving elastic stability is to increase the connectivity of the underlying MOF network, which necessarily increases the material density and reduces the porosity. Here we demonstrate an alternative paradigm, whereby elastic stability is enhanced in a MOF with an aperiodic network topology. We use a combination of variable-pressure single-crystal X-ray diffraction measurements and coarse-grained lattice-dynamical calculations to interrogate the high-pressure behaviour of the topologically aperiodic system TRUMOF-1, which we compare against that of its ordered congener MOF-5. We show that the topology of the former quenches the elastic instability responsible for pressure-induced framework collapse in the latter, much as irregularity in the shapes and sizes of stones acts to prevent cooperative mechanical failure in drystone walls. Our results establish aperiodicity as a counter-intuitive design motif in engineering the mechanical properties of framework structures that is relevant to MOFs and larger-scale architectures alike.
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Jul 2024
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I07-Surface & interface diffraction
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Dionisius H. L.
Tjhe
,
Xinglong
Ren
,
Ian
Jacobs
,
Gabriele
D'Avino
,
Tarig B. E.
Mustafa
,
Thomas G.
Marsh
,
Lu
Zhang
,
Yao
Fu
,
Ahmed E.
Mansour
,
Andreas
Opitz
,
Yuxuan
Huang
,
Wenjin
Zhu
,
Ahmet Hamdi
Unal
,
Sebastiaan
Hoek
,
Vincent
Lemaur
,
Claudio
Quarti
,
Qiao
He
,
Jin-Kyun
Lee
,
Iain
Mcculloch
,
Martin
Heeney
,
Norbert
Koch
,
Clare P.
Grey
,
David
Beljonne
,
Simone
Fratini
,
Henning
Sirringhaus
Diamond Proposal Number(s):
[30708, 30349]
Open Access
Abstract: Conducting polymers are mixed ionic–electronic conductors that are emerging candidates for neuromorphic computing, bioelectronics and thermoelectrics. However, fundamental aspects of their many-body correlated electron–ion transport physics remain poorly understood. Here we show that in p-type organic electrochemical transistors it is possible to remove all of the electrons from the valence band and even access deeper bands without degradation. By adding a second, field-effect gate electrode, additional electrons or holes can be injected at set doping states. Under conditions where the counterions are unable to equilibrate in response to field-induced changes in the electronic carrier density, we observe surprising, non-equilibrium transport signatures that provide unique insights into the interaction-driven formation of a frozen, soft Coulomb gap in the density of states. Our work identifies new strategies for substantially enhancing the transport properties of conducting polymers by exploiting non-equilibrium states in the coupled system of electronic charges and counterions.
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Jul 2024
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Diamond Proposal Number(s):
[25785]
Open Access
Abstract: Oxygen redox cathodes, such as Li1.2Ni0.13Co0.13Mn0.54O2, deliver higher energy densities than those based on transition metal redox alone. However, they commonly exhibit voltage fade, a gradually diminishing discharge voltage on extended cycling. Recent research has shown that, on the first charge, oxidation of O2− ions forms O2 molecules trapped in nano-sized voids within the structure, which can be fully reduced to O2− on the subsequent discharge. Here we show that the loss of O-redox capacity on cycling and therefore voltage fade arises from a combination of a reduction in the reversibility of the O2−/O2 redox process and O2 loss. The closed voids that trap O2 grow on cycling, rendering more of the trapped O2 electrochemically inactive. The size and density of voids leads to cracking of the particles and open voids at the surfaces, releasing O2. Our findings implicate the thermodynamic driving force to form O2 as the root cause of transition metal migration, void formation and consequently voltage fade in Li-rich cathodes.
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Mar 2024
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S.
Zhang
,
J.
Deliyore-Ramírez
,
S.
Deng
,
B.
Nair
,
D.
Pesquera
,
Q.
Jing
,
M. E.
Vickers
,
S.
Crossley
,
M.
Ghidini
,
G. G.
Guzmán-Verri
,
X.
Moya
,
N. D.
Mathur
Open Access
Abstract: Electrocaloric effects have been experimentally studied in ferroelectrics and incipient ferroelectrics, but not incipient ferroelectrics driven ferroelectric using strain. Here we use optimally oriented interdigitated surface electrodes to investigate extrinsic electrocaloric effects in low-loss epitaxial SrTiO3 films near the broad second-order 243 K ferroelectric phase transition created by biaxial in-plane coherent tensile strain from DyScO3 substrates. Our extrinsic electrocaloric effects are an order of magnitude larger than the corresponding effects in bulk SrTiO3 over a wide range of temperatures including room temperature, and unlike electrocaloric effects associated with first-order transitions they are highly reversible in unipolar applied fields. Additionally, the canonical Landau description for strained SrTiO3 films works well if we set the low-temperature zero-field polarization along one of the in-plane pseudocubic <100> directions. In future, similar strain engineering could be exploited for other films, multilayers and bulk samples to increase the range of electrocaloric materials for energy efficient cooling.
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Mar 2024
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I15-1-X-ray Pair Distribution Function (XPDF)
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Open Access
Abstract: Membranes with ultrahigh permeance and practical selectivity could greatly decrease the cost of difficult industrial gas separations, such as CH4/N2 separation. Advanced membranes made from porous materials, such as metal–organic frameworks, can achieve a good gas separation performance, although they are typically formed on support layers or mixed with polymeric matrices, placing limitations on gas permeance. Here an amorphous glass foam, agfZIF-62, wherein a, g and f denote amorphous, glass and foam, respectively, was synthesized by a polymer-thermal-decomposition-assisted melting strategy, starting from a crystalline zeolitic imidazolate framework, ZIF-62. The thermal decomposition of incorporated low-molecular-weight polyethyleneimine evolves CO2, NH3 and H2O gases, creating a large number and variety of pores. This greatly increases pore interconnectivity but maintains the crystalline ZIF-62 ultramicropores, allowing ultrahigh gas permeance and good selectivity. A self-supported circular agfZIF-62 with a thickness of 200–330 µm and area of 8.55 cm2 was used for membrane separation. The membranes perform well, showing a CH4 permeance of 30,000–50,000 gas permeance units, approximately two orders of magnitude higher than that of other reported membranes, with good CH4/N2 selectivity (4–6).
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May 2023
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Charles C.
Tam
,
Jaewon
Choi
,
Xiang
Ding
,
Stefano
Agrestini
,
Abhishek
Nag
,
Mei
Wu
,
Bing
Huang
,
Huiqian
Luo
,
Peng
Gao
,
Mirian
Garcia-Fernandez
,
Liang
Qiao
,
Ke-Jin
Zhou
Diamond Proposal Number(s):
[30296]
Abstract: In materials science, much effort has been devoted to the reproduction of superconductivity in chemical compositions, analogous to cuprate superconductors since their discovery over 30 years ago. This approach was recently successful in realising superconductivity in infinite-layer nickelates1,2,3,4,5,6. Although differing from cuprates in electronic and magnetic properties, strong Coulomb interactions suggest that infinite-layer nickelates have a propensity towards various symmetry-breaking orders that populate cuprates7,8,9,10. Here we report the observation of charge density waves (CDWs) in infinite-layer NdNiO2 films using Ni L3 resonant X-ray scattering. Remarkably, CDWs form in Nd 5d and Ni 3d orbitals at the same commensurate wavevector (0.333, 0) reciprocal lattice units, with non-negligible out-of-plane dependence and an in-plane correlation length of up to ~60 Å. Spectroscopic studies reveal a strong connection between CDWs and Nd 5d–Ni 3d orbital hybridization. Upon entering the superconducting state at 20% Sr doping, the CDWs disappear. Our work demonstrates the existence of CDWs in infinite-layer nickelates with a multiorbital character distinct from cuprates, which establishes their low-energy physics.
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Aug 2022
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B22-Multimode InfraRed imaging And Microspectroscopy
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Bing
An
,
Zhe
Li
,
Zi
Wang
,
Xiangdi
Zeng
,
Xue
Han
,
Yongqiang
Chen
,
Alena M.
Sheveleva
,
Zhongyue
Zhang
,
Floriana
Tuna
,
Eric J. L.
Mcinnes
,
Mark D.
Frogley
,
Anibal J.
Ramirez-Cuesta
,
Louise S.
Natrajan
,
Cheng
Wang
,
Wenbin
Li
,
Sihai
Yang
,
Martin
Schroeder
Diamond Proposal Number(s):
[23782]
Abstract: Natural gas, consisting mainly of methane (CH4), has a relatively low energy density at ambient conditions (~36 kJ l−1). Partial oxidation of CH4 to methanol (CH3OH) lifts the energy density to ~17 MJ l−1 and drives the production of numerous chemicals. In nature, this is achieved by methane monooxygenase with di-iron sites, which is extremely challenging to mimic in artificial systems due to the high dissociation energy of the C–H bond in CH4 (439 kJ mol−1) and facile over-oxidation of CH3OH to CO and CO2. Here we report the direct photo-oxidation of CH4 over mono-iron hydroxyl sites immobilized within a metal–organic framework, PMOF-RuFe(OH). Under ambient and flow conditions in the presence of H2O and O2, CH4 is converted to CH3OH with 100% selectivity and a time yield of 8.81 ± 0.34 mmol gcat−1 h−1 (versus 5.05 mmol gcat−1 h−1 for methane monooxygenase). By using operando spectroscopic and modelling techniques, we find that confined mono-iron hydroxyl sites bind CH4 by forming an [Fe–OH···CH4] intermediate, thus lowering the barrier for C–H bond activation. The confinement of mono-iron hydroxyl sites in a porous matrix demonstrates a strategy for C–H bond activation in CH4 to drive the direct photosynthesis of CH3OH.
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Jun 2022
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I07-Surface & interface diffraction
I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[24359, 23666]
Open Access
Abstract: Membranes with high selectivity offer an attractive route to molecular separations, where technologies such as distillation and chromatography are energy intensive. However, it remains challenging to fine tune the structure and porosity in membranes, particularly to separate molecules of similar size. Here, we report a process for producing composite membranes that comprise crystalline porous organic cage films fabricated by interfacial synthesis on a polyacrylonitrile support. These membranes exhibit ultrafast solvent permeance and high rejection of organic dyes with molecular weights over 600 g mol−1. The crystalline cage film is dynamic, and its pore aperture can be switched in methanol to generate larger pores that provide increased methanol permeance and higher molecular weight cut-offs (1,400 g mol−1). By varying the water/methanol ratio, the film can be switched between two phases that have different selectivities, such that a single, ‘smart’ crystalline membrane can perform graded molecular sieving. We exemplify this by separating three organic dyes in a single-stage, single-membrane process.
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Jan 2022
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E02-JEM ARM 300CF
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Yi-Chao
Zou
,
Lucas
Mogg
,
Nick
Clark
,
Cihan
Bacaksiz
,
Slavisa
Milanovic
,
Vishnu
Sreepal
,
Guang-Ping
Hao
,
Yi-Chi
Wang
,
David G.
Hopkinson
,
Roman
Gorbachev
,
Samuel
Shaw
,
Kostya S.
Novoselov
,
Rahul
Raveendran-Nair
,
Francois M.
Peeters
,
Marcelo
Lozada-Hidalgo
,
Sarah
Haigh
Diamond Proposal Number(s):
[21981, 21597]
Abstract: The physical properties of clays and micas can be controlled by exchanging ions in the crystal lattice. Atomically thin materials can have superior properties in a range of membrane applications, yet the ion-exchange process itself remains largely unexplored in few-layer crystals. Here we use atomic-resolution scanning transmission electron microscopy to study the dynamics of ion exchange and reveal individual ion binding sites in atomically thin and artificially restacked clays and micas. We find that the ion diffusion coefficient for the interlayer space of atomically thin samples is up to 104 times larger than in bulk crystals and approaches its value in free water. Samples where no bulk exchange is expected display fast exchange at restacked interfaces, where the exchanged ions arrange in islands with dimensions controlled by the moiré superlattice dimensions. We attribute the fast ion diffusion to enhanced interlayer expandability resulting from weaker interlayer binding forces in both atomically thin and restacked materials. This work provides atomic scale insights into ion diffusion in highly confined spaces and suggests strategies to design exfoliated clay membranes with enhanced performance.
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Aug 2021
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I12-JEEP: Joint Engineering, Environmental and Processing
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Ziyang
Ning
,
Dominic Spencer
Jolly
,
Guanchen
Li
,
Robin
De Meyere
,
Shengda D.
Pu
,
Yang
Chen
,
Jitti
Kasemchainan
,
Johannes
Ihli
,
Chen
Gong
,
Boyang
Liu
,
Dominic L. R.
Melvin
,
Anne
Bonnin
,
Oxana
Magdysyuk
,
Paul
Adamson
,
Gareth O.
Hartley
,
Charles W.
Monroe
,
James
Marrow
,
Peter G.
Bruce
Diamond Proposal Number(s):
[20795]
Abstract: Lithium dendrite (filament) propagation through ceramic electrolytes, leading to short circuits at high rates of charge, is one of the greatest barriers to realizing high-energy-density all-solid-state lithium-anode batteries. Utilizing in situ X-ray computed tomography coupled with spatially mapped X-ray diffraction, the propagation of cracks and the propagation of lithium dendrites through the solid electrolyte have been tracked in a Li/Li6PS5Cl/Li cell as a function of the charge passed. On plating, cracking initiates with spallation, conical ‘pothole’-like cracks that form in the ceramic electrolyte near the surface with the plated electrode. The spallations form predominantly at the lithium electrode edges where local fields are high. Transverse cracks then propagate from the spallations across the electrolyte from the plated to the stripped electrode. Lithium ingress drives the propagation of the spallation and transverse cracks by widening the crack from the rear; that is, the crack front propagates ahead of the Li. As a result, cracks traverse the entire electrolyte before the Li arrives at the other electrode, and therefore before a short circuit occurs.
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Apr 2021
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