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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I05-ARPES
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Ryo
Noguchi
,
Masaru
Kobayashi
,
Zhanzhi
Jiang
,
Kenta
Kuroda
,
Takanari
Takahashi
,
Zifan
Xu
,
Daehun
Lee
,
Motoaki
Hirayama
,
Masayuki
Ochi
,
Tetsuroh
Shirasawa
,
Peng
Zhang
,
Chun
Lin
,
Cédric
Bareille
,
Shunsuke
Sakuragi
,
Hiroaki
Tanaka
,
So
Kunisada
,
Kifu
Kurokawa
,
Koichiro
Yaji
,
Ayumi
Harasawa
,
Viktor
Kandyba
,
Alessio
Giampietri
,
Alexei
Barinov
,
Timur K.
Kim
,
Cephise
Cacho
,
Makoto
Hashimoto
,
Donghui
Lu
,
Shik
Shin
,
Ryotaro
Arita
,
Keji
Lai
,
Takao
Sasagawa
,
Takeshi
Kondo
Diamond Proposal Number(s):
[20445]
Abstract: Low-dimensional van der Waals materials have been extensively studied as a platform with which to generate quantum effects. Advancing this research, topological quantum materials with van der Waals structures are currently receiving a great deal of attention. Here, we use the concept of designing topological materials by the van der Waals stacking of quantum spin Hall insulators. Most interestingly, we find that a slight shift of inversion centre in the unit cell caused by a modification of stacking induces a transition from a trivial insulator to a higher-order topological insulator. Based on this, we present angle-resolved photoemission spectroscopy results showing that the real three-dimensional material Bi4Br4 is a higher-order topological insulator. Our demonstration that various topological states can be selected by stacking chains differently, combined with the advantages of van der Waals materials, offers a playground for engineering topologically non-trivial edge states towards future spintronics applications.
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Jan 2021
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I15-1-X-ray Pair Distribution Function (XPDF)
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Xiao
Hua
,
Alexander S.
Eggeman
,
Elizabeth
Castillo-Martinez
,
Rosa
Robert
,
Harry S.
Geddes
,
Ziheng
Lu
,
Chris J.
Pickard
,
Wei
Meng
,
Kamila M.
Wiaderek
,
Nathalie
Pereira
,
Glenn G.
Amatucci
,
Paul A.
Midgley
,
Karena W.
Chapman
,
Ullrich
Steiner
,
Andrew L.
Goodwin
,
Clare
Grey
Diamond Proposal Number(s):
[17315]
Abstract: Metal fluorides, promising lithium-ion battery cathode materials, have been classified as conversion materials due to the reconstructive phase transitions widely presumed to occur upon lithiation. We challenge this view by studying FeF3 using X-ray total scattering and electron diffraction techniques that measure structure over multiple length scales coupled with density functional theory calculations, and by revisiting prior experimental studies of FeF2 and CuF2. Metal fluoride lithiation is instead dominated by diffusion-controlled displacement mechanisms, and a clear topological relationship between the metal fluoride F− sublattices and that of LiF is established. Initial lithiation of FeF3 forms FeF2 on the particle’s surface, along with a cation-ordered and stacking-disordered phase, A-LixFeyF3, which is structurally related to α-/β-LiMn2+Fe3+F6 and which topotactically transforms to B- and then C-LixFeyF3, before forming LiF and Fe. Lithiation of FeF2 and CuF2 results in a buffer phase between FeF2/CuF2 and LiF. The resulting principles will aid future developments of a wider range of isomorphic metal fluorides.
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Jan 2021
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B18-Core EXAFS
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Gustav W.
Sievers
,
Anders W.
Jensen
,
Jonathan
Quinson
,
Alessandro
Zana
,
Francesco
Bizzotto
,
Mehtap
Oezaslan
,
Alexandra
Dworzak
,
Jacob J. K.
Kirkensgaard
,
Thomas E. L.
Smitshuysen
,
Shima
Kadkhodazadeh
,
Mikkel
Juelsholt
,
Kirsten M. Ø.
Jensen
,
Kirsten
Anklam
,
Hao
Wan
,
Jan
Schäfer
,
Klára
Čépe
,
María
Escudero-Escribano
,
Jan
Rossmeisl
,
Antje
Quade
,
Volker
Brüser
,
Matthias
Arenz
Diamond Proposal Number(s):
[12746]
Abstract: Several concepts for platinum-based catalysts for the oxygen reduction reaction (ORR) are presented that exceed the US Department of Energy targets for Pt-related ORR mass activity. Most concepts achieve their high ORR activity by increasing the Pt specific activity at the expense of a lower electrochemically active surface area (ECSA). In the potential region controlled by kinetics, such a lower ECSA is counterbalanced by the high specific activity. At higher overpotentials, however, which are often applied in real systems, a low ECSA leads to limitations in the reaction rate not by kinetics, but by mass transport. Here we report on self-supported platinum–cobalt oxide networks that combine a high specific activity with a high ECSA. The high ECSA is achieved by a platinum–cobalt oxide bone nanostructure that exhibits unprecedentedly high mass activity for self-supported ORR catalysts. This concept promises a stable fuel-cell operation at high temperature, high current density and low humidification.
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Aug 2020
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I11-High Resolution Powder Diffraction
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Chao
Xu
,
Katharina
Märker
,
Juhan
Lee
,
Amoghavarsha
Mahadevegowda
,
Philip J.
Reeves
,
Sarah J.
Day
,
Matthias F.
Groh
,
Steffen P.
Emge
,
Caterina
Ducati
,
B. Layla
Mehdi
,
Chiu C.
Tang
,
Clare P.
Grey
Diamond Proposal Number(s):
[16733, 25186]
Abstract: Ni-rich layered cathode materials are among the most promising candidates for high-energy-density Li-ion batteries, yet their degradation mechanisms are still poorly understood. We report a structure-driven degradation mechanism for NMC811 (LiNi0.8Mn0.1Co0.1O2), in which a proportion of the material exhibits a lowered accessible state of charge at the end of charging after repetitive cycling and becomes fatigued. Operando synchrotron long-duration X-ray diffraction enabled by a laser-thinned coin cell shows the emergence and growth in the concentration of this fatigued phase with cycle number. This degradation is structure driven and is not solely due to kinetic limitations or intergranular cracking: no bulk phase transformations, no increase in Li/Ni antisite mixing and no notable changes in the local structure or Li-ion mobility of the bulk are seen in aged NMCs. Instead, we propose that this degradation stems from the high interfacial lattice strain between the reconstructed surface and the bulk layered structure that develops when the latter is at states of charge above a distinct threshold of approximately 75%. This mechanism is expected to be universal in Ni-rich layered cathodes. Our findings provide fundamental insights into strategies to help mitigate this degradation process.
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Aug 2020
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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M.
Hepting
,
D.
Li
,
C. J.
Jia
,
H.
Lu
,
E.
Paris
,
Y.
Tseng
,
X.
Feng
,
M.
Osada
,
E.
Been
,
Y.
Hikita
,
Y.-D.
Chuang
,
Z.
Hussain
,
K. J.
Zhou
,
A.
Nag
,
M.
Garcia-Fernandez
,
M.
Rossi
,
H. Y.
Huang
,
D. J.
Huang
,
Z. X.
Shen
,
T.
Schmitt
,
H. Y.
Hwang
,
B.
Moritz
,
J.
Zaanen
,
T. P.
Devereaux
,
W. S.
Lee
Diamond Proposal Number(s):
[22009]
Abstract: The search continues for nickel oxide-based materials with electronic properties similar to cuprate high-temperature superconductors. The recent discovery of superconductivity in the doped infinite-layer nickelate NdNiO2 has strengthened these efforts. Here, we use X-ray spectroscopy and density functional theory to show that the electronic structure of LaNiO2 and NdNiO2, while similar to the cuprates, includes significant distinctions. Unlike cuprates, the rare-earth spacer layer in the infinite-layer nickelate supports a weakly interacting three-dimensional 5d metallic state, which hybridizes with a quasi-two-dimensional, strongly correlated state with
3
d
x
2
−
y
2
3dx2−y2
symmetry in the NiO2 layers. Thus, the infinite-layer nickelate can be regarded as a sibling of the rare-earth intermetallics, which are well known for heavy fermion behaviour, where the NiO2 correlated layers play an analogous role to the 4f states in rare-earth heavy fermion compounds. This Kondo- or Anderson-lattice-like ‘oxide-intermetallic’ replaces the Mott insulator as the reference state from which superconductivity emerges upon doping.
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Jan 2020
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