B18-Core EXAFS
I11-High Resolution Powder Diffraction
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Pu
Zhao
,
Lin
Ye
,
Guangchao
Li
,
Chen
Huang
,
Simson
Wu
,
Ping-Luen
Ho
,
Haokun
Wang
,
Tatchamapan
Yoskamtorn
,
Denis
Sheptyakov
,
Giannantonio
Cibin
,
Angus I.
Kirkland
,
Chiu C.
Tang
,
Anmin
Zheng
,
Wenjuan
Xue
,
Donghai
Mei
,
Kongkiat
Suriye
,
Shik Chi Edman
Tsang
Abstract: Synthesizing atomically dispersed synergistic active pairs is crucial yet challenging in developing highly active heterogeneous catalysts for various industrially important reactions. Here, a single molecular Re species is immobilized on the inner surface of a Y zeolite with Brønsted acid sites (BASs) within atomic proximity to form Re OMS–BAS active pairs for the efficient catalysis of olefin metathesis reactions (OMS: olefin metathesis site). The synergy within the active pairs is revealed by studying the coadsorption geometry of the olefin substrates over the active pairs by synchrotron X-ray and neutron powder diffraction. It is shown that the BAS not only facilitates olefin adsorption but also aligns the olefin molecule to the Re OMS for efficient intermediate formation. Consequently, for the cross-metathesis of ethene and trans-2-butene to propene, this catalyst shows high activity under mild reaction conditions without observable deactivation. The catalyst outperforms not only traditional ReOx-based catalysts but also the best industrially applicable WOx-based catalyst thus far that we discovered previously. The concept of using two isolated active sites of different functionalities within atomic proximity in a confined cavity can provide opportunities for designing synergistically catalytic materials.
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Mar 2021
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I11-High Resolution Powder Diffraction
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Tatchamapan
Yoskamtorn
,
Pu
Zhao
,
Xin-Ping
Wu
,
Kirsty
Purchase
,
Fabio
Orlandi
,
Pascal
Manuel
,
James
Taylor
,
Yiyang
Li
,
Sarah
Day
,
Lin
Ye
,
Chiu C.
Tang
,
Yufei
Zhao
,
S. C. Edman
Tsang
Abstract: Understanding structural responses of metal–organic frameworks (MOFs) to external stimuli such as the inclusion of guest molecules and temperature/pressure has gained increasing attention in many applications, for example, manipulation and manifesto smart materials for gas storage, energy storage, controlled drug delivery, tunable mechanical properties, and molecular sensing, to name but a few. Herein, neutron and synchrotron diffractions along with Rietveld refinement and density functional theory calculations have been used to elucidate the responsive adsorption behaviors of defect-rich Zr-based MOFs upon the progressive incorporation of ammonia (NH3) and variable temperature. UiO-67 and UiO-bpydc containing biphenyl dicarboxylate and bipyridine dicarboxylate linkers, respectively, were selected, and the results establish the paramount influence of the functional linkers on their NH3 affinity, which leads to stimulus-tailoring properties such as gate-controlled porosity by dynamic linker flipping, disorder, and structural rigidity. Despite their structural similarities, we show for the first time the dramatic alteration of NH3 adsorption profiles when the phenyl groups are replaced by the bipyridine in the organic linker. These molecular controls stem from controlling the degree of H-bonding networks/distortions between the bipyridine scaffold and the adsorbed NH3 without significant change in pore volume and unit cell parameters. Temperature-dependent neutron diffraction also reveals the NH3-induced rotational motions of the organic linkers. We also demonstrate that the degree of structural flexibility of the functional linkers can critically be affected by the type and quantity of the small guest molecules. This strikes a delicate control in material properties at the molecular level.
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Feb 2021
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I11-High Resolution Powder Diffraction
I15-1-X-ray Pair Distribution Function (XPDF)
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Tianyi
Chen
,
Ieuan
Ellis
,
Thomas
Hooper
,
Emanuela
Liberti
,
Lin
Ye
,
Tsz Woon Benedict
Lo
,
Colum
O'Leary
,
Alexandra A.
Sheader
,
Gerardo T.
Martinez
,
Lewys
Jones
,
Ping-Luen
Ho
,
Pu
Zhao
,
James
Cookson
,
Peter T
Bishop
,
Philip A.
Chater
,
John V.
Hanna
,
Peter D.
Nellist
,
Shik Chi Edman
Tsang
Diamond Proposal Number(s):
[15452]
Abstract: It is well established that the inclusion of small atomic species such as boron (B) in powder metal catalysts can subtly modify catalytic properties, and the associated changes in the metal lattice implies that the B atoms are located in the interstitial sites. However, there is no compelling evidence for the occurrence of interstitial B atoms, and there is a concomitant lack of detailed structural information describing the nature of this occupancy and its effects on the metal host. In this work, we use an innovative combination of high-resolution 11B magic-angle-spinning (MAS) and 105Pd static solid state NMR nuclear magnetic resonance (NMR), synchrotron X-ray diffraction (SXRD), in-situ X-ray pair distribution function (XPDF), scanning transmission electron microscopy-annular dark field imaging (STEM-ADF), electron ptychography and electron energy loss spectroscopy (EELS) to investigate the B atom positions, properties and structural modifications to the palladium lattice of an industrial type interstitial boron doped palladium nanoparticle catalyst system (Pd-intB/C NPs). In this study we report that upon B incorporation into the Pd lattice, the overall face centered cubic (FCC) lattice is maintained, however short range disorder is introduced. The 105Pd static solid-state NMR illustrates how different types (and levels) of structural strain and disorder are introduced in the nanoparticle history. These structural distortions can lead to the appearance of small amounts of local hexagonal close packed (HCP) structured material in localized regions. The short range lattice tailoring of the Pd framework to accommodate interstitial B dopants in the octahedral sites of the distorted FCC structure can be imaged by electron ptychography. This study describes new toolsets that enables the characterization of industrial metal nanocatalysts across length scales from macro-analysis to micro-analysis, which gives important guidance to structure-activity relationship of the system.
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Nov 2019
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I11-High Resolution Powder Diffraction
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Zhenping
Cai
,
Jinxing
Long
,
Yingwen
Li
,
Lin
Ye
,
Biaolin
Yin
,
Liam John
France
,
Juncai
Dong
,
Lirong
Zheng
,
Hongyan
He
,
Sijie
Liu
,
Shik Chi Edman
Tsang
,
Xuehui
Li
Open Access
Abstract: Green production of bulk chemicals traditionally obtained from fossil resources is of great importance. One potential route toward realizing this goal is through the utilization of renewable lignin; however, current techniques generally lead to low product specificity because of the structural diversity of this recalcitrant biopolymer. Herein, we devised a new catalytic system to promote selectively oxidative lignin in air, and diethyl maleate was formed at impressively high yield of 404.8 mg g−1 and selectivity of 72.7% over the polyoxometalate ionic liquid of [BSmim]CuPW12O40. This high catalytic activity is ascribed to a five-coordinated Cu+ species, which, through the formation of end-on dioxygen species in vacant orbitals, facilitates the selective oxidation of basic lignin aromatic units (phenylpropane C9 units). Therefore, these results represent significant progress toward the realization of an industrially applicable and highly selective lignin oxidation process for the generation of value-added and bulk chemicals.
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Jun 2019
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E01-JEM ARM 200CF
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Lin
Ye
,
A. A. Hanif
Mahadi
,
Chalathan
Saengruengrit
,
Jin
Qu
,
Feng
Xu
,
Simon
Fairclough
,
Neil
Young
,
Ping-Luen
Ho
,
Junjun
Shan
,
Luan
Nguyen
,
Franklin F.
Tao
,
Karaked
Tedsree
,
Shik Chi Edman
Tsang
Abstract: Ceria has been widely used as support in electrocatalysis for its high degree of oxygen storage, fast oxygen mobility and reduction and oxidation properties at mild conditions. However, it is unclear what are the underlying principles and the nature of surface involved. By controlling the growth of various morphologies of ceria nanoparticles, it is demonstrated that the cubic-form of ceria, predominantly covered with higher energy polar surface (100), as support for Pd gives much higher activity in the electrocatalytic oxidation of formic acid than ceria of other morphologies (rods and spheres) with low indexed facets ((110) and (111)). High resolution TEM confirms the alternating layer-to-layer of cations and anions in (100) surface, the electrostatic repulsion of oxygen anions within the same layers gives intrinsically higher oxygen vacancies on this redox active surface in order to reduce surface polarity. DFT calculations suggest that the properties of fast oxygen mobility to re-oxidize the CO-poisoned Pd may arise from the overdosed oxygens on these ceria surface layers during electro-oxidation hence sustaining higher activity.
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Apr 2019
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I11-High Resolution Powder Diffraction
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Lin
Ye
,
Xinping
Duan
,
Simson
Wu
,
Tai-Sing
Wu
,
Yuxin
Zhao
,
Alex W.
Robertson
,
Hung-Lung
Chou
,
Jianwei
Zheng
,
Tugce
Ayvali
,
Sarah
Day
,
Chiu
Tang
,
Yun-Liang
Soo
,
Youzhu
Yuan
,
Shik Chi Edman
Tsang
Open Access
Abstract: Replacement of Hg with non-toxic Au based catalysts for industrial hydrochlorination of acetylene to vinyl chloride is urgently required. However Au catalysts suffer from progressive deactivation caused by auto-reduction of Au(I) and Au(III) active sites and irreversible aggregation of Au(0) inactive sites. Here we show from synchrotron X-ray absorption, STEM imaging and DFT modelling that the availability of ceria(110) surface renders Au(0)/Au(I) as active pairs. Thus, Au(0) is directly involved in the catalysis. Owing to the strong mediating properties of Ce(IV)/Ce(III) with one electron complementary redox coupling reactions, the ceria promotion to Au catalysts gives enhanced activity and stability. Total pre-reduction of Au species to inactive Au nanoparticles of Au/CeO2&AC when placed in a C2H2/HCl stream can also rapidly rejuvenate. This is dramatically achieved by re-dispersing the Au particles to Au(0) atoms and oxidising to Au(I) entities, whereas Au/AC does not recover from the deactivation.
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Feb 2019
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B18-Core EXAFS
I11-High Resolution Powder Diffraction
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Tugce
Ayvali
,
Lin
Ye
,
Simson
Wu
,
Benedict T. W.
Lo
,
Chen
Huang
,
Bin
Yu
,
Giannantonio
Cibin
,
Angus I.
Kirkland
,
Chiu
Tang
,
Abdulaziz A.
Bagabas
,
S. C. Edman
Tsang
Diamond Proposal Number(s):
[16358, 14647]
Abstract: Deposition of gold on supports can produce catalytically active forms of gold as well as spectators, but previous understanding of the nature of active immobilized precursors is poor. By using synchrotron X-ray powder diffraction (SXRD) and X-ray absorption spectroscopy (XAS) techniques, we report a novel synthesis and structural elucidation of atomically dispersed gold species anchored to the internal surface of TS-1 as K+Au(OH)2Na+(Of)3 (“f” signifies the framework atoms of TS-1 in the formula.). It is found that the choice of alkali ions plays a crucial role in nucleation and stabilization of the atomic precursor. These anchored single Au upon controlled reduction in H2 can form uniform gold clusters in direct contact with the TS-1 surface containing isolated Ti sites: their interface exhibits excellent specificity and stability towards epoxidation of propylene in H2/O2 due to synergetic effect.
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Nov 2018
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I11-High Resolution Powder Diffraction
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Abstract: Gamma‐valerolactone (GVL) is regarded as a key platform molecule in the production of fine chemicals such as pentenoic acid (PA) from biomass. Although PA is believed to be the key intermediate in solid acid catalyzed reactions of GVL, due to subsequent facile decarboxylation reactions, further alkene products were formed. Here, by tailoring the acidity of Brønsted acid sites in an alumino‐phosphate (AlPO) molecular sieve via incorporation of Zn2+ into the framework, we access a new selective, high yield catalytic route for GVL conversion to PA.
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Oct 2018
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I11-High Resolution Powder Diffraction
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Abstract: Using synchrotron X-ray powder diffraction-mass spectrometry in combination with theoretical calculations, we probed the structural changes of adsorbed methanol species in H-ZSM-5 for the first time during catalytic conversion of methanol. Preliminary experimental and computational findings suggested that associative mechanism was the dominant reaction pathway in the early stage of the reaction at 200 °C. Also, we observed a minor contribution from dissociative mechanism of the adsorbed methoxy intermediate species, CH3-Oz (where Oz is a framework oxygen atom), at Brønsted acid sites. It led to methoxy accumulation during the late stage of the reaction, which was postulated to be the initial step that produced ‘hydrocarbon pool’ and ‘coke’ through the formation of CC bonds.
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Sep 2018
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I11-High Resolution Powder Diffraction
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Abstract: Synchrotron X-ray powder diffraction has begun to stretch its strategic presence from the sheer determination of crystal structures into the mechanistic and kinetic information of microporous zeolite materials. Not only can this technique be used to reveal the internal framework structure of zeolites and their active sites, but it can also be combined with other analytical tools to suit the particular needs for in situ or operando gas storage and separation and catalytic studies. This review covers the recent development of using synchrotron X-ray powder diffraction as the primary tool for the study of fundamental interactions with organic molecules with active sites in powder zeolites, as well as some perspectives based on this experimental capability.
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May 2018
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