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40 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2, 3, 4 [Next/Last]

Instruments / Technical Area	Publication Details	Published
I11-High Resolution Powder Diffraction	In situ phase transformation on nickel-based selenides for enhanced hydrogen evolution reaction in alkaline medium Lingling Zhai , Tsz Woon Benedict Lo , Zheng-long Xu , Jonathan Potter , Jiaying Mo , Xuyun Guo , Chiu Chung Tang , Shik Chi Edman Tsang , Shu Ping Lau Acs Energy Letters DOI: 10.1021/acsenergylett.0c01385 Diamond Proposal Number(s): [23230] Show Abstract ▼ Abstract: Identification of the active species in electrocatalysts toward hydrogen evolution reaction (HER) is of great significance for the development of the catalytic industry; however, it is still the subject of considerable controversy. Herein, we applied operando synchrotron X-ray powder diffraction (SXRD) in the NiSe2 electrocatalyst system, and an in situ phase transformation from cubic NiSe2 to hexagonal NiSe was revealed. The NiSe phase showed an enhanced catalytic activity. Operando Raman spectroscopy verified the decomposition of NiSe2 during HER. Theoretical calculations suggested that the charge transfers from the Se site to Ni site during this evolution process, leading to an increased conductivity and a shifting up of d-band center, which is attributed to the enhanced activity. The generated NiSe phase acts as the “real” active species. Our work unravels the underlying phase transition of the electrocatalyst on reductive conditions in alkaline medium and highlights the significance of identifying the intrinsic active sites under realistic reaction conditions.	Jul 2020
B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS	Methanol synthesis at a wide range of H2/CO2 ratios over Rh‐In bimetallic catalyst Molly Meng-jung Li , Hanbo Zou , Jianwei Zheng , Tai-sing Wu , Ting-shan Chan , Yun-liang Soo , Xin-ping Wu , Xueqing Gong , Tianyi Chen , Kanak Roy , Georg Held , Edman Shik Chi Tsang Angewandte Chemie International Edition DOI: 10.1002/anie.202000841 Show Abstract ▼ Abstract: Recent years have seen an increasing interest in capturing hydrogen generated from renewables with CO 2 to produce methanol. However, renewable hydrogen production is currently expensive and in limited quantity as compared to CO 2 . Excess CO 2 and limited H 2 in the feedstock gas mixture is not favourable for the CO 2 hydrogenation to methanol reaction, which causes low activity and poor methanol selectivity. Here we report a new class of Rh‐In catalysts with optimal adsorption property to the intermediates of methanol production. The Rh‐In catalyst can effectively catalyse methanol synthesis but inhibit reverse water‐gas shift reaction under H 2 ‐deficient gas flow and shows the best competitive methanol productivity under industrially applicable conditions in comparison with the literature reported values. This work demonstrates a strong potential of Rh‐In bimetallic composition, from which a convenient methanol synthesis based on flexible feedstock compositions (e.g. H 2 /CO 2 from biomass derivatives) with lower energy cost can be established.	May 2020
I11-High Resolution Powder Diffraction	Evaluation of Brønsted and Lewis acid sites in H-ZSM-5 and H-USY with or without metal modification using probe molecule-synchrotron X-ray powder diffraction Benedict T. W. Lo , Wei-che Lin , Molly Meng Jung Li , Sarah Day , Chiu Tang , Shik Chi Edman Tsang Applied Catalysis A: General 596 DOI: 10.1016/j.apcata.2020.117528 Show Abstract ▼ Abstract: The adsorbate interactions of furans as probe molecules in H-ZSM-5 and H-USY with and without metal ion modification have been revealed by synchrotron X-ray powder diffraction (SXRD). The Rietveld refinements give both qualitatively and quantitatively the spatial arrangements and adsorption geometries of furan and 2,5-dimethylfuran (DMF) on the Brønsted acid sites (BAS) and metal Lewis acid sites (LAS). The bonding information between the adsorbate-framework can also be correlated with thermogravimetric findings. The use of probe molecule-SXRD can be used as a new characterisation tool which can spatially interrogate the acidity of crystalline porous catalysts, leading to molecular engineering of new catalytic systems.	Apr 2020
B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS	Removal of hydrogen poisoning by electrostatically polar MgO support for low pressure NH3 synthesis at high rate over Ru catalyst Simson Wu , Yung-kang Peng , Tianyi Chen , Jiaying Mo , Alex Large , Ian Mcpherson , Hung-lung Chou , Ian Wilkinson , Federica Venturini , David Grinter , Pilar Ferrer Escorihuela , Georg Held , Shik Chi Edman Tsang Acs Catalysis DOI: 10.1021/acscatal.0c00954 Show Abstract ▼ Abstract: The increasing availability of low-cost and low pressure, renewable H2 from wind and solar means has triggered tremendous interest in developing low pressure ammonia synthesis with N2 as energy carrier as well as green fertilizer. As such Cs-promoted Ru/MgO catalysts used in Kellogg process show superiority to Fe-based catalysts at milder conditions, however, as known, the surface poisoning of Ru sites by competitive strong H2 dissociative adsorption limits the overall rate. It is demonstrated for the first time that the use of simple polar MgO(111) to replace non-polar MgO as support can significantly alleviate the hydrogen poisoning and facilitate an unprecedented ammonia production rate by its high intrinsic proton capture ability.	Apr 2020
I11-High Resolution Powder Diffraction	Differential adsorption of L- and D-lysine on achiral MFI zeolites as determined by synchrotron X-ray powder diffraction and thermogravimetric analysis Tianxiang Chen , Bolong Huang , Sarah Day , Chiu Chung Tang , Shik Chi Edman Tsang , Kwok-yin Wong , Tsz Woon Benedict Lo Angewandte Chemie International Edition DOI: 10.1002/anie.201909352 Diamond Proposal Number(s): [23230] Show Abstract ▼ Abstract: We report the first crystallographic observation of stereospecific bindings of L‐ and D‐lysine in achiral MFI zeolites. The MFI structure has offered inherent geometric and internal confinement effects for the enantiomeric difference in L‐ and D‐lysine adsorption. Notable difference over the sorption properties has been observed by circular dichroism (CD) spectroscopy and thermogravimetric analysis (TGA). Distinct L‐ and D‐lysine adsorption behaviours on the H‐ZSM‐5 framework have been revealed by the Rietveld refinement of high‐resolution synchrotron X‐ray powder diffraction (SXRD) data and the density functional theory (DFT) calculation. Despite only demonstrated in L‐ and D‐lysine over MFI zeolites, the differential adsorption study sheds light towards the rational engineering of molecular interactions(s) with achiral microporous materials for chiral separation purposes.	Nov 2019
I11-High Resolution Powder Diffraction I15-1-X-ray Pair Distribution Function (XPDF)	Interstitial boron atoms in palladium lattice of industrial type of nano-catalyst: Properties and structural modifications 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 Journal Of The American Chemical Society DOI: 10.1021/jacs.9b06120 Diamond Proposal Number(s): [15452] Show Abstract ▼ 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.	Nov 2019
E01-JEM ARM 200CF	Molecular nitrogen promotes catalytic hydrodeoxygenation Haohong Duan , Jin-cheng Liu , Ming Xu , Yufei Zhao , Xue-lu Ma , Juncai Dong , Xusheng Zheng , Jianwei Zheng , Christopher Allen , Mohsen Danaie , Yung-kang Peng , Titipong Issariyakul , Dongliang Chen , Angus Kirkland , Jean-charles Buffet , Jun Li , Shik Chi Edman Tsang , Dermot O'hare Nature Catalysis 345 DOI: 10.1038/s41929-019-0368-6 Diamond Proposal Number(s): [16969, 17397] Show Abstract ▼ Abstract: Although molecular dinitrogen (N2) is widely used as a carrier or inert gas for many catalytic reactions, it is rarely considered as a catalytic promoter. Here, we report that N2 could be used to reduce the activation energy for catalytic hydrodeoxygenation over ruthenium-based catalysts. Specifically, we report a 4.3-fold activity increase in the catalytic hydrodeoxygenation of p-cresol to toluene over a titanium oxide supported ruthenium catalyst (Ru/TiO2) by simply introducing 6 bar N2 under batch conditions at 160 °C and 1 bar hydrogen. Detailed investigations indicate that N2 can be adsorbed and activated on the metallic ruthenium surface to form hydrogenated nitrogen species, which offer protic hydrogen to lower the activation energy of direct carbonaromatic–oxygen bond scission and the hydrogenation of hydroxy groups. Thus, by employing different ruthenium catalysts, including Ru/TiO2, Ru/Al2O3, Ru/ZrO2 and Ru/C, we demonstrate that N2 promotion of hydrodeoxygenation can be regarded as a general strategy.	Oct 2019
I11-High Resolution Powder Diffraction	Selective production of diethyl maleate via oxidative cleavage of lignin aromatic unit 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 Chem DOI: 10.1016/j.chempr.2019.05.021 Show Abstract ▼ 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.	Jun 2019
E01-JEM ARM 200CF	Ceria nanocrystals supporting Pd for formic acid electrocatalytic oxidation: prominent polar surface metal support interactions 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 Acs Catalysis DOI: 10.1021/acscatal.9b00421 Show Abstract ▼ 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.	Apr 2019
I11-High Resolution Powder Diffraction	Structural dynamics of a metal–organic framework induced by CO2 migration in its non-uniform porous structure Pu Zhao , Hong Fang , Sanghamitra Mukhopadhyay , Aurelia Li , Svemir Rudic , Ian J. Mcpherson , Chiu C. Tang , David Fairen-jimenez , Edman Tsang , Simon A. T. Redfern Nature Communications 10 DOI: 10.1038/s41467-019-08939-y Open Access Show Abstract ▼ Abstract: Stimuli-responsive behaviors of flexible metal–organic frameworks (MOFs) make these materials promising in a wide variety of applications such as gas separation, drug delivery, and molecular sensing. Considerable efforts have been made over the last decade to understand the structural changes of flexible MOFs in response to external stimuli. Uniform pore deformation has been used as the general description. However, recent advances in synthesizing MOFs with non-uniform porous structures, i.e. with multiple types of pores which vary in size, shape, and environment, challenge the adequacy of this description. Here, we demonstrate that the CO2-adsorption-stimulated structural change of a flexible MOF, ZIF-7, is induced by CO2 migration in its non-uniform porous structure rather than by the proactive opening of one type of its guest-hosting pores. Structural dynamics induced by guest migration in non-uniform porous structures is rare among the enormous number of MOFs discovered and detailed characterization is very limited in the literature. The concept presented in this work provides new insights into MOF flexibility.	Mar 2019

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