B18-Core EXAFS
|
Qingqing
Mei
,
Wenyuan
Huang
,
Longfei
Lin
,
Xue
Han
,
Shaojun
Xu
,
Bing
An
,
Svemir
Rudic
,
Rongsheng
Cai
,
Sarah J.
Haigh
,
Buxing
Han
,
Martin
Schroeder
,
Sihai
Yang
Diamond Proposal Number(s):
[36450]
Open Access
Abstract: The synthesis of organic amines via reductive amination of biomass-derived carbonyl compounds is an important target for sustainable chemical industries. The control of selectivity for the formation of primary amines versus secondary amines is challenging, and high temperature and pressures using H2 are required to generate the desired selectivity. Herein, we report the highly selective reductive amination of a broad range of aldehydes and ketones by NH3 and H2 over Rh/MFM-300(Cr) to form primary amines with a selectivity of up to 99% under ambient conditions. Inelastic neutron scattering reveals that the Rh species not only promote the hydrogenation process, but also catalyzes the ammonolysis of the Schiff base intermediate, facilitating the selective synthesis of primary amines. This protocol achieves selective reductive amination at 25 °C and 1 atm, providing an energy-efficient route to a broad spectrum of amines.
|
Nov 2025
|
|
I10-Beamline for Advanced Dichroism - scattering
|
Diamond Proposal Number(s):
[32078]
Open Access
Abstract: This study reports the structural and magnetic properties of Mn-doped Bi2Te3
thin films grown by magnetron sputtering. The films exhibit a ferromagnetic response that depends on the Mn doping concentration, as revealed by X-ray magnetic circular dichroism measurements. At an Mn concentration of ∼6.0%, a magnetic moment of (3.48 ± 0.25) μB
/Mn was determined. Structural analysis indicated the presence of a secondary MnTe𝑥
phase, which complicates the interpretation of the magnetic properties. Additionally, the incorporation of Mn ions within the van der Waals gap and substitutional doping on Bi sites contributes to the observed complex magnetic properties. Intriguingly, a decrease in magnetic moment per Mn was observed with increasing Mn concentration, which is consistent with the formation of the intrinsic magnetic topological insulator MnBi2Te4
.
|
Jan 2025
|
|
B18-Core EXAFS
E01-JEM ARM 200CF
|
Diamond Proposal Number(s):
[2243]
Open Access
Abstract: Mn-doped Co3O4 supported on TiO2 is a well-known Fischer-Tropsch Synthesis (FTS) catalyst. It has been shown that when the Mn doping exceeds 3 wt. %, CO conversion drops and the product selectivity to alcohols and olefins increases dramatically. Here we examine the effect of the preparation method to determine how the proximity of the Mn in the as-prepared catalyst affects FTS performance. Three preparation procedures were examined: preparation of Mn doped Co(Mn)3O4 mixed oxides, surface doping of Co3O4 with Mn3O4 and a physical mixture of the two spinels. Characterisation studies including XRD, XPS and STEM-EDS, of the as-synthesised materials confirmed the successful preparation of spinel materials with crystallite sizes ~ 20 nm. Surface enrichment of Mn on Co3O4 was seen in the surface doped samples but not in the mixed oxide ones. STEM EDS studies revealed that after reduction Mn oxide had migrated to the surface in the mixed oxide samples similar to the surface doped samples. Subsequently, similar CO conversion and product selectivity was observed in both types of sample. However, unlike the surface doped catalysts, the mixed oxide samples did not yield alcohols and olefins, although enhanced CO conversion was observed for the 3 % physical mix. The results highlight the prevalence and importance of the effects of surface Mn doping on the Co speciation which leads to enhanced alcohol/olefin selectivity.
|
Jan 2025
|
|
E02-JEM ARM 300CF
I11-High Resolution Powder Diffraction
|
Eu-Pin
Tien
,
Guanhai
Cao
,
Yinlin
Chen
,
Nick
Clark
,
Evan
Tillotson
,
Duc-The
Ngo
,
Joseph H.
Carter
,
Stephen P.
Thompson
,
Chiu C.
Tang
,
Christopher
Allen
,
Sihai
Yang
,
Martin
Schroeder
,
Sarah J.
Haigh
Diamond Proposal Number(s):
[29225, 30737]
Open Access
Abstract: This work reports the thermal and electron beam stabilities of a series of isostructural metal-organic frameworks (MOFs) of type MFM-300(M), where M = Al, Ga, In, or Cr. MFM-300(Cr) was most electron beam stable, having an unusually high critical electron fluence of 1111 e-·Å-2 while the Group 13 element MOFs were found to be less stable. Within Group 13, MFM-300(Al) had the highest critical electron fluence of 330 e-·Å-2, compared to 189 e-·Å-2 and 147 e-·Å-2 for the Ga and In MOFs respectively. For all four MOFs, electron beam-induced structural degradation was independent of crystal size and was highly anisotropic, with the one-dimensional pore channels being the most stable, although the length and width of the channels decreased during electron beam irradiation. Notably, MFM-300(Cr) was found to retain crystallinity while shrinking up to 10%. Thermal stability was studied using in situ synchrotron X-ray diffraction at elevated temperature which revealed critical temperatures for crystal degradation to be 605, 570, 490 and 480°C for Al, Cr, Ga, and In, respectively. The pore channel diameters contracted by ~0.5% on desorption of solvent species but thermal degradation at higher temperatures was isotropic. The observed electron stabilities were found to scale with the relative inertness of the cations and correlate well to the measured lifetime of the materials when used as photocatalysts.
|
Jul 2024
|
|
B18-Core EXAFS
|
Open Access
Abstract: Background: Biogeochemical processing of metals including the fabrication of novel nanomaterials from metal contaminated waste streams by microbial cells is an area of intense interest in the environmental sciences. Results: Here we focus on the fate of Ce during the microbial reduction of a suite of Ce-bearing ferrihydrites with between 0.2 and 4.2 mol% Ce. Cerium K-edge X-ray absorption near edge structure (XANES) analyses showed that trivalent and tetravalent cerium co-existed, with a higher proportion of tetravalent cerium observed with increasing Ce-bearing of the ferrihydrite. The subsurface metal-reducing bacterium Geobacter sulfurreducens was used to bioreduce Ce-bearing ferrihydrite, and with 0.2 mol% and 0.5 mol% Ce, an Fe(II)-bearing mineral, magnetite (Fe(II)(III)2O4), formed alongside a small amount of goethite (FeOOH). At higher Ce-doping (1.4 mol% and 4.2 mol%) Fe(III) bioreduction was inhibited and goethite dominated the final products. During microbial Fe(III) reduction Ce was not released to solution, suggesting Ce remained associated with the Fe minerals during redox cycling, even at high Ce loadings. In addition, Fe L2,3 X-ray magnetic circular dichroism (XMCD) analyses suggested that Ce partially incorporated into the Fe(III) crystallographic sites in the magnetite. The use of Ce-bearing biomagnetite prepared in this study was tested for hydrogen fuel cell catalyst applications. Platinum/carbon black electrodes were fabricated, containing 10% biomagnetite with 0.2 mol% Ce in the catalyst. The addition of bioreduced Ce-magnetite improved the electrode durability when compared to a normal Pt/CB catalyst. Conclusion: Different concentrations of Ce can inhibit the bioreduction of Fe(III) minerals, resulting in the formation of different bioreduction products. Bioprocessing of Fe-minerals to form Ce-containing magnetite (potentially from waste sources) offers a sustainable route to the production of fuel cell catalysts with improved performance.
|
Apr 2024
|
|
E02-JEM ARM 300CF
|
S.
Carter-Searjeant
,
S. M.
Fairclough
,
S. J.
Haigh
,
Y.
Zou
,
R. J.
Curry
,
P. N.
Taylor
,
C.
Huang
,
R.
Fleck
,
P.
Machado
,
A. I.
Kirkland
,
M. A.
Green
Diamond Proposal Number(s):
[16892, 17837]
Open Access
Abstract: Colloidal semiconductor quantum dots are a well-established technology, with numerous materials available either commercially or through the vast body of literature. The prevalent materials are cadmium-based and are unlikely to find general acceptance in most applications. While the III–V family of materials is a likely substitute, issues remain about its long-term suitability, and other earth-abundant materials are being explored. In this report, we highlight a nanoscale half-Heusler semiconductor, LiZnN, composed of readily available elements as a potential alternative system to luminescent II–VI and III–V nanoparticle quantum dots.
|
Jun 2023
|
|
B18-Core EXAFS
I22-Small angle scattering & Diffraction
|
Jingyu
Feng
,
Rongsheng
Cai
,
Emanuele
Magliocca
,
Hui
Luo
,
Luke
Higgins
,
Giulio L. Fumagalli
Romario
,
Xiaoqiang
Liang
,
Angus
Pedersen
,
Zhen
Xu
,
Zhenyu
Guo
,
Arun
Periasamy
,
Dan
Brett
,
Thomas S.
Miller
,
Sarah J.
Haigh
,
Bhoopesh
Mishra
,
Maria-Magdalena
Titirici
Diamond Proposal Number(s):
[26201, 27900]
Open Access
Abstract: Atomically dispersed transition metal-nitrogen-carbon catalysts are emerging as low-cost electrocatalysts for the oxygen reduction reaction in fuel cells. However, a cost-effective and scalable synthesis strategy for these catalysts is still required, as well as a greater understanding of their mechanisms. Herein, iron, nitrogen co-doped carbon spheres (Fe@NCS) have been prepared via hydrothermal carbonization and high-temperature post carbonization. It is determined that FeN4 is the main form of iron existing in the obtained Fe@NCS. Two different precursors containing Fe2+ and Fe3+ are compared. Both chemical and structural differences have been observed in catalysts starting from Fe2+ and Fe3+ precursors. Fe2+@NCS-A (starting with Fe2+ precursor) shows better catalytic activity for the oxygen reduction reaction. This catalyst is studied in an anion exchange membrane fuel cell. The high open-circuit voltage demonstrates the potential approach for developing high-performance, low-cost fuel cell catalysts.
|
Aug 2021
|
|
|
|
Gerard M.
Leteba
,
Yi-Chi
Wang
,
Thomas J. A.
Slater
,
Rongsheng
Cai
,
Conor
Byrne
,
Christopher P.
Race
,
David R. G.
Mitchell
,
Pieter B. J.
Levecque
,
Neil P.
Young
,
Stuart M.
Holmes
,
Alex
Walton
,
Angus I.
Kirkland
,
Sarah J.
Haigh
,
Candace I.
Lang
Open Access
Abstract: We report a rapid solution-phase strategy to synthesize alloyed PtNi nanoparticles which demonstrate outstanding functionality for the oxygen reduction reaction (ORR). This one-pot coreduction colloidal synthesis results in a monodisperse population of single-crystal nanoparticles of rhombic dodecahedral morphology with Pt-enriched edges and compositions close to Pt1Ni2. We use nanoscale 3D compositional analysis to reveal for the first time that oleylamine (OAm)-aging of the rhombic dodecahedral Pt1Ni2 particles results in Ni leaching from surface facets, producing aged particles with concave faceting, an exceptionally high surface area, and a composition of Pt2Ni1. We show that the modified atomic nanostructures catalytically outperform the original PtNi rhombic dodecahedral particles by more than two-fold and also yield improved cycling durability. Their functionality for the ORR far exceeds commercially available Pt/C nanoparticle electrocatalysts, both in terms of mass-specific activities (up to a 25-fold increase) and intrinsic area-specific activities (up to a 27-fold increase).
|
Apr 2021
|
|
I06-Nanoscience (XPEEM)
|
D.
Pesquera
,
E.
Khestanova
,
M.
Ghidini
,
S.
Zhang
,
A. P.
Rooney
,
F.
Maccherozzi
,
P.
Riego
,
S.
Farokhipoor
,
J.
Kim
,
X.
Moya
,
M. E.
Vickers
,
N. A.
Stelmashenko
,
S. J.
Haigh
,
S. S.
Dhesi
,
N. D.
Mathur
Diamond Proposal Number(s):
[14745]
Open Access
Abstract: Epitaxial films may be released from growth substrates and transferred to structurally and chemically incompatible substrates, but epitaxial films of transition metal perovskite oxides have not been transferred to electroactive substrates for voltage control of their myriad functional properties. Here we demonstrate good strain transmission at the incoherent interface between a strain-released film of epitaxially grown ferromagnetic La0.7Sr0.3MnO3 and an electroactive substrate of ferroelectric 0.68Pb(Mg1/3Nb2/3)O3-0.32PbTiO3 in a different crystallographic orientation. Our strain-mediated magnetoelectric coupling compares well with respect to epitaxial heterostructures, where the epitaxy responsible for strong coupling can degrade film magnetization via strain and dislocations. Moreover, the electrical switching of magnetic anisotropy is repeatable and non-volatile. High-resolution magnetic vector maps reveal that micromagnetic behaviour is governed by electrically controlled strain and cracks in the film. Our demonstration should inspire others to control the physical/chemical properties in strain-released epitaxial oxide films by using electroactive substrates to impart strain via non-epitaxial interfaces.
|
Jun 2020
|
|
E02-JEM ARM 300CF
|
Astrid
Weston
,
Yichao
Zou
,
Vladimir
Enaldiev
,
Alex
Summerfield
,
Nicholas
Clark
,
Viktor
Zólyomi
,
Abigail
Graham
,
Celal
Yelgel
,
Samuel
Magorrian
,
Mingwei
Zhou
,
Johanna
Zultak
,
David
Hopkinson
,
Alexei
Barinov
,
Thomas H.
Bointon
,
Andrey
Kretinin
,
Neil R.
Wilson
,
Peter H.
Beton
,
Vladimir I.
Fal’ko
,
Sarah J.
Haigh
,
Roman
Gorbachev
Diamond Proposal Number(s):
[19315, 21597]
Abstract: Van der Waals heterostructures form a unique class of layered artificial solids in which physical properties can be manipulated through controlled composition, order and relative rotation of adjacent atomic planes. Here we use atomic-resolution transmission electron microscopy to reveal the lattice reconstruction in twisted bilayers of the transition metal dichalcogenides, MoS2 and WS2. For twisted 3R bilayers, a tessellated pattern of mirror-reflected triangular 3R domains emerges, separated by a network of partial dislocations for twist angles θ < 2°. The electronic properties of these 3R domains, featuring layer-polarized conduction-band states caused by lack of both inversion and mirror symmetry, appear to be qualitatively different from those of 2H transition metal dichalcogenides. For twisted 2H bilayers, stable 2H domains dominate, with nuclei of a second metastable phase. This appears as a kagome-like pattern at θ ≈ 2°, transitioning at θ → 0 to a hexagonal array of screw dislocations separating large-area 2H domains. Tunnelling measurements show that such reconstruction creates strong piezoelectric textures, opening a new avenue for engineering of 2D material properties.
|
May 2020
|
|
