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153 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2, 3, 4, 5, 6, 7, 8 [Next/Last]

Instruments / Technical Area	Publication Details	Published
E01-JEM ARM 200CF	Controlling nanocluster growth through nanoconfinement: the effect of the number and nature of metal-organic framework functionalities James King , Zhipeng Lin , Federica Zanca , Hui Luo , Linda Zhang , Patrick Cullen , Mohsen Danaie , Michael Hirscher , Simone Meloni , Alin Elena , Petra A. Szilagyi Physical Chemistry Chemical Physics DOI: 10.1039/D4CP02422B Diamond Proposal Number(s): [25791] Open Access Show Abstract ▼ Abstract: Controlled nanocluster growth via nanoconfinement is an attractive approach as it allows for geometry control and potential surface-chemistry modification simultaneously. However, it is still not a straight-forward method and much of its success depends on the nature and possibly concentration of functionalities on the cavity walls that surround the clusters. To independently probe the effect of the nature and number of functional groups on the controlled Pd nanocluster growth within the pores of the metal-organic frameworks, Pd-laden UiO-66 analogues with mono- and bi-functionalised linkers of amino and methyl groups were successfully prepared and studied in a combined experimental-computational approach. The nature of the functional groups determines the strength of host-guest interactions, while the number of functional groups affects the extent of Pd loading. The interplay of these two effects means that for a successful Pd embedding, mono-functionalised host matrices are more favourable. Interestingly, in the context of the present and previous research, we find that host frameworks with functional groups displaying higher Lewis basicity are more successful at controlled Pd NC growth via nanoconfinement in MOFs.	Sep 2024
B18-Core EXAFS E02-JEM ARM 300CF	Design and understanding of adaptive hydrogenation catalysts triggered by the H2/CO2-formic acid equilibrium Yuyan Zhang , Natalia Levin , Liqun Kang , Felix Mueller , Mirijam Zobel , Serena Debeer , Walter Leitner , Alexis Bordet Journal Of The American Chemical Society 3 DOI: 10.1021/jacs.4c06765 Diamond Proposal Number(s): [33118, 35401] Open Access Show Abstract ▼ Abstract: An adaptive catalytic system for selective hydrogenation was developed exploiting the H2 + CO2 ⇔ HCOOH equilibrium for reversible, rapid, and robust on/off switch of the ketone hydrogenation activity of ruthenium nanoparticles (Ru NPs). The catalyst design was based on mechanistic studies and DFT calculations demonstrating that adsorption of formic acid to Ru NPs on silica results in surface formate species that prevent C═O hydrogenation. Ru NPs were immobilized on readily accessible silica supports modified with guanidinium-based ionic liquid phases (Ru@SILPGB) to generate in situ sufficient amounts of HCOOH when CO2 was introduced into the H2 feed gas for switching off ketone hydrogenation while maintaining the activity for hydrogenation of olefinic and aromatic C═C bonds. Upon shutting down the CO2 supply, the C═O hydrogenation activity was restored in real time due to the rapid decarboxylation of the surface formate species without the need for any changes in the reaction conditions. Thus, the newly developed Ru@SILPGB catalysts allow controlled and alternating production of either saturated alcohols or ketones from unsaturated substrates depending on the use of H2 or H2/CO2 as feed gas. The major prerequisite for design of adaptive catalytic systems based on CO2 as trigger is the ability to shift the H2 + CO2 ⇔ HCOOH equilibrium sufficiently to exploit competing adsorption of surface formate and targeted functional groups. Thus, the concept can be expected to be more generally applicable beyond ruthenium as the active metal, paving the way for next-generation adaptive catalytic systems in hydrogenation reactions more broadly.	Sep 2024
E02-JEM ARM 300CF	Benign methylformamidinium byproduct induced by cation heterogeneity inhibits local formation of δ-phase perovskites Jihoo Lim , Jaehui Kim , Josh Davies-Jones , Mohsen Danaie , Eunyoung Choi , Hongjae Shim , Liang Chen , Jincheol Kim , Judy S. Kim , Philip R. Davies , Jan Seidel , Martin Green , Samuel D. Stranks , Sang Il Seok , Jae Yun Energy & Environmental Science DOI: 10.1039/D4EE03058C Diamond Proposal Number(s): [34931] Show Abstract ▼ Abstract: Efforts to enhance the efficiency and stability of formamidinium lead triiodide (FAPbI3) perovskite solar cells (PSCs) have primarily focused on employing methylammonium chloride (MACl) as an effective additive. MACl significantly improves the crystallinity and lowers the δ-to-α phase transition temperature of FAPbI3, thereby contributing to the remarkable efficiency of these solar cells. However, upon evaporation with deprotonation of MACl during annealing, the highly reactive methylamine leads to the formation of N-methylformamidinium (MFA+) cations. Despite their potential for significant influence on the properties of FAPbI3 perovskites, the chemical and optoelectronic characteristics of MFA+ in FAPbI3 remain poorly understood. This study investigates the unexplored role of MFA+ in FAPbI3 perovskite with MACl incorporation through advanced nanoscale characterization techniques, including photo-induced force microscopy (PiFM), four-dimensional scanning transmission electron microscopy, and wavelength-dependent Kelvin probe force microscopy (KPFM). We reveal that MACl induces compositional heterogeneities, particularly formamidinium (FA+) and MFA+ cation inhomogeneities. Surprisingly, MACl selectively promotes the formation of MFAPbI3 at grain boundaries (GBs) and as clusters near GBs. Additionally, we confirm that MFAPbI3 is a wide bandgap, and charge carriers are effectively separated at GBs and clusters enriched with MFAPbI3. This is particularly interesting because MFAPbI3, despite its crystal structural similarity to yellow phase δ-FAPbI3, displays a high surface photovoltage, and does not deteriorate the solar cell performance. This study not only provides insights into the byproduct formation of MFA+ induced by local cation heterogeneity after employing MACl, but also guides a crucial perspective for optimizing formamidinium-based PSC design and performance.	Aug 2024
E01-JEM ARM 200CF	Visualization of tetrahedral Li in the alkali layers of Li-rich layered metal oxides Weixin Song , Miguel A. Pérez-Osorio , Jun Chen , Zhiyuan Ding , John-Joseph Marie , Mikkel Juelsholt , Robert A. House , Peter G. Bruce , Peter D. Nellist Journal Of The American Chemical Society DOI: 10.1021/jacs.4c05556 Diamond Proposal Number(s): [32135] Open Access Show Abstract ▼ Abstract: Understanding Li+ ion diffusion pathways in Li-rich layered transition metal (TM) oxides is crucial for understanding the sluggish kinetics in anionic O2– redox. Although Li diffusion within the alkali layers undergoes a low-barrier octahedral–tetrahedral–octahedral pathway, it is less clear how Li diffuses in and out of the TM layers, particularly given the complex structural rearrangements that take place during the oxidation of O2–. Here, we develop simultaneous electron ptychography and annular dark field imaging methods to unlock the Li migration pathways in Li1.2Ni0.13Mn0.54Co0.13O2 associated with structural changes in the charge–discharge cycle. At the end of TM oxidation and before the high-voltage O oxidation plateau, we show that the Li migrating out of the TM layers occupies the alkali-layer tetrahedral sites on opposite sides of the TM layers, forming Li–Li dumbbell configurations, consistent with the density functional theory calculations. Also occurring are the TM migration and phase transition from O3 to O1 stacking, leading to unstable tetrahedral Li and the absence of Li contrast in imaging. Upon further Li deintercalation to 4.8 V, most of the tetrahedral Li are removed. After discharging to 2 V, we did not identify the reformation of tetrahedral Li but observed permanently migrated TMs at the alkali-layer sites, disfavoring the Li occupying the tetrahedral sites for diffusion. Our findings suggest a landscape of Li diffusion pathways in Li-rich layered oxides and strategies for minimizing the disruption of Li diffusion.	Aug 2024
B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS E01-JEM ARM 200CF I09-Surface and Interface Structural Analysis I20-EDE-Energy Dispersive EXAFS (EDE) I20-Scanning-X-ray spectroscopy (XAS/XES)	Subsurface single-atom catalyst enabled by mechanochemical synthesis for oxidation chemistry Xuze Guan , Rong Han , Hiroyuki Asakura , Bolun Wang , Lu Chen , Jay Hon Cheung Yan , Shaoliang Guan , Luke Keenan , Shusaku Hayama , Matthijs A. Van Spronsen , Georg Held , Jie Zhang , Hao Gu , Yifei Ren , Lun Zhang , Zhangyi Yao , Yujiang Zhu , Anna Regoutz , Tsunehiro Tanaka , Yuzheng Guo , Feng Ryan Wang Angewandte Chemie International Edition DOI: 10.1002/anie.202410457 Diamond Proposal Number(s): [23759, 24450, 29092, 31852] Open Access Show Abstract ▼ Abstract: Single-atom catalysts have garnered significant attention due to their exceptional atom utilization and unique properties. However, the practical application of these catalysts is often impeded by challenges such as sintering-induced instability and poisoning of isolated atoms due to strong gas adsorption. In this study, we employed the mechanochemical method to insert single Cu atoms into the subsurface of Fe2O3 support. By manipulating the location of single atoms at the surface or subsurface, catalysts with distinct adsorption properties and reaction mechanisms can be achieved. It was observed that the subsurface Cu single atoms in Fe2O3 remained isolated under both oxidation and reduction environments, whereas surface Cu single atoms on Fe2O3 experienced sintering under reduction conditions. The unique properties of these subsurface single-atom catalysts call for innovations and new understandings in catalyst design.	Jul 2024
E01-JEM ARM 200CF	Cation ordering in low-temperature niobium-rich NbWO bronzes: New anodes for high-rate Li-ion batteries Supreeth Nagendran , Amoghavarsha Mahadevegowda , Sundeep Vema , Mohsen Danaie , Weixin Song , Bo Wen , Caterina Ducati , Clare P. Grey Matter 559 DOI: 10.1016/j.matt.2024.06.023 Diamond Proposal Number(s): [32597, 28816] Show Abstract ▼ Abstract: Niobium tungsten oxides are gaining attention as anodes for lithium-ion batteries due to their high volumetric energy storage densities obtained at high cycling rates. Two new niobium tungsten bronze structures, NbWO5.5 and β-Nb2WO8, were prepared with microwave-assisted solution-based methods at 800°C. These adopt a simple tetragonal tungsten bronze (TTB) and a √2 × √2 TTB superstructure, respectively. Nb3WO10.5 with a structure closely related to β-Nb2WO8 was formed at higher Nb:W ratios. Nb:W ≥ 4 compositions result in two-phase behavior forming Nb2O5 and Nb3WO10.5, while W-rich bronzes (Nb:W < 1) exhibited local domains of WO3 within the NbWO5.5 lattice. Diffraction and electron microscopy analysis revealed cation ordering in the bronzes at different length scales. The microwave synthesis method produced microporous spheres, with the high-Nb-content phases showing promising high-rate capabilities and long cycle lives, making them suitable for energy-storage applications. The microwave-assisted solution method holds potential for synthesizing complex oxide materials across diverse applications.	Jul 2024
E02-JEM ARM 300CF	Quantitative electron microscopy of zeolites using aberration corrected (S)TEM and machine learning Tahmid Choudhury , Chen Huang , Aakash Varambhia , Alessandro Turrina , Mervyn Shannon , Dogan Ozkaya , Angus I. Kirkland Microscopy & Microanalysis 2024 DOI: 10.1093/mam/ozae044.179 Show Abstract ▼ Abstract: We have developed a semantic segmentation neural network, ZeoSegNN, that can be used to identify intergrowth defects from (S)TEM images of AEI/CHA and MFI/MEL structures, using augmented learning.	Jul 2024
E01-JEM ARM 200CF	Thermally stable high-loading single Cu sites on ZSM-5 for selective catalytic oxidation of NH3 Lu Chen , Xuze Guan , Xinbang Wu , Hiroyuki Asakura , David G. Hopkinson , Christopher Allen , June Callison , Paul J. Dyson , Feng Ryan Wang Proceedings Of The National Academy Of Sciences 121 DOI: 10.1073/pnas.2404830121 Diamond Proposal Number(s): [33314] Open Access Show Abstract ▼ Abstract: Rigorous comparisons between single site- and nanoparticle (NP)-dispersed catalysts featuring the same composition, in terms of activity, selectivity, and reaction mechanism, are limited. This limitation is partly due to the tendency of single metal atoms to sinter into aggregated NPs at high loadings and elevated temperatures, driven by a decrease in metal surface free energy. Here, we have developed a unique two-step method for the synthesis of single Cu sites on ZSM-5 (termed CuS/ZSM-5) with high thermal stability. The atomic-level dispersion of single Cu sites was confirmed through scanning transmission electron microscopy, X-ray absorption fine structure (XAFS), and electron paramagnetic resonance spectroscopy. The CuS/ZSM-5 catalyst was compared to a CuO NP-based catalyst (termed CuN/ZSM-5) in the oxidation of NH3 to N2, with the former exhibiting superior activity and selectivity. Furthermore, operando XAFS and diffuse reflectance infrared Fourier transform spectroscopy studies were conducted to simultaneously assess the fate of the Cu and the surface adsorbates, providing a comprehensive understanding of the mechanism of the two catalysts. The study shows that the facile redox behavior exhibited by single Cu sites correlates with the enhanced activity observed for the CuS/ZSM-5 catalyst.	Jul 2024
E02-JEM ARM 300CF	Combining scanning nanobeam electron diffraction with 3D electron diffraction to investigate crystal defects H. W. Leung , R. C. B. Copley , J. E. M. Laulainen , Duncan N. Johnstone , P. A. Midgley Microscopy & Microanalysis 2024 DOI: 10.1093/mam/ozae044.901 Diamond Proposal Number(s): [33068] Show Abstract ▼ Abstract: In conclusion, this work demonstrates the powerful nature of SED, combined with 3D-ED, to explore sub-crystal nanostructures and defects in beam-sensitive soft materials.	Jul 2024
E02-JEM ARM 300CF I11-High Resolution Powder Diffraction	Electron beam and thermal stabilities of MFM-300(M) metal-organic frameworks 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 Journal Of Materials Chemistry A DOI: 10.1039/D4TA03302G Diamond Proposal Number(s): [29225, 30737] Open Access Show Abstract ▼ 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

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