| 1. |
- Xiao, Kefeng, et al.
(författare)
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Mechanically Improving Ion Diffusion in Layered Conducting Polymers for Compact Energy Storage
- 2024
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Ingår i: ACS Energy Letters. - 2380-8195. ; 9:6, s. 2564-2571
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Tidskriftsartikel (refereegranskat)abstract
- Layered conducting polymers have drawn widespread interest in electrochemical energy systems with capacitive ion storage. However, the semi-infinite ion diffusion through the lengthy path within their lamellar structures restricts the power performance, especially in high mass loading electrodes (>10 mg cm–2). Herein, we improve the ion diffusion in layered conducting polymers by constructing ion-penetrable defects through mechanical modulation of hydrogen bonding, i.e., ball milling. The ball-milled layered conducting polymers endow the fabrication of high mass loading (up to 30 mg cm–2) electrodes for electrochemical capacitors (ECs) with a remarkable areal capacitance of 1.71 F cm–2 and volumetric capacitance of 148.2 F cm–3 at 150 mA cm–2. Asymmetric ECs are further prototyped, delivering a high areal energy of 0.916 mWh cm–2 and a volumetric energy of 28.68 Wh L–1 at 12.5 mW cm–2. These findings represent a critical step forward to the practical application of layered conducting polymers for high-power devices with miniaturized configuration.
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| 2. |
- Chen, Pohua, et al.
(författare)
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Stabilization of Extra-Large-Pore Zeolite by Boron Substitution for the Production of Commercially Applicable Catalysts
- 2022
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 28:63
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Tidskriftsartikel (refereegranskat)abstract
- Stable extra-large-pore zeolites are desirable for industrial purposes due to their ability to accommodate bulky reactants and diffusion through channels. Although there are several extra-large pore zeolites reported, stable ones are rare. Thus, their stabilization is a feasible strategy for industrial applications. Here, an extra-large-pore zeolite EWT with boron substitution is presented, and the resulting zeolite B-RZM-3 increased the thermal stability from 600 °C in its silica form to 850 °C. The crystal structure, determined by combining continuous rotation electron diffraction (cRED) and powder X-ray diffraction (PXRD), shows that B atoms preferentially substitute the interrupted (HO)T(OT)3 (Q3) sites and are partially converted into 3-coordination to relax framework deformation upon heating. After Al-reinsertion post-treatment, Al-B-RZM-3 shows higher ethylbenzene selectivity and ethylene conversion rate per mol acid site than commercial ZSM-5 and Beta zeolite in benzene alkylation reaction. Synthesizing extra-large-pore zeolite in borosilicate form is a potential approach to stabilize interrupted zeolites for commercial applications.
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| 3. |
- Cheung, Ocean, et al.
(författare)
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Nanostructure and pore size control of template-free synthesised mesoporous magnesium carbonate
- 2016
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 6:78, s. 74241-74249
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Tidskriftsartikel (refereegranskat)abstract
- The structure of mesoporous magnesium carbonate (MMC) first presented in 2013 is investigated using a bottom-up approach. MMC is found to be built from the aggregation of nanoparticles of amorphous MgCO3 and MgO with a coating of amorphous MgCO3. The nanoparticles have dimensions of approximately 2-5 nm as observed using transmission electron microscopy and the aggregation of the particles creates the pore structure of MMC. We further show that the average pore diameter of MMC can be controlled by varying the temperature during the powder formation process and demonstrate that altering the pore size opens the possibility to tune the amorphous phase stabilisation properties that MMC exerts on poorly soluble drug compounds. Specifically, we show the loading and release of the antifungal drug itraconazole using MMC as a drug carrier.
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| 4. |
- Cheung, Ocean, et al.
(författare)
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Nanostructure and pore size control of template-free synthesised mesoporous magnesium carbonate
- 2016
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Ingår i: RSC Advances. ; 6:78, s. 74241-74249
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Tidskriftsartikel (refereegranskat)abstract
- The structure of mesoporous magnesium carbonate (MMC) first presented in 2013 is investigated using a bottom-up approach. MMC is found to be built from the aggregation of nanoparticles of amorphous MgCO3 and MgO with a coating of amorphous MgCO3. The nanoparticles have dimensions of approximately 2-5 nm as observed using transmission electron microscopy and the aggregation of the particles creates the pore structure of MMC. We further show that the average pore diameter of MMC can be controlled by varying the temperature during the powder formation process and demonstrate that altering the pore size opens the possibility to tune the amorphous phase stabilisation properties that MMC exerts on poorly soluble drug compounds. Specifically, we show the loading and release of the antifungal drug itraconazole using MMC as a drug carrier.
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| 5. |
- Dai, Heng, et al.
(författare)
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Enhanced Selectivity and Stability of Finned Ferrierite Catalysts in Butene Isomerization
- 2022
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Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 61:8
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Tidskriftsartikel (refereegranskat)abstract
- Designing zeolite catalysts with improved mass transport properties is crucial for restrictive networks of either one- or two-dimensional pore topologies. Here, we demonstrate the synthesis of finned ferrierite (FER), a commercial zeolite with two-dimensional pores, where protrusions on crystal surfaces behave as pseudo nanoparticles. Catalytic tests of 1-butene isomerization reveal a 3-fold enhancement of catalyst lifetime and an increase of 12 % selectivity to isobutene for finned samples compared to corresponding seeds. Electron tomography was used to confirm the identical crystallographic registry of fins and seeds. Time-resolved titration of Bronsted acid sites confirmed the improved mass transport properties of finned ferrierite compared to conventional analogues. These findings highlight the advantages of introducing fins through facile and tunable post-synthesis modification to impart material properties that are otherwise unattainable by conventional synthesis methods.
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| 6. |
- Dai, Heng, et al.
(författare)
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Finned zeolite catalysts
- 2020
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Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-1122 .- 1476-4660. ; 19:10, s. 1074-1080
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Tidskriftsartikel (refereegranskat)abstract
- Nanosized zeolites enable better catalytic performance; however, their synthesis is non-trivial. Here, a simple treatment is presented that enables the growth of nanosized fins on zeolites that act as pseudo-nanoparticles, reducing deactivation rates for methanol-to-hydrocarbon catalysis. There is growing evidence for the advantages of synthesizing nanosized zeolites with markedly reduced internal diffusion limitations for enhanced performances in catalysis and adsorption. Producing zeolite crystals with sizes less than 100 nm, however, is non-trivial, often requires the use of complex organics and typically results in a small product yield. Here we present an alternative, facile approach to enhance the mass-transport properties of zeolites by the epitaxial growth of fin-like protrusions on seed crystals. We validate this generalizable methodology on two common zeolites and confirm that fins are in crystallographic registry with the underlying seeds, and that secondary growth does not impede access to the micropores. Molecular modelling and time-resolved titration experiments of finned zeolites probe internal diffusion and reveal substantial improvements in mass transport, consistent with catalytic tests of a model reaction, which show that these structures behave as pseudo-nanocrystals with sizes commensurate to that of the fin. This approach could be extended to the rational synthesis of other zeolite and aluminosilicate materials.
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| 7. |
- Ge, Meng, 1993-, et al.
(författare)
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Direct Location of Organic Molecules in Framework Materials by Three-Dimensional Electron Diffraction
- 2022
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 144:33, s. 15165-15174
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Tidskriftsartikel (refereegranskat)abstract
- In the study of framework materials, probing interactions between frameworks and organic molecules is one of the most important tasks, which offers us a fundamental understanding of host–guest interactions in gas sorption, separation, catalysis, and framework structure formation. Single-crystal X-ray diffraction (SCXRD) is a conventional method to locate organic species and study such interactions. However, SCXRD demands large crystals whose quality is often vulnerable to, e.g., cracking on the crystals by introducing organic molecules, and this is a major challenge to use SCXRD for structural analysis. With the development of three-dimensional electron diffraction (3D ED), single-crystal structural analysis can be performed on very tiny crystals with sizes on the nanometer scale. Here, we analyze two framework materials, SU-8 and SU-68, with organic molecules inside their inorganic crystal structures. By applying 3D ED, with fast data collection and an ultralow electron dose (0.8–2.6 e– Å–2), we demonstrate for the first time that each nonhydrogen atom from the organic molecules can be ab initio located from structure solution, and they are shown as distinct and well-separated peaks in the difference electrostatic potential maps showing high accuracy and reliability. As a result, two different spatial configurations are identified for the same guest molecule in SU-8. We find that the organic molecules interact with the framework through strong hydrogen bonding, which is the key to immobilizing them at well-defined positions. In addition, we demonstrate that host–guest systems can be studied at room temperature. Providing high accuracy and reliability, we believe that 3D ED can be used as a powerful tool to study host–guest interactions, especially for nanocrystals.
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| 8. |
- Ge, Meng, et al.
(författare)
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On the completeness of three-dimensional electron diffraction data for structural analysis of metal-organic frameworks
- 2021
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Ingår i: Faraday discussions. - 1359-6640 .- 1364-5498. ; 231
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Tidskriftsartikel (refereegranskat)abstract
- Three-dimensional electron diffraction (3DED) has been proven as an effective and accurate method for structure determination of nano-sized crystals. In the past decade, the crystal structures of various new complex metal-organic frameworks (MOFs) have been revealed by 3DED, which has been the key to understand their properties. However, due to the design of transmission electron microscopes (TEMs), one drawback of 3DED experiments is the limited tilt range of goniometers, which often leads to incomplete 3DED data, particularly when the crystal symmetry is low. This drawback can be overcome by high throughput data collection using continuous rotation electron diffraction (cRED), where data from a large number of crystals can be collected and merged. Here, we investigate the effects of improving completeness on structural analysis of MOFs. We use ZIF-EC1, a zeolitic imidazolate framework (ZIF), as an example. ZIF-EC1 crystallizes in a monoclinic system with a plate-like morphology. cRED data of ZIF-EC1 with different completeness and resolution were analyzed. The data completeness increased to 92.0% by merging ten datasets. Although the structures could be solved from individual datasets with a completeness as low as 44.5% and refined to a high precision (better than 0.04 angstrom), we demonstrate that a high data completeness could improve the structural model, especially on the electrostatic potential map. We further discuss the strategy adopted during data merging. We also show that ZIF-EC1 doped with cobalt can act as an efficient electrocatalyst for oxygen reduction reactions.
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| 9. |
- Jaradat, Ahmad, et al.
(författare)
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A High-Rate Li–CO2 Battery Enabled by 2D Medium-Entropy Catalyst
- 2023
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Ingår i: Advanced Functional Materials. - 1616-301X .- 1616-3028. ; 33:21
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Tidskriftsartikel (refereegranskat)abstract
- Lithium-air batteries based on CO2 reactant (Li–CO2) have recently been of interest because it has been found that reversible Li/CO2 electrochemistry is feasible. In this study, a new medium-entropy cathode catalyst, (NbTa)0.5BiS3, that enables the reversible electrochemistry to operate at high rates is presented. This medium entropy cathode catalyst is combined with an ionic liquid-based electrolyte blend to give a Li–CO2 battery that operates at high current density of 5000 mA g−1 and capacity of 5000 mAh g−1 for up to 125 cycles, far exceeding reported values in the literature for this type of battery. The higher rate performance is believed to be due to the greater stability of the multi-element (NbTa)0.5BiS3 catalyst because of its higher entropy compared to previously used catalysts with a smaller number of elements with lower entropies. Evidence for this comes from computational studies giving very low surface energies (high surface stability) for (NbTa)0.5BiS3 and transmission electron microscopystudies showing the structure being retained after cycling. In addition, the calculations indicate that Nb-terminated surface promotes Li–CO2 electrochemistry resulting in Li2CO3 and carbon formation, consistent with the products found in the cell. These results open new direction to design and develop high-performance Li–CO2 batteries.
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| 10. |
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