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Results for “synthesis (scalable processing)”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Open‐Pore Two‐Dimensional MFI Zeolite Nanosheets for the Fabrication of Hydrocarbon‐Isomer‐Selective Membranes on Porous Polymer Supports

Abstract Two‐dimensional zeolite nanosheets that do not contain any organic structure‐directing agents were prepared from a multilamellar MFI (ML‐MFI) zeolite. ML‐MFI was first exfoliated by melt compounding and then detemplated by treatment with a mixture of H 2 SO 4 and H 2 O 2 (piranha solution). The obtained OSDA‐free MFI nanosheets disperse well in water and can be used for coating applications. Deposits made on porous polybenzimidazole (PBI) supports by simple filtration of these suspensions exhibit an n ‐butane/isobutane selectivity of 5.4, with an n ‐butane permeance of 3.5×10 −7 mol m −2 s −1 Pa −1 (ca. 1000 GPU).

Zhang, Han↗
DOE OSTI2017

para -Xylene Ultra-selective Zeolite MFI Membranes Fabricated from Nanosheet Monolayers at the Air-Water Interface

The control of membrane morphology and microstructure is crucial to improve the separation performance of molecular-sieve membranes. This can be enabled by making thin, dense, and uniform seed-crystal coatings, which are then intergrown into continuous membranes. Herein, we show a novel and simple floating particle coating method can give closely packed monolayers of zeolite nanosheets on nonporous or porous supports. The zeolite nanosheet monolayer is formed at the air–water interface in a conical Teflon trough. As the water in the trough is drained, the monolayer is deposited on a support placed below. Membranes prepared by gel-free secondary growth of the nanosheets deposited by this method show unprecedented ultra-selective performance for separation of para- from ortho-xylene (separation factor >10,000).

36 MATERIALS SCIENCE↗
DOE OSTI2019

All-Polymer Solar Cells: Recent Progress, Challenges, and Prospects

For over two decades bulk-heterojunction polymer solar cell (BHJ-PSC) research was dominated by donor:acceptor BHJ blends based on polymer donors and fullerene molecular acceptors. This situation has changed recently, with non-fullerene PSCs developing very rapidly. The power conversion efficiencies of non-fullerene PSCs have now reached over 15 %, which is far above the most efficient fullerene-based PSCs. Among the various non-fullerene PSCs, all-polymer solar cells (APSCs) based on polymer donor-polymer acceptor BHJs have attracted growing attention, due to the following attractions: 1) large and tunable light absorption of the polymer donor/polymer acceptor pair; 2) robustness of the BHJ film morphology; 3) compatibility with large scale/large area manufacturing; 4) long-term stability of the cell to external environmental and mechanical stresses. This Minireview highlights the opportunities offered by APSCs, selected polymer families suitable for these devices with optimization to enhance the performance further, and discusses the challenges facing APSC development for commercial applications.

bio-inspired↗
DOE OSTI2019

In Operando Visualization of the Electrochemical Formation of Liquid Polybromide Microdroplets

Zinc–bromine flow batteries are promising for stationary energy storage, and bromine-complexing agents have been used to form phase-separated liquid polybromide products. However, an understanding of the dynamics of polybromide nucleation is limited due to the beam sensitivity and complexity of polybromides. Here we report an in operando platform composed of dark-field light microscopy and a transparent electrochemical cell to reveal the dynamics of polybromide formation in their native environment. Using our platform, we confirm and reveal the liquid nature, chemical composition, pinning effect (strong interaction with Pt), residual effect (residual charge products on the surface), self-discharging, and over-oxidation of the polybromide products. Overall, the results provide insights into the role of complexing agents and guide the future design of zinc–bromine flow batteries. Furthermore, our in operando platform can potentially be used to study sensitive species and phases in other electrochemical reactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

ZIF-8 Membrane Separation Performance Tuning by Vapor Phase Ligand Treatment

Vapor phase ligand treatment (VPLT) of 2-aminobenzimidazole (2abIm) for 2-methylimidazole (2mIm) in ZIF-8 membranes prepared by two different methods (LIPS: ligand induced permselectivation and RTD: rapid thermal deposition) results in a notable shift of the molecular level cut-off to smaller molecules establishing selectivity improvements from ca. 1.8 to 5 for O 2 /N 2 ; 2.2 to 32 for CO 2 /CH 4 ; 2.4 to 24 for CO 2 /N 2 ; 4.8 to 140 for H 2 /CH 4 and 5.2 to 126 for H 2 /N 2 . Furthermore, stable (based on a one-week test) oxygen-selective air separation performance at ambient temperature, 7 bar(a) feed, and 1 bar(a) sweep-free permeate with a mixture separation factor of 4.5 and oxygen flux of 2.6×10 -3 mol m -2 s -1 is established. LIPS and RTD membranes exhibit fast and gradual evolution upon a 2abIm-VPLT, respectively, reflecting differences in their thickness and microstructure. Functional reversibility is demonstrated by showing that the original permeation properties of the VPLT-LIPS membranes can be recovered upon 2mIm-VPLT.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Molecular Pivot-Hinge Installation to Evolve Topology in Rare-Earth Metal–Organic Frameworks

Linker desymmetrization has been witnessed as a powerful design strategy for the discovery of highly connected metal–organic frameworks (MOFs) with unprecedented topologies. Herein, we introduce molecular pivot-hinge installation as a linker desymmetrization strategy to evolve the topology of highly connected rare-earth (RE) MOFs, where a pivot group is placed in the center of a linker similar to a hinge. By tuning the composition of pivot groups and steric hindrances of the substituents on various linker rotamers, MOFs with various topologies can be obtained. The combination of L-SO 2 with C 2v symmetry and 12-connected RE9 clusters leads to the formation of a fascinating (4,12)-c dfs new topology. Interestingly, when replacing L-SO 2 with a tetrahedra linker L-O, the stacking behaviors of RE-organic layers switch from an eclipsed mode to a staggered stacking mode, leading to the discovery of an intriguing hjz topology. Additionally, the combination of the RE cluster and a linker [(L-(CH 3 ) 6 )] with more bulky groups gives rise to a flu topology with a new 8-c inorganic cluster. The diversity of these RE-MOFs was further enhanced through post-synthetic installation of linkers with various functional groups. Functionalization of each linker with acidic and basic units in the mesoporous RE-based PCN-90-SO 2 allows for efficient cascade catalytic transformation within the functionalized channels.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

A Pyrazine-Based Polymer for Fast-Charge Batteries

The lack of high-power and stable cathodes prohibits the development of rechargeable metal (Na, Mg, Al) batteries. Here, poly(hexaazatrinaphthalene) (PHATN), an environmentally benign, abundant and sustainable polymer, is employed as a universal cathode material for these batteries. In Na-ion batteries (NIBs), PHATN delivers a reversible capacity of 220 mAh g -1 at 50 mA g -1 , corresponding to the energy density of 440 Wh kg -1 , and still retains 100 mAh g -1 at 10 Ag -1 after 50 000 cycles, which is among the best performances in NIBs. Such an exceptional performance is also observed in more challenging Mg and Al batteries. PHATN retains reversible capacities of 110 mAh g -1 after 200 cycles in Mg batteries and 92 mAh g -1 after 100 cycles in Al batteries. DFT calculations, X-ray photoelectron spectroscopy, Raman, and FTIR show that the electron-deficient pyrazine sites in PHATN are the redox centers to reversibly react with metal ions.

25 ENERGY STORAGE↗
DOE OSTI2020

Steam-Induced Coarsening of Single-Unit-Cell MFI Zeolite Nanosheets and Its Effect on External Surface Brønsted Acid Catalysis

Commonly used methods to assess crystallinity, micro-/mesoporosity, Brønsted acid site density and distribution (in micro- vs. mesopores), and catalytic activity suggest nearly invariant structure and function for aluminosilicate zeolite MFI two-dimensional nanosheets before and after superheated steam treatment. Yet, pronounced reaction rate decrease for benzyl alcohol alkylation with mesitylene, a reaction that cannot take place in the zeolite micropores, is observed. Transmission electron microscopy images reveal pronounced changes in nanosheet thickness, aspect ratio and roughness indicating that nanosheet coarsening and the associated changes in the external (mesoporous) surface structure are responsible for the changes in the external surface catalytic activity. Finally, superheated steam treatment of hierarchical zeolites can be used to alter nanosheet morphology and regulate external surface catalytic activity while preserving micro- and mesoporosity, and micropore reaction rates.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Pillared Sn‐MWW Prepared by a Solid‐State‐Exchange Method and its Use as a Lewis Acid Catalyst

Abstract Pillared Sn‐MWW (Sn‐MWW(SP)‐SSE) was prepared through a solid‐state‐exchange (SSE) route. The pillared structure was inherited from pillared B‐MWW, and Sn was inserted in the framework by boron leaching and solid‐state‐exchange with tin tetrachloride pentahydrate. The Sn‐MWW(SP)‐SSE with framework Sn sites exhibits Lewis acidity and good catalytic performance for the Baeyer–Villiger oxidation, and mono‐ and disaccharide isomerizations.

Ren, Limin↗
DOE OSTI2017

Ring-Opening Reaction of Furfural and Tetrahydrofurfuryl Alcohol on Hydrogen-Predosed Iridium(1 1 1) and Cobalt/Iridium(1 1 1) Surfaces

The ring-opening of furfural is crucial for its conversion into value-added chemicals such as 1,5-pentanediol (1,5-PeD), an important polymer precursor. Ir-based catalysts have shown activity in ring-opening reactions, and the use of an oxophilic metal additive is reported to be beneficial. To better understand the effect of an oxophilic metal on Ir for the opening of the furan ring, a combination of DFT calculations and experimental surface science studies were performed to investigate the ring-opening of furfural and tetrahydrofurfuryl alcohol. The experimental results suggest that Co/Ir(1 1 1) has a higher ring-opening activity for an unsaturated furan ring, however, the difference in activities between Ir and Co/Ir(1 1 1) is insignificant for a saturated furan ring. The DFT results reveal that Co/Ir(1 1 1) has a stronger interaction with an unsaturated furan ring than Ir(1 1 1); both surfaces show a weaker interaction with the saturated furan ring, which causes the lower ring-opening activity than that of furfural.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Zeolite-Catalyzed Formaldehyde-Propylene Prins Condensation

Prins condensation of formaldehyde with propylene to form 3-buten-1-ol is investigated using microporous solid acid catalysts. Zn/H-beta shows high conversion but leads to a broad product distribution composed primarily of pyrans. Mechanistic studies revealed that 3-buten-1-ol reacts via Prins cyclization or dehydrate to 1,3-butadiene that further reacts with formaldehyde via a hetero-Diels–Alder reaction. These secondary reactions are suppressed over ZSM-5 catalysts: 3-buten-1-ol is the predominant product over H-ZSM-5 zeolite under all conditions investigated. 3-Buten-1-ol selectivity of up to 75 % is achieved. In a second step 3-buten-1-ol dehydrates at temperatures as low as 423 K, forming 1,3-butadiene. Although Brønsted acid sites are the primary catalytic sites, ion exchange of ZnII increases the overall rate and 3-buten-1-ol selectivity. H-ZSM-5 showed significant differences in reactivity and selectivity as a function of the Si/Al ratio; optimal catalytic properties were observed within Si/Al=40–140.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗