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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

CFD Modeling of High-Flux Plate-and-Frame Membrane Modules for Industrial Carbon Capture

In this work, we explore the use of CO2-selective flat sheet membranes for capturing CO2 from point sources. We employ Computational Fluid Dynamics (CFD) models to design high-flux plate-and-frame membrane modules to achieve uniform flow distribution among membrane elements, minimize dead-end zones, and ease the common concentration polarization issue for gas separation membranes. The goal is to drive membrane technology improvements by providing better module designs for given membrane properties and operating conditions.

Dosso, Cheick↗
DOE OSTI2024

CFD modeling of high-flux plate-and-frame membrane modules for industrial carbon capture

In this work, we explore the use of CO2-selective flat sheet membranes for capturing CO2 from point sources. We employ Computational Fluid Dynamics (CFD) models to design high-flux plate-and-frame membrane modules to achieve uniform flow distribution among membrane elements, minimize dead-end zones, and ease the common concentration polarization issue for gas separation membranes. The goal is to drive membrane technology improvements by providing better module designs for given membrane properties and operating conditions.

Dosso, Cheick↗
DOE OSTI2020

Ion-gated carbon molecular sieve gas separation membranes

Membrane technology lies at the heart of many industrial gas separation processes and applications. Molecular sieving membranes that break the Robeson limit are desirable for energy-efficient gas separation. In this paper, we report a facile strategy of directly integrating ionic liquids (ILs) into porous membranes. Particularly, the ILs form an ultra-thin layer on the carbon molecular sieve (CMS) membranes rather than penetrating into the pores, acting as a smart gate for gas entry to boost the selectivity. The hybrid membrane exhibits CO 2 permeability >600 barrer and enhanced CO 2 /N 2 selectivity >50, which surpasses the Robeson limit and shows potential in CO 2 /N 2 separation process. Molecular dynamics simulations confirm the gating effect of the IL layer of molecular thickness. In conclusion, this work demonstrates a universal strategy to improve CMS membrane performance by creating an IL-membrane interface and tuning the ion-pore interaction.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Design and operational considerations of catalytic membrane reactors for ammonia synthesis

Production of ammonia using hydrogen derived from renewable electricity instead of hydrocarbon reforming would dramatically reduce the carbon footprint of this commodity chemical. Novel technologies such as catalytic membrane reactors may potentially be more compatible with distributed ammonia production than the conventional Haber-Bosch process. Here, a reactor model is developed based on integrating a standard industrial iron catalyst into a catalytic membrane reactor (CMR) equipped with an inorganic membrane that is selective to NH 3 over N 2 /H 2 . CMR performance is studied as functions of wide ranges of membrane properties and operating conditions. Conversion and ammonia recovery are dictated principally by the ammonia permeance, and the benefits by using membranes become significant above 100 GPU = 3.4 × 10 –8 mol m –2 s –1 Pa –1 . To be effective, the CMR requires a minimum selectivity for ammonia of 10 over both nitrogen and hydrogen, and purity scales with the effective selectivity. Increasing the pressure of operation significantly improves all metrics, and at P = 30 bar with a quality membrane ammonia is almost completely recovered, enabling direct recycle of un-reacted hydrogen and nitrogen without need for recompression. Temperature drives conversion and scales monotonically without thermodynamic limitations in a CMR. Alternatively, the temperature may be reduced as low as 300°C while achieving conversion levels surpassing equilibrium limits at T = 400°C in a conventional reactor.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Using Al 3+ to Tailor Graphene Oxide Nanochannels: Impact on Membrane Stability and Permeability

Graphene oxide (GO) membranes, which form from the lamination of GO sheets, attract much attention due to their unique nanochannels. There is much interest in controlling the nanochannel structures and improving the aqueous stability of GO membranes so they can be effectively used in separation and filtration applications. This study employed a simple yet effective method of introducing trivalent aluminum cations to a GO sheet solution through the oxidation of aluminum foil, which modifies the nanochannels in the self-assembled GO membrane by increasing the inter-sheet distance while decreasing intra-sheet spacing. The Al 3+ modification resulted in an increase in membrane stability in water, methanol, ethanol, and propanol, yet decreased membrane permeability to water and propanol. These changes were attributed to strong interactions between Al 3+ and the membrane oxygenated functional groups, which resulted in an increase in membrane hydrophobicity and a decrease in the intra-sheet spacing as supported by surface tension, contact angle, atomic force microscopy, and X-ray photoelectron spectroscopy measurements. Our approach for forming Al 3+ modified GO membranes provides a method for improving the aqueous stability and tailoring the permeation selectivity of GO membranes, which have the potential to be implemented in vapor separation and fuel purification applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Improved Hydrogen Sensitivity and Selectivity in PdO with Metal-Organic Framework Membrane

Metal-organic frameworks (MOFs) are highly designable porous materials and are recognized for their exceptional selectivity as chemical sensors. However, they are not always suitable for incorporation with existing sensing platforms, especially sensing modes that rely on electronic changes in the sensing material (e.g., work-function response or conductometric response). One way that MOFs can be utilized is by growing them as a porous membrane on a sensing layer and using the MOF to affect the electronic structure of the sensing layer. In this paper, a proof-of-concept for electronic modulation with MOFs is demonstrated. A PdO nanoparticle sensing layer on a chemical-sensitive field-effect-transistor is made more sensitive to a reducing gas, hydrogen, and less sensitive to oxidizng molecules, like H 2 S and NO 2 , by growing a layer of the MOF “ZIF-8” over the nanoparticles. The proposed mechanism is supported by X-ray photoelectron spectroscopy showing that the ZIF-8 membrane partially reduces the PdO sensing layer.

Gardner, David W. (ORCID:0000000193518391)↗
DOE OSTI2020

Computational Evaluation of Carriers in Facilitated Transport Membranes for Postcombustion Carbon Capture

Incorporating molecular amines as mobile carriers in facilitated transport membranes (FTMs) has been demonstrated to significantly enhance the CO 2 permeance and CO 2 /N 2 selectivity of the membrane for CO 2 capture from flue gas. In this study, by employing computational techniques including density functional theory calculations and molecular simulations, the role of mobile carriers has been systematically studied at a molecular level from the perspectives of the amine–CO 2 reaction chemistry, diffusivities of carriers and gases, and N 2 solubility. The latter two properties were also investigated as a function of water uptake. The water uptake values of FTMs were experimentally quantified too. The introduction of mobile carriers was shown to substantially enhance the diffusivities of CO 2 reaction products compared to FTMs without mobile carriers. The choice of mobile carriers was also demonstrated to influence the separation performance. Computationally, 2-(1-piperazinyl)ethylamine sarcosinate (PZEA-Sar) exhibited a faster reaction kinetics and slightly higher CO 2 absorption capacity as compared to piperazine glycinate (PZ-Gly). Experimentally, the FTM incorporating PZEA-Sar mobile carriers also showed a higher CO 2 permeance. The good agreement validated the computational models employed and insights generated in this study. In conclusion, the outcomes of this work shed light on the future design and selection of carrier structures, and the adopted computational approaches can be employed to discover promising mobile carrier candidates.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2023

Electrically Driven Ion Separations in Permeable Membranes

Ion separations are critical for producing materials such as Li and rare-earth element salts that are essential for applications including energy storage and production. This research aimed to develop and understand separations of singly and multiply charged ions as well as separations among different singly charged ions such as Li + and Na + . Thin layers of polyelectrolytes on membranes allow passage of singly charged ions at rates 1000 times faster than those for multiply charged ions. This allows purification of mixtures with equal concentrations of Li + and Mg 2+ to create a permeate solution with >99% Li + . Such membranes may also effectively isolate rare earth elements. To separate Li + and K + , this work developed opposing flow and current in membranes. The current overcomes the flow of K + to allow Li + to selectively pass through the membrane, leading to Li + /K + selectivities around 70. All of the research employs modelling to better understand the mechanism of these separations, which includes transport driven by gradients in electrical potential, concentration, and pressure. The interplay of these driving forces can create highly selective separations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Affinity of small-molecule solutes to hydrophobic, hydrophilic, and chemically patterned interfaces in aqueous solution

Significance Increasing global population, urbanization, and climate change pose tremendous constraints on water availability. While membrane processes offer attractive, energy-efficient options, transformative advances in membrane technology are needed to enable reuse of poor-quality waters from diverse sources. This work brings fundamental understanding of solute–surface interactions to membrane phenomena, including selectivity and fouling. Molecular simulations reveal limitations of traditional predictive measures of solute–surface partitioning, suggesting alternative thermodynamic signatures for solute binding that highlight the contextual nature of hydrophobicity. An inverse design algorithm provides a tool to pattern membrane nanoscale chemistry to optimize solute affinity and selectivity. This work demonstrates how simulations can inform practical materials design for sustainable water treatment and, more broadly, many technologies involving water-mediated solute–surface interactions.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Biocatalytic Membranes for Carbon Capture and Utilization

Innovative carbon capture technologies that capture CO 2 from large point sources and directly from air are urgently needed to combat the climate crisis. Likewise, corresponding technologies are needed to convert this captured CO 2 into valuable chemical feedstocks and products that replace current fossil-based materials to close the loop in creating viable pathways for a renewable economy. Biocatalytic membranes that combine high reaction rates and enzyme selectivity with modularity, scalability, and membrane compactness show promise for both CO 2 capture and utilization. This review presents a systematic examination of technologies under development for CO 2 capture and utilization that employ both enzymes and membranes. CO 2 capture membranes are categorized by their mode of action as CO 2 separation membranes, including mixed matrix membranes (MMM) and liquid membranes (LM), or as CO 2 gas–liquid membrane contactors (GLMC). Because they selectively catalyze molecular reactions involving CO 2 , the two main classes of enzymes used for enhancing membrane function are carbonic anhydrase (CA) and formate dehydrogenase (FDH). Small organic molecules designed to mimic CA enzyme active sites are also being developed. CO 2 conversion membranes are described according to membrane functionality, the location of enzymes relative to the membrane, which includes different immobilization strategies, and regeneration methods for cofactors. Parameters crucial for the performance of these hybrid systems are discussed with tabulated examples. Progress and challenges are discussed, and perspectives on future research directions are provided.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Investigating microstructure evolution in block copolymer membranes

Block copolymer self-assembly in conjunction with nonsolvent-induced phase separation (SNIPS) has been increasingly leveraged to fabricate integral-asymmetric membranes. The large number of formulation and processing parameters associated with SNIPS, however, has prevented the reliable construction of high performance membranes. In this study, we apply dynamical self-consistent field theory to model the SNIPS process and investigate the effect of various parameters on the membrane morphology: solvent selectivity, nonsolvent selectivity, initial film composition, and glass transition composition. We examine how solvent selectivity and concentration of polymers in the film impact the structure of micelles that connect to form the membrane matrix. In particular, we find that preserving the order in the surface layer and forming a connection between the supporting and surface layer are nontrivial and sensitive to each parameter studied. Furthermore, the effect of each parameter is discussed, and suggestions are made for successfully fabricating viable block copolymer membranes.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Durable and Highly Selective Ion Transport of a Sulfonated Diels Alder Poly(phenylene) for Vanadium Redox Flow Batteries

In order to improve the durability and ion selectivity of a hydrocarbon membrane for vanadium redox flow batteries (VRFBs) a polymer was rationally designed with an external hydrophobic shell and internal hydrophilic core. The polymer was designed to prevent hydrophilic polymer chain aggregation by functionalizing the external polymer shell with hydrophobic side chains and attaching acid moieties onto the polymer backbone. The hydrophobic shell is the result of pentafluorobenzoyl group functionalization on the pendent aryl rings in a Diels Alder poly(phenylene) backbone. The internal polymer chain contains sulfonic acid moieties to impart hydrophilic character. The physical and electrochemical characteristics of the membrane were systematically studied and compared with widely used Nafion-212. The synthesized membranes were found to be superior to Nafion-212 not only in terms of lower vanadium ion permeability (4.25 x 10 -8 vs. Nafion-212: 6.0 x 10 -6 cm 2 min -1 ) but also in higher VRFB performance (EE = 89% and vs. Nafion-212: 85.5% at 40 mA/cm 2 ). The membrane also showed over three times higher capacity retention than Nafion-212 (0.075 % vs. 0.25 % capacity loss per cycle respectively) and excellent ex situ and in situ chemical stability.

25 ENERGY STORAGE↗
DOE OSTI2022

Convenient Confinement: Interplay of Solution Conditions and Graphene Oxide Film Structure on Rare Earth Separations

Graphene oxide (GO) membranes are excellent candidates for a range of separation applications, including rare earth segregation and radionuclide decontamination. Understanding nanoscale water and ion behavior near interfacial GO is critical for groundbreaking membrane advances, including improved selectivity and permeability. Here, we experimentally examine the impact of solution conditions on water and lanthanide interactions with interfacial GO films and connect these results to GO membrane performance. The investigation of the confined films at the air–water interface with a combination of surface-specific spectroscopy and X-ray scattering techniques allows us to understand water and ion behaviors separately. Sum frequency generation spectroscopy reveals a dramatic change in interfacial water organization because of graphene oxide film deprotonation. Interfacial X-ray fluorescence measurements show a 17× increase in adsorbed lanthanide to the GO film from subphase pH 3 to pH 9. Liquid surface X-ray reflectivity data show an additional 2.7 $e^–$ per Å 2 for GO films at pH 9 versus pH 3 as well. These results are connected to GO membrane performance, which show increased selectivity and decreased flux for membranes filtering pH 9 solutions. We posit insoluble lanthanide hydroxides form at higher pHs. Taken together, these results highlight the importance of interfacial experiments on model GO systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Visualization, understanding, and mitigation of process-induced-membrane irregularities in gas diffusion electrode-based polymer electrolyte membrane fuel cells

Polymer electrolyte membrane fuel cells (PEMFC) show substantial promise for their application in electric vehicles. For large-scale manufacturing of PEMFCs, roll-to-roll coated gas-diffusion-electrodes (GDE) offer certain advantages over other production pathways. Procedures including hot pressing and coating an ionomer overlayer may be necessary for this manufacturing pathway to enable a suitable catalyst layer/membrane interface. The same procedures may potentially introduce membrane irregularities, especially when thin membranes are used. Limited understanding exists regarding if and to what extent such irregularities impact PEMFC performance and lifetime, and therefore be considered defects. In this study, NREL's customized fuel cell hardware that enables quasi in-situ infrared (IR) thermography studies was utilized to visualize spatial hydrogen crossover and identify membrane irregularities that originated from the GDE-based MEA fabrication process. The structure of these membrane irregularities was investigated by scanning electron microscopy (SEM) and its impact on initial H2/air performance was determined. Accelerated stress testing (AST) revealed that these irregularities develop into failure point locations. These results were validated across many MEAs with identified process-induced membrane irregularities. By selecting specific gas diffusion media properties and by fine tuning the MEA hot pressing parameters, the formation of such membrane irregularities was mitigated.

08 HYDROGEN↗
DOE OSTI2023

Single-Molecule Fluorescence Investigations of Solute Transport Dynamics in Nanostructured Membrane Separation Materials

Many materials used for membrane separations comprise of nanoscale structures such as pores and domains. Such nanostructures often control the solute permeability and selectivity of separation membranes. Thus, for future development of highly efficient separation membranes, it is important to understand the structural and chemical properties of these nanostructures, and also their influences on solute transport dynamics. For the last two decades, single-molecule fluorescence techniques have been used to measure the detailed dynamics of solute molecules diffusing in various nanostructured materials, giving valuable insights into molecular transport mechanisms influenced by nanoscale material heterogeneity. This Perspective will discuss recent single-molecule fluorescence studies on solute diffusion in materials relevant to membrane separations, including dense polymer films and nanoporous materials. These studies have revealed the formation and properties of nanostructures, and unique transport dynamics of solute molecules manipulated by their confinement and partitioning to the nanostructures, which play key roles in membrane separations. Furthermore, this Perspective will also point out scientific challenges toward thorough understanding of molecular-level mechanisms in membrane separations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗