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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 811 records · Page 45
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Genomic characterization of rare earth binding by Shewanella oneidensis

Abstract Rare earth elements (REE) are essential ingredients of sustainable energy technologies, but separation of individual REE is one of the hardest problems in chemistry today. Biosorption, where molecules adsorb to the surface of biological materials, offers a sustainable alternative to environmentally harmful solvent extractions currently used for separation of rare earth elements (REE). The REE-biosorption capability of some microorganisms allows for REE separations that, under specialized conditions, are already competitive with solvent extractions, suggesting that genetic engineering could allow it to leapfrog existing technologies. To identify targets for genomic improvement we screened 3,373 mutants from the whole genome knockout collection of the known REE-biosorbing microorganism Shewanella oneidensis MR-1. We found 130 genes that increased biosorption of the middle REE europium, and 112 that reduced it. We verified biosorption changes from the screen for a mixed solution of three REE (La, Eu, Yb) using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) in solution conditions with a range of ionic strengths and REE concentrations. We identified 18 gene ontologies and 13 gene operons that make up key systems that affect biosorption. We found, among other things, that disruptions of a key regulatory component of the arc system ( hptA ), which regulates cellular response to anoxic environments and polysaccharide biosynthesis related genes ( wbpQ , wbnJ , SO_3183 ) consistently increase biosorption across all our solution conditions. Our largest total biosorption change comes from our SO_4685 , a capsular polysaccharide (CPS) synthesis gene, disruption of which results in an up to 79% increase in biosorption; and nusA, a transcriptional termination/anti-termination protein, disruption of which results in an up to 35% decrease in biosorption. Knockouts of glnA , pyrD , and SO_3183 produce small but significant increases (≈ 1%) in relative biosorption affinity for ytterbium over lanthanum in multiple solution conditions tested, while many other genes we explored have more complex binding affinity changes. Modeling suggests that while these changes to lanthanide biosorption selectivity are small, they could already reduce the length of repeated enrichment process by up to 27%. This broad exploratory study begins to elucidate how genetics affect REE-biosorption by S. oneidensis , suggests new areas of investigation for better mechanistic understanding of the membrane chemistry involved in REE binding, and offer potential targets for improving biosorption and separation of REE by genetic engineering.

Medin, Sean↗
DOE OSTI2026

Nanometer Scale Imaging to Develop Quantitative Descriptors of Bipolar Membrane Junction Structure

Swings in pH can be achieved by electrically polarizing a bipolar membrane (BPM) to drive water dissociation at the BPM junction for electrochemical conversion and separation processes. BPM junction design is critical to tailor performance for specific applications; however, characterization techniques capable of resolving the nanometer scale physical structure of the junction are limited. We present sample preparation, imaging, and analysis workflows that are adaptable to a variety of BPM junction architectures. Atomic force microscopy produces BPM junction images with nanometer scale lateral resolution for samples with and without a graphene oxide water dissociation catalyst in the junction. Subsequent image segmentation and analysis quantify line edge roughness and catalyst layer thickness as descriptors of junction structure. Comparison of pre- and post-electrodialysis junctions suggests electric field-induced alignment of catalyst particles during electrodialysis. This characterization workflow can inform manufacturing protocols, computational modeling, and failure mode analysis for next-generation BPMs.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2026

A mathematical design framework for membrane pre-concentration in energy-efficient recovery of fermentation products

Due to the dilute nature of products manufactured via fermentation and cell-free bioprocessing, dewatering is a common unit operation in downstream processing (DSP) for bioproduct recovery, but it is typically energy intensive. To improve DSP energy efficiency for bio-based small molecules, integrating high-pressure membrane pre-concentration is a promising process option. However, this approach is typically constrained by a tradeoff between concentration factor (CF) and product recovery (PR), namely increasing the CF typically results in greater product loss, and vice versa. Here we developed a model that enables process design guidelines to: (i) identify scenarios in which the additional energy consumption and product loss from membrane pre-concentration are justified for use in DSP, and (ii) determine the optimal CF that minimizes process specific energy consumption. We compared the energy consumption of high-pressure membrane-integrated processes to evaporation-only processes and applied the model to an experimental case study for the separation and purification of butyric acid from Clostridium tyrobutyricum fermentation using an in situ product recovery (ISPR) process. The model estimated that integrating a tangential-flow reverse osmosis (RO) pre-concentration unit could reduce process energy consumption up to 45%. The use of advanced membrane pre-concentration technologies, such as negative rejection membranes and organic solvent reverse osmosis (OSRO), have the potential to further reduce the overall process specific energy consumption up to 96%, projected based on modeling. Overall, membrane pre-concentration, especially when strategically integrated prior to an evaporation step with optimized process conditions, holds significant potential for improving DSP energy efficiency, particularly in applications requiring substantial solvent removal for product recovery from dilute mixtures.

09 BIOMASS FUELS↗
DOE OSTI2023

Selective permeation up a chemical potential gradient to enable an unusual solvent purification modality

The need for energy-efficient recovery of organic solutes from aqueous streams is becoming more urgent as chemical manufacturing transitions toward nonconventional and bio-based feedstocks and processes. In addition to this, many aqueous waste streams contain recalcitrant organic contaminants, such as pharmaceuticals, industrial solvents, and personal care products, that must be removed prior to reuse. We observe that rigid carbon membrane materials can remove and concentrate organic contaminants via an unusual liquid-phase membrane permeation modality. Surprisingly, detailed thermodynamic calculations on the chemical potential of the organic contaminant reveal that the organic species has a higher chemical potential on the permeate side of the membrane than on the feed side of the membrane. This unusual observation challenges conventional membrane transport theory that posits that all permeating species move from high chemical potential states to lower chemical potential states. Based on experimental measurements, we hypothesize that the organic is concentrated in the membrane relative to water via favorable binding interactions between the organic and the carbon membrane. The concentrated organic is then swept through the membrane via the bulk flow of water in a modality known as “sorp-vection.” We highlight via simplified nonequilibrium thermodynamic models that this “uphill” chemical potential permeation of the organic does not result in second-law violations and can be deduced via measurements of the organic and water sorption and diffusion rates into the carbon membrane. Moreover, this work identifies the need to consider such nonidealities when incorporating unique, rigid materials for the separations of aqueous waste streams.

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

Performance Analysis of a Membrane-based Ionic Liquid Desiccant (ILD) Dehumidifier

Air dehumidification through cooling is an energy-intensive process, which consumes about 20-40% of the overall energy for air-conditioning. Liquid desiccant dehumidification can separate dehumidification from space cooling and has potential to improve the cooling efficiency and reduce the overall energy consumption for air-conditioning. However, the drawbacks such as liquid carryover and corrosion, membrane contamination and blocking, limit its application. To eliminate these problems, a new dehumidifier using nonporous membrane and ionic liquid desiccant (ILD) was developed. The dehumidification performance of the new dehumidifier was characterized through a series of lab tests. Test results indicate that the new dehumidifier can achieve a moisture removal rate up to 180.3 g/h and a dehumidification effectiveness up to 12.7%. A parametric study found that the dehumidification performance is sensitive to the flowrates of the air and the ILD solution. A higher mass flow ratio between the ILD solution and the air could result in better dehumidification performance.

Wang, Lingshi↗
DOE OSTI2020

Effects of various parameters of different porous transport layers in proton exchange membrane water electrolysis

Porous transport layers (PTLs) play an important role in proton exchange membrane water electrolysis (PEMWE) cells. The PTL facilitates water and gas transport, as well as thermal and electrical conduction, and is required to sustain good contact with adjacent components. It is expected that using PTLs with variations in material properties such as structure, composition, thickness and wettability results in performance changes of the PEMWE. Here, a general mathematical PEMWE model is developed that separates and analyzes the contributions of ohmic, activation, diffusion and Nernst potentials. For model validation, three inherently different anode PTL structures (carbon paper, sintered titanium particles, and titanium felt) are operated over a range of conditions. Additionally, the effects of PTL wettability were used to verify the model using Polytetrafluoroethylene (PTFE) treated Toray papers with PTFE loading ranging from 0% to 20%. The modeling results of both PTFE treated and untreated materials show good agreement with the experimental data. Mass transport or diffusion loss is the primary reason for performance differences between PTFE treated and untreated PTLs. Sintered titanium PTLs with thicknesses above 1 mm suffer from up to 33% increased ohmic losses without indicating any obvious changes in activation and diffusion losses when compared to untreated PTLs. The losses of the cell increase when using PTFE treated Toray paper. Individual contributions are quantified and assigned to increased ohmic, activation, and diffusion losses. In conclusion, the proposed model offers insights into the overpotential contributions of a PEMWE. It is a useful tool for predicting performance of various PTL materials and can be applied for PTL development and optimization efforts.

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

A structural underpinning of the lower critical solution temperature (LCST) behavior behind temperature-switchable liquids

In this work, we use state-of-the-art X-ray scattering and molecular dynamics to analyze amine-water mixtures that show the unusual lower critical solution temperature (LCST) behavior. The goal is to provide direct experimental evidence for the entropy-lowering molecular cluster formation hypothesized as necessary for LCST behavior. Differential wide-angle X-ray scattering and pair distribution analysis and small-angle X-ray scattering measurements were combined with molecular modeling and liquid-liquid equilibrium measurements, revealing direct experimental evidence for the hypothesis. However, the response of the amine phase to accommodating water is even more subtle than the simple hypothesis suggests, with the formation of robust nanoscale reverse micelles. The techniques developed in this paper can be expected to yield insights in the use of temperature-switchable liquids in solvent extraction and other separations, and the stabilization of organelles in living cells that do not have physical membranes but do require compositional gradients to operate.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Facilely Cross-Linking Polybenzimidazole with Polycarboxylic Acids to Improve H 2 /CO 2 Separation Performance

Polybenzimidazole (PBI) with a strong size-sieving ability exhibits attractive H 2 /CO 2 separation properties for blue H 2 production and CO 2 capture. Herein, we report that PBI can be facilely cross-linked with polycarboxylic acids, oxalic acid (OA), and trans-aconitic acid (TaA) to improve its separation performance. The acids react with the amines on the PBI chains, decreasing free volume and increasing size-sieving ability. The acid doping increases H 2 /CO 2 selectivity from 12 to as high as 45 at 35 °C. Here, the acid-doped samples demonstrate stable H 2 /CO 2 separation performance when challenged with simulated syngas containing water vapor at 150 °C, which surpasses state-of-the-art polymers and Robeson’s upper bound for H 2 /CO 2 separation.

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

Asymmetric Bipolar Membrane for High Current Density Electrodialysis Operation with Exceptional Stability

Bipolar membranes (BPMs) enable isolated acidic/alkaline regions in electrochemical devices, facilitating optimized environments for electrochemical separations and catalysis. For economic viability, BPMs must attain stable, high current density operation with low overpotentials in a freestanding configuration. We report an asymmetric, graphene oxide (GrOx)-catalyzed BPM capable of freestanding electrodialysis operation at 1 A cm–2 with overpotentials <250 mV. Use of a thin anion-exchange layer improves water transport while maintaining near unity Faradaic efficiency for acid and base generation. Voltage stability exceeding 1100 h with an average drift of 70 μV/h at 80 mA cm–2 and 100 h with an average drift of −300 μV/h at 500 mA cm–2 and implementation in an electrodialysis stack demonstrate real-world applicability. Continuum modeling reveals that water dissociation in GrOx BPMs is both catalyzed and electric-field enhanced, where low pK a moieties on GrOx enhance local electric fields and high pK a moieties serve as active sites for surface-catalyzed water dissociation. These results establish commercially viable BPM electrodialysis and provide fundamental insight to advance design of next-generation devices.

Lucas, Éowyn↗
DOE OSTI2023

Chemically Stable Styrenic Electrospun Membranes with Tailorable Surface Chemistry

Membranes with tailorable surface chemistry have applications in a wide range of industries. Synthesizing membranes from poly(chloromethyl styrene) directly incorporates an alkyl halide surface-bound initiator which can be used to install functional groups via SN2 chemistry or graft polymerization techniques. In this work, poly(chloromethyl styrene) membranes were synthesized through electrospinning. After fabrication, membranes were crosslinked with a diamine, and the chemical resistance of the membranes was evaluated by exposure to 10 M nitric acid, ethanol, or tetrahydrofuran for 24 h. The resulting membranes had diameters on the order of 2–5 microns, porosities of >80%, and permeance on the order of 10,000 L/m2/h/bar. Crosslinking the membranes generally increased the chemical stability. The degree of crosslinking was approximated using elemental analysis for nitrogen and ranged from 0.5 to 0.9 N%. The poly(chloromethyl styrene) membrane with the highest degree of crosslinking did not dissolve in THF after 24 h and retained its high permeance after solvent exposure. The presented chemically resistant membranes can serve as a platform technology due to their versatile surface chemistry and can be used in membrane manufacturing techniques that require the membrane to be contacted with organic solvents or monomers. They can also serve as a platform for separations that are performed in strong acids.

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

Assessing Composite Structure in Metal–Organic Framework-Polymer Mixed-Matrix Membranes

Metal-organic frameworks (MOFs) are renowned for their tunable structure, porosity, and internal chemistry, with demonstrated applications in molecular separations, storage, and conversion. While they are widely usable, the powdery characteristics of MOF materials can be limiting for large-scale processing and implementation in devices. Incorporating MOF particles into polymer supports affords engineering solutions to overcome these issues, yet the nature of the resulting composites is difficult to assess. Here, in this work, we present spectroscopic and calorimetric methods that we believe help establish a holistic physicochemical picture of the composite structure using a series of Zr MOFs with different pore sizes as a testbed. Power law decays are observed in X-ray scattering profiles in low q-space ranging between 2.4 and 3.3, which we interpret as changes in scattering due to polymer infiltrating MOF particles. This interpretation is supported by solid-state nuclear magnetic resonance spectroscopy and differential scanning calorimetry measurements that identify populations of the MOF-associated polymer. Additionally, positron annihilation lifetime spectroscopy measurements collected on a series of composites with different MOF-polymer ratios show multiple decay constants, each correlated to a different free volume elements. In combination with the spectroscopic, calorimetric, and scattering results, we utilize the trends in decay constants as a function of polymer mass fraction to hypothesize a polymer infiltration mechanism whereby large pores are preferentially filled, followed by small pores and, later still, interstitial spaces between particles. Even with vigorous investigation of polymer, MOF, and interface characteristics, the complex and heterogeneous nature of the composites makes absolute structural assertions difficult. We envision that the approaches demonstrated here will be a useful foundation to assess and ultimately guide the design of future MOF-polymer composites.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Impact of the Cathode Pt Loading on PEMFC Contamination by Several Airborne Contaminants

Proton exchange membrane fuel cells (PEMFCs) with 0.1 and 0.4 mg Pt cm -2 cathode catalyst loadings were separately contaminated with seven organic species: Acetonitrile, acetylene, bromomethane, iso-propanol, methyl methacrylate, naphthalene, and propene. The lower catalyst loading led to larger cell voltage losses at the steady state. Three closely related electrical equivalent circuits were used to fit impedance spectra obtained before, during, and after contamination, which revealed that the cell voltage loss was due to higher kinetic and mass transfer resistances. A significant correlation was not found between the steady-state cell voltage loss and the sum of the kinetic and mass transfer resistance changes. Major increases in research program costs and efforts would be required to find a predictive correlation, which suggests a focus on contamination prevention and recovery measures rather than contamination mechanisms.

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

Biophysical and Structural Features of αβT ‐Cell Receptor Mechanosensing: A Paradigmatic Shift in Understanding T‐Cell Activation

ABSTRACT αβT cells protect vertebrates against many diseases, optimizing surveillance using mechanical force to distinguish between pathophysiologic cellular alterations and normal self‐constituents. The multi‐subunit αβT‐cell receptor (TCR) operates outside of thermal equilibrium, harvesting energy via physical forces generated by T‐cell motility and actin‐myosin machinery. When a peptide‐bound major histocompatibility complex molecule (pMHC) on an antigen presenting cell is ligated, the αβTCR on the T cell leverages force to form a catch bond, prolonging bond lifetime, and enhancing antigen discrimination. Under load, the αβTCR undergoes reversible structural transitions involving partial unfolding of its clonotypic immunoglobulin‐like (Ig) domains and coupled rearrangements of associated CD3 subunits and structural elements. We postulate that transitions provide critical energy to initiate the signaling cascade via induction of αβTCR quaternary structural rearrangements, associated membrane perturbations, exposure of CD3 ITAMs to phosphorylation by non‐receptor tyrosine kinases, and phase separation of signaling molecules. Understanding force‐mediated signaling by the αβTCR clarifies long‐standing questions regarding αβTCR antigen recognition, specificity and affinity, providing a basis for continued investigation. Future directions include examining atomistic mechanisms of αβTCR signal initiation, performance quality, tissue compliance adaptability, and T‐cell memory fate. The mechanotransduction paradigm will foster improved rational design of T‐cell based vaccines, CAR‐Ts, and adoptive therapies.

Immunology↗
DOE OSTI2020

Electrochemical devices and fuel cell systems

Electrochemical devices including electrochemical pumps (ECPs) and fuel cell systems comprising a fuel cell and an ECP are disclosed. In particular, this electrochemical device can be an ECP that comprises an anode, a cathode and an anion exchange polymer separating the anode from the cathode. The ECP can be coupled to a hydroxide exchange membrane fuel cell (HEMFC) that is disclosed herein as a fuel cell system. These devices can be used in methods for removing carbon dioxide from air and for generating electricity.

Yan, Yushan↗
DOE OSTI2023

A Lattice Boltzmann Method for Predicting Porous Transport Layer Performance During Electrolysis

Electrolysis, the splitting of water into oxygen and hydrogen using electricity, is a sustainable way to produce green hydrogen for energy storage. In polymer electrolyte membrane (PEM) water electrolysis, water is brought into contact with charged catalyst layers and electrochemically separated into oxygen and hydrogen. The hydrogen product formed at the cathode is carried through the catalyst layer for eventual collection, while the oxygen by-product formed at the anode is removed from the surface via a multiphase interaction with circulating water and a solid porous transport layer (PTL). The design of this PTL aids in the detachment and advection of the oxygen by-product and thereby plays a role in the overall efficacy of the catalyst. In this presentation, we present our initial results modeling this multiphase system using a single-component, multiphase lattice Boltzmann method. We use the Shan-Chen model describing inter-particle forces to capture both the cohesion of the water (liquid) and oxygen (gas) phases and their interaction with the PTL (solid) (Shan and Chen, 1993). We use a Carnahan-Starling equation of state to model the effective density governing these inter-particle interactions which allows us to model this relatively high density ratio system (Carnahan and Starling, 1969). With these simulations, we show that the geometry and heterogeneity of the PTL geometry plays a large role in its ability to move oxygen away from the catalyst layer and the resulting bubble structures that are formed within the PTL. The current work demonstrates these effects using synthesized PTL geometries and 2D physics, which will be extended to experimentally-imaged PTL sections and 3D algorithms in the near future.

Boltzmann↗
DOE OSTI2023

Electrochemical devices and fuel cell systems

Electrochemical devices including electrochemical pumps (ECPs) and fuel cell systems comprising a fuel cell and an ECP are disclosed. In particular, this electrochemical device can be an ECP that comprises an anode, a cathode and an anion exchange polymer separating the anode from the cathode. The ECP can be coupled to a hydroxide exchange membrane fuel cell (HEMFC) that is disclosed herein as a fuel cell system. These devices can be used in methods for removing carbon dioxide from air and for generating electricity.

Yan, Yushan↗
DOE OSTI2022

Tailoring sub-3.3 Å ultramicropores in advanced carbon molecular sieve membranes for blue hydrogen production

Carbon molecular sieve (CMS) membranes prepared by carbonization of polymers containing strongly size-sieving ultramicropores are attractive for high-temperature gas separations. However, polymers need to be carbonized at extremely high temperatures (900° to 1200°C) to achieve sub-3.3 Å ultramicroporous channels for H 2 /CO 2 separation, which makes them brittle and impractical for industrial applications. Here, we demonstrate that polymers can be first doped with thermolabile cross-linkers before low-temperature carbonization to retain the polymer processability and achieve superior H 2 /CO 2 separation properties. Specifically, polybenzimidazole (PBI) is cross-linked with pyrophosphoric acid (PPA) via H bonding and proton transfer before carbonization at ≤600°C. The synergistic PPA doping and subsequent carbonization of PBI increase H 2 permeability from 27 to 140 Barrer and H 2 /CO 2 selectivity from 15 to 58 at 150°C, superior to state-of-the-art polymeric materials and surpassing Robeson’s upper bound. This study provides a facile and effective way to tailor subnanopore size and porosity in CMS membranes with desirable molecular sieving ability.

42 ENGINEERING↗
DOE OSTI2023

High-Performance Hemofiltration via Molecular Sieving and Ultra-Low Friction in Carbon Nanotube Capillary Membranes

Conventional dialyzer membranes typically comprise of unevenly distributed polydisperse, tortuous, rough pores, embedded in relatively thick ≈20–50 µm polymer layers wherein separation occurs via size exclusion as well as differences in diffusivity of the permeating species. However, transport in such polymeric pores is increasingly hindered as the molecule size approaches the pore dimension, resulting in significant retention of undesirable middle molecules (≥15–60 kDa) and uremic toxins. Enhanced removal of middle molecules is usually accompanied by high albumin loss (≈66 kDa) causing hypoalbuminemia. Here, the scalable bottom-up fabrication of wafer-scale carbon nanotube (CNT) membranes with highly aligned, low-friction, straight-channels/capillaries and narrow pore-diameter distributions (≈0.5–4.5 nm) is demonstrated, to overcome persistent challenges in hemofiltration/hemodialysis. Using fluorescein isothiocyanate (FITC)-Ficoll 70 and albumin in phosphate buffered saline (PBS) as well as in bovine blood plasma, it is shown that CNT membranes can allow for significantly higher hydraulic permeability (more than an order of magnitude when normalized to pore area) than commercial high-flux hemofiltration/hemodialysis membranes (HF 400), as well as greatly enhance removal of middle molecules while maintaining comparable albumin retention. These findings are rationalized via an N-pore transport model that highlights the critical role of molecular flexing and deformation during size-selective transport within nanoscale confinements of the CNTs. In conclusion, the unique transport characteristics of CNTs coupled with size-exclusion and wafer-scale fabrication offer transformative advances for hemofiltration, and the obtained insight into molecular transport can aid advancements in several other bio-systems/applications beyond hemofiltration/hemodialysis.

36 MATERIALS SCIENCE↗