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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

In Operando Calorimetric Measurements for Activated Carbon Electrodes in Ionic Liquid Electrolytes under Large Potential Windows

This study aims to investigate the effect of the potential window on heat generation in carbon-based electrical double layer capacitors (EDLCs) with ionic-liquid (IL)-based electrolytes using in operando calorimetry. The EDLCs consisted of two identical activated-carbon electrodes with either neat 1-butyl-1-methylpyrrolidinium bis(trifluoromethane-sulfonyl)imide ([Pyr 14 ][TFSI]) electrolyte or 1.0 m [Pyr 14 ][TFSI] in propylene carbonate (PC) as electrolyte. The instantaneous heat generation rate at each electrode was measured under galvanostatic cycling for different potential windows ranging from 1 to 4 V. First, the heat generation rates at the positive and negative electrodes differed significantly in neat IL owing to the differences in the ion sizes and diffusion coefficients. However, these differences were minimized when the IL was diluted in PC. Second, for EDLC in neat [Pyr 14 ][TFSI] at high potential window (4 V), a pronounced endothermic peak was observed at the beginning of the charging step at the positive electrode owing to TFSI - intercalation in the activated carbon. On the other hand, for EDLC in 1.0 m [Pyr 14 ][TFSI] in PC at potential window above 3 V, an endothermic peak was observed only at the negative electrode owing to the decomposition of PC. Third, for both neat and diluted [Pyr 14 ][TFSI] electrolytes, the irreversible heat generation rate increased with increasing potential window and exceeded Joule heating. This was attributed to the effect of potential-dependent charge redistribution resistance. Additionally, a further increase in the irreversible heat generation rate was observed for the largest potential windows owing to the degradation of the PC solvent. Finally, for both types of electrolyte, the reversible heat generation rate increased with increasing potential window because of the increase in the amount of ion adsorbed/desorbed at the electrode/electrolyte interface.

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

Chiral Electrokinetic Phenomena in Single Nanopores

Abstract The arrangement of solvent molecules and ions at solid–liquid interfaces determines electrochemical properties that are important in separations platforms, sensing technologies, and energy‐storage systems. Here we show that single glass and polymer pores in contact with propylene carbonate (PC) solutions of LiClO 4 exhibit an effective surface potential that is modulated by the enantiomeric excess of the solvent. In particular, electrochemical and electrokinetic measurements of ionic transport through glass pipettes and polymer pores reveal that the effective surface potential is significantly lower in solutions prepared using enantiomerically pure PC than in solutions prepared using racemic PC. Both pore systems became positively charged in all racemic solutions examined in the range of LiClO 4 concentrations between 1 mM and 100 mM, whereas solutions in ( R )‐(+)‐PC induced a positive surface potential only at concentrations above ~5 mM. The effective surface potential is quantified through asymmetry in current–voltage curves and zeta‐potential measurements. Vibrational sum‐frequency‐generation experiments on LiClO 4 solutions in racemic and enantiomerically pure PC indicate that the surface lipid‐bilayer‐like region in the former is more strongly organized than in the latter, dictating the favorable positions for lithium and perchlorate ions in each case. The more ordered molecular packing in the racemic liquid leads to accumulation of lithium ions on the outside of the bilayer, creating a higher effective positive charge. Our results highlight the extreme sensitivity of the interfacial potential on molecular organization of the solvent, and the relatively unexplored role that chirality can play in electrokinetic phenomena.

Alanis, Kristen↗
DOE OSTI2023

Moisture ingress in commercial steel drums: Water content determination, diffusion modelling and predicted permeation rates

Commercial steel drums underpin the global economy, playing a pivotal role in the storage and transportation of critical materials. Transported and stored materials, such as food, chemical and nuclear waste, can be sensitive to ambient conditions, particularly moisture that can enhance negative effects such as corrosion and material degradation. Although international standards and regulations are in place for the qualification of steel drums, there are no current testing requirements, established limits or boundaries for the permeation of moisture into the drums during transportation or storage. This work aims to provide insights into the moisture ingress over time into properly sealed steel drums and provides estimated moisture ingress rates over time through extrapolation. Water vapour transmission rate (WVTR) measurements through the gasket material at 10–40°C were 0.11–2.1 g/m 2 /day resulting in a permeation activation energy of 30.2 kJ/mol. Water sorption measurements and Karl Fischer titration (KFT) on ethylene propylene diene monomer (EPDM) gasket material revealed a decrease in equilibrium moisture saturation with increasing temperature. KFT measurements also revealed the presence of moisture within the adhesive and drum wall after exposure to ambient conditions. KFT and Fourier transform infrared spectroscopy (FTIR) show that moisture will desorb from the EPDM and drum wall after exposure to desiccating conditions, although a minimal amount of moisture will remain present. When sealed to the manufacturer's recommendations, the steel drums are effective in minimizing moisture ingress. In conclusion, in sealed empty drums, moisture ingress rates for 19-L drums were 0.4–1.5 mg/day at 25°C 15% relative humidity (RH) and increased to 7.1–8.8 mg/day at 40°C 90% RH, and moisture ingress rates for 210-L drums were 2.5 and 3.5 mg/day at field deployment conditions of 15.5°C 51.5% RH and 23°C 40% RH, respectively.

42 ENGINEERING↗
DOE OSTI2024

Synergetic Dual‐Additive Electrolyte Enables Highly Stable Performance in Sodium Metal Batteries

Sodium (Na)-metal batteries (SMBs) are considered one of the most promising candidates for the large-scale energy storage market owing to their high theoretical capacity (1,166 mAh g -1 ) and the abundance of Na raw material. However, the limited stability of electrolytes still hindered the application of SMBs. Herein, sulfolane (Sul) and vinylene carbonate (VC) are identified as effective dual additives that can largely stabilize propylene carbonate (PC)-based electrolytes, prevent dendrite growth, and extend the cycle life of SMBs. The cycling stability of the Na/NaNi 0.68 Mn 0.22 Co 0.1 O 2 (NaNMC) cell with this dual-additive electrolyte is remarkably enhanced, with a capacity retention of 94% and a Coulombic efficiency (CE) of 99.9% over 600 cycles at a 5 C (750 mA g -1 ) rate. The superior cycling performance of the cells can be attributed to the homogenous, dense, and thin hybrid solid electrolyte interphase consisting of F- and S-containing species on the surface of both the Na metal anode and the NaNMC cathode by adding dual additives. Such unique interphases can effectively facilitate Na-ion transport kinetics and avoid electrolyte depletion during repeated cycling at a very high rate of 5 C. This electrolyte design is believed to result in further improvements in the performance of SMBs.

25 ENERGY STORAGE↗
DOE OSTI2022

Interfacial Effects on the Dielectric Properties of Elastomer Composites and Nanocomposites

Elastomer-based composites and nanocomposites are discussed, with the emphasis on the filler and interfacial effects on their dynamics, and the resulting manifestation in their macroscopic dielectric or mechanical response. Specifically, selected polydimethylsiloxane (PDMS)/barium-titanate and styrene-butadiene rubber (SBR)/graphene oxide nanocomposites are discussed, as examples where controlled spatial distribution of filler (structured composites) gives rise to significantly different dielectric and thermomechanical behaviors. Also, ethylene–propylene–diene (EPDM)/carbon black (CB) composites are presented, as examples of systems that exhibit an abnormal temperature dependence of dielectric relaxation; and this response is discussed in the context of CB cluster polarization and quantified through a simple scaling model of the same. Finally, multi-filler EPDM/CB/ceramic elastomer nanocomposites are discussed, as examples of systems with antagonistic interfacial effects between conductive and dielectric fillers, as well as with strong interphase responses that can overwhelm the dielectric contributions from the fillers; in these systems, interphasial responses result in counter-intuitive dielectric behaviors and in strong deviations from standard design principles typically employed in the design of dielectric composite systems.

Li, Bo↗
DOE OSTI2024

Catalytic conversion of post-consumer recycled high-density polyethylene oil over Zn-impregnated ZSM-5 catalysts

The catalytic conversion of post-consumer recycled high-density polyethylene (PCR-HDPE) pyrolysis oil was investigated using modified ZSM-5 zeolites, prepared under different conditions. The PCR-HDPE oil, obtained through pyrolysis at 500 °C followed by distillation at 165 °C, contained a naphtha fraction hydrocarbons suitable for catalytic upgrading. H/ZSM-5 converts PCR-HDPE naphtha fraction oil primarily into BTX, along with light paraffins and olefins. Introducing mesoporosity led to increased propylene yield at the expense of BTX. Zn impregnation onto H/ZSM-5 and H-meso/ZSM-5 enhanced BTX yield by up to 13 %. However, Zn-meso/ZSM-5 exhibited a lower BTX yield than Zn/ZSM-5 with the same Zn loadings, especially after additional steam treatment at 700 °C. Spent catalysts revealed no noticeable increase in metal contaminants such as calcium and aluminum that were present in the PCR-HDPE. Here, the Zn/ZSM-5 catalyst was stable for more than 50 h time on stream and showed promising potential for upgrading PCR-HDPE naphtha fraction oils.

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

Green co-solvent-assisted one-pot synthesis of high-performance flexible lignin polyurethane foam

Although lignin is a promising candidate as a source of polyol for producing eco-friendly polyurethane foam (PUF), its direct application has limitations, primarily stemming from the brittleness of the resulting products and poor processibility at high lignin loadings. To address these technical challenges, we introduced an effective co-solvent for the lignin-based polyurethane foams (LPUFs) with up to 80wt% of lignin substitution for petroleum polyols. As a green co-solvent that involves carbon dioxide fixation during its production, propylene carbonate (PC), was blended with lignin and improved the distribution of lignin by decreasing the viscosity, providing a room-temperature reaction. The LPUFs demonstrated a comparable thermal insulation performance (R-values greater than 5 in -1 ) with commercially available PUF with a uniform size of closed-cell structure induced by the reduced viscosity of lignin-based polyol. LPUFs also showed enhanced fire retardancy and moisture resistance compared to the control PUFs, benefiting from lignin’s intrinsic fire-resistant and hydrophobic properties. To mitigate the brittleness issue at high lignin loadings, flexible polyethylene glycols (PEGs) with a high molecular weight (i.e., PEG-1000) were dissolved in PC at room temperature to further improve the mechanical strength of LPUFs. The compressive strength of LPUFs with 80 wt% lignin substitution content was remarkably improved to 226 kPa by the employment of co-solvent and PEG-1000 compared to the control PUF (<140 kPa). Moreover, the flexibility of the LPUFs was successfully controlled by simply adjusting the PEG-400/PEG-1000 ratio. In conclusion, the results of this study provide valuable insights for accelerating and broadening the utilization of lignin in sustainable materials and manufacturing areas.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Selective depolymerization of polyolefin copolymer via high-entropy alloy catalyzed pyrolysis in a double-layered ultrafast heating reactor

Chemical recycling of polyolefin copolymers (PCPs) is essential for mitigating plastic pollution, yet achieving selective depolymerization into C 2 –C 3 monomers at high productivity remains challenging. Here, we introduce a double-layered ultrafast heating reactor (DUHR) that integrates Joule heating with a high-entropy alloy (HEA) catalyst composed of near-equimolar Co, Cu, Fe, Mn, and Ni. We achieve highly selective depolymerization of PCP into ethylene and propylene, yielding a 70% non-condensable fraction. Significant aromatic fractions form via radical-driven pathways—a behavior distinct from conventional externally heated pyrolyzers—highlighting DUHR's ability to generate reactive species and modulate reaction pathways. Furthermore, these findings demonstrate an effective strategy for chemical recycling of real-world plastic waste for polyolefin circularity and sustainable resource recovery.

Chemical recycling↗
DOE OSTI2023

Promoting propane dehydrogenation over PtFe bimetallic catalysts by optimizing the state of Fe species

Optimizing the structure of Pt-based bimetallic catalysts is of utmost importance toward improving the propane dehydrogenation performance. It is challenging to precisely synthesize uniform PtFe alloy nanoparticles without excess unalloyed Fe species on the support as these Fe species lead to low propylene selectivity, coke deposition, and poor stability. Herein, we report an effective strategy to optimize the structure of PtFe bimetallic catalysts with minimal coke and high turnover frequency (8.2 s -1 ). For the optimized catalyst, 1Pt3Fe@S-1, most Fe species is in the framework of the zeolite S-1, which significantly suppresses the formation of coke. In addition, the extra-framework Fe and Pt species encapsulated in the channel of zeolite form uniform PtFe alloy nanoparticles, which significantly improves the C 3 H 6 selectivity, catalytic stability, and recycling performance. In conclusion, these findings provide insights into the structure-performance relationship of PtFe bimetallic catalysts and shall be beneficial to future design and optimization of similar catalytic materials.

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

Heterogeneous hydroformylation of alkenes by Rh-based catalysts

Heterogeneously catalyzed hydroformylation reactions avert the problems of separation in homogeneous reactions, reduce the discharge of phosphorus-containing wastes, and prevent the loss of precious metals. This review summarizes the developments of catalysts for heterogeneous hydroformylation in the last decade and proposes potential modification methods for future improvements. The hydroformylation properties of different reactants are compared in order to emphasize the fact that various olefins face unique challenges. The hydroformylation of ethylene requires the enhancement of catalytic activity and chemoselectivity, whereas that of propylene needs improvements in both chemoselectivity and regioselectivity. The hydroformylation of longer-chain olefins and styrene seeks further improvement in regioselectivity. The catalytic properties of activity, selectivity, and stability can be tuned through electronic effects (bimetallic effects, phosphine ligands, and single-atom catalysts), steric hindrance (encapsulation structures, diphosphine ligands, and local functional groups), and reaction condition optimization (temperature, pressure, and solvents). Furthermore, the understanding of these effects is critical in future catalyst design for heterogeneous hydroformylation reactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Colocalized Raman spectroscopy – scanning electrochemical microscopy investigation of redox flow battery dialkoxybenzene redoxmer degradation pathways

Non-aqueous redox flow batteries offer high voltages for grid-level energy storage technologies. However, decomposition of the redoxmers - redox-active molecules that make up the anolyte and catholyte in the negative and positive cell compartments - is an important challenge to overcome for long-term storage. Here, we present a spectroelectrochemical study of the catholyte candidate 2,3-dimethyl-1,4-dialkoxybenzene (C7) and its decomposition mechanisms in the presence of a model nucleophilic base, pyridine. We utilize colocalized Raman microscopy and scanning electrochemical microscopy (Raman-SECM) to quantify the chemical rates of decom-position and qualitatively identify the reaction intermediates and products. A detailed study on how the Raman-SECM parameters (electrode distance, substrate electrode, and laser focal height) influence the Raman signal of the charged catholyte C7 ∙+ is presented. Using optimized conditions, we monitored the deprotonation of C7 ∙+ via Raman spectroscopy and the subsequent hydrogen abstraction from solvent molecules to regenerate C7 via electrochemistry. Finite element modeling was used to fit electrochemical and spectroscopic data, quantifying the deprotonation rates as k dep = 2000 and 700 L mol -1 s -1 and abstraction rates as k abs = 0.5 and 0.2 s - 1 in propylene carbonate and acetonitrile solvents, respectively. Our results show the value of spatiotemporal reso-lution in evaluating the chemical and electrochemical behavior of materials for redox flow batteries.

25 ENERGY STORAGE↗
DOE OSTI2023

Ion transport in non-aqueous electrolyte mixtures of zinc chloride deep eutectic solvent (DES) and molecular solvents

For this work, the ion dynamics of null solvents 1ZnCl 2 :4EtG and 1ChCl:1ZnCl 2 :6EtG incorporating 1M water, propylene carbonate (PC) or acetonitrile (AcN) were investigated using 1 H NMR spectra and spin-lattice relaxation time (T 1 ) measurements combined with ionic conductivity, density, and viscosity, all as a function of temperature. Results show that the inclusion of all co-solvents increased the available free volume of the mixtures and followed the trend H 2 O ≤ PC < AcN. 1 H NMR spectra and T 1 inferred the presence of multiple ionic species with varying rates of mobilities. These dynamic heterogeneities were displayed by the broad T 1 minima – especially for the 1ZnCl 2 :4EtG mixtures – and asymmetrically broadened linewidths. T 1 results also revealed selective interaction sites between the hydrogen bond donors and acceptors, as well as with the co-solvents.

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

High-pressure hydrogen decompression in sulfur crosslinked elastomers

High-pressure storage and cyclic (de)pressurization of hydrogen gas is known to result in degradation and failure of gas canisters, hoses, linings, and O-rings as the relatively small hydrogen molecule can readily permeate most materials. Hence, identifying material compositions that are less susceptible to hydrogen-induced damage is of significant importance to the hydrogen energy infrastructure. Here, we use classical atomistic molecular dynamics simulations to study hydrogen exposed ethylene-propylene-diene monomer (EPDM) rubber, an elastomer typically used in O-rings. We make chemical modifications to the model by adjusting the crosslink density and report on gas solubility, diffusivity, and molecular restructuring in response to rapid decompression. Our simulations indicate that increases in crosslink density can reduce volumetric expansion during decompression and result in smaller free volume pore sizes. However, these favorable properties for sealing materials come with a tradeoff. At pressure, crosslinks introduce extra free volume, providing potential sites for gas localization, the precursor to cavitation-induced failure.

08 HYDROGEN↗
DOE OSTI2025

Effects of high-pressure hydrogen exposure on filler-elastomer adhesion

Elastomers are known to gain enhanced mechanical properties through compounding with nanosized filler particles such as silica or carbon black. Filler dispersion and filler-polymer interfacial strength are key contributing factors to this improvement. The interfacial strength is critical to part lifetime in pressurized gas sealing applications such as O-rings, where weak binding between the filler particle and polymer matrix can lead to internal void structures. With the aim to build a fundamental understanding of precursors to pressurized hydrogen-induced failure in elastomers, we use all-atom molecular dynamics simulations to study the impact of hydrogen oversaturation on filler-polymer interaction strength. We systematically study the interface between a commonly used elastomer, ethylene-propylene-diene monomer (EPDM) and silica by varying gas concentration, crosslink density, and surface chemistry. Our simulations predict that decompression leads to a localization of excess gas near the interface. In conclusion, we demonstrate that this localized gas can weaken interfacial adhesion and quantify the interaction using thermodynamic approaches.

EPDM↗
DOE OSTI2020

Nonflammable Lithium Metal Full Cells with Ultra-high Energy Density Based on Coordinated Carbonate Electrolytes

Coupling thin Li metal anodes with high-capacity/high-voltage cathodes such as LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) is a promising way to increase lithium battery energy density. Yet, the realization of high-performance full cells remains a formidable challenge. Here, we demonstrate a new class of highly coordinated, nonflammable carbonate electrolytes based on lithium bis(fluorosulfonyl)imide (LiFSI) in propylene carbonate/fluoroethylene carbonate mixtures. Utilizing an optimal salt concentration (4 M LiFSI) of the electrolyte results in a unique coordination structure of Li + -FSI - -solvent cluster, which is critical for enabling the formation of stable interfaces on both the thin Li metal anode and high-voltage NCM811 cathode. Under highly demanding cell configuration and operating conditions (Li metal anode = 35 μm, areal capacity/charge voltage of NCM811 cathode = 4.8 mAh cm -2 /4.6 V, and anode excess capacity [relative to the cathode] = 0.83), the Li metal-based full cell provides exceptional electrochemical performance (energy densities = 679 Wh kg cell -1 /1,024 Wh L cell -1 ) coupled with nonflammability.

25 ENERGY STORAGE↗
DOE OSTI2023

Importance of hydrogen bonding in base-catalyzed transesterification reactions with vicinal diols

The transesterification reaction kinetics of 2-(benzoyloxy)ethyl benzoate with various alcohols (ethylene glycol, 1,3-propanediol, 1-butanol, propylene glycol and 1,2-butylene glycol) using various cyclic amidine catalysts were investigated. For transesterification with excess glycol (glycolysis), the rate was nearly zero order in diester and glycol concentration, which is substantially different from classical transesterification kinetics with mono-alcohols. The measured kinetic parameters during glycolysis are consistent with a reaction path that is kinetically limited by the decomposition of the reaction intermediate formed from the alkoxide and diester. The DFT-calculated reaction energy and activation barrier for decomposition of this intermediate reveal a critical role of intramolecular hydrogen-bond stabilization made possible by the vicinal –OH of the glycol that effectively increases the concentration of the intermediate during reaction resulting in acceleration of the overall transesterification rate. In conclusion, these findings indicate the nature of both the alcohol solvent and the catalyst influence transesterification rate, and results suggest they are also important in the deconstruction of carbonyl-containing condensation polymers.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Probing the Self-Assembly dynamics of cellulose nanocrystals by X-ray photon correlation spectroscopy

Charge-stabilized colloidal cellulose nanocrystals (CNCs) can self-assemble into higher-ordered chiral nematic structures by varying the volume fraction. The assembly process exhibits distinct dynamics during the isotropic to liquid crystal phase transition, which can be elucidated using X-ray photon correlation spectroscopy (XPCS). Anionic CNCs were dispersed in propylene glycol (PG) and water spanning a range of volume fractions, encompassing several phase transitions. Coupled with traditional characterization techniques, XPCS was conducted to monitor the dynamic evolution of the different phases. Additionally, simulated XPCS results were obtained using colloidal rods and compared with the experimental data, offering additional insights into the dynamic behavior of the system. The results indicate that the particle dynamics of CNCs undergo a stepped decay in three stages during the self-assembly process in PG, coinciding with the observed phases. The phase transitions are associated with a total drop of Brownian diffusion rates by four orders of magnitude, a decrease of more than a thousand times slower than expected in an ideal system of repulsive Brownian rods. Given the similarity in the phase behaviors in CNCs dispersed in PG and in water, we hypothesize that these dynamic behaviors can be extrapolated to other polar solvent environments. Importantly, these findings represent the direct measurement of CNC dynamics using XPCS, underscoring the feasibility of directly assessing the dynamic behavior of other rod-like colloidal suspensions.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Understanding fluorine-free electrolytes via small-angle X-ray scattering

Fluorine-free electrolytes have attracted great attention because of its low-cost and environmental friendliness. However, so far, little is known about the solution structures of these electrolytes. Here, we compare the solvation phenomenon of sodium tetraphenylborate (NaBPh 4 ) salt dissolved in organic solvents of propylene carbonate (PC), 1,2-dimethoxyethane (DME), acetonitrile (ACN) and tetrahydrofuran (THF). Small-angle X-ray scattering (SAXS) reveals a unique two-peak structural feature in this salt concentrated PC electrolyte, while solutions using other solvents only have one scattering peak. Molecular dynamics (MD) simulations further reveal that there are anion-based clusters in addition to the short-range charge ordering in the concentrated NaBPh4/PC electrolyte. Raman spectroscopy confirms the existence of considerable contact ion pairs (CIPs). Here, this work emphasizes the importance of global and local structural analysis, which will provide valuable clues for understanding the structure performance relationship of electrolytes.

25 ENERGY STORAGE↗