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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 OSTI2022

Novel Functional Thermal Energy Storage Materials for Buildings Applications

The leakage of solid-liquid phase change materials (PCMs) tremendously limits their long-term application in thermal energy storage (TES). In this work, we present durable and form-stable shape-stabilized PCMs (ss-PCMs) for TES in building envelopes. These ss-PCMs are fabricated by encapsulating polyethylene glycol (PEG) consisting of different molecular weights within mesoporous magnesium oxide and silica dioxide. For the first time, the phase transition temperature (Tt) of ss-PCMs has been fine-tuned synthetically to be comfortable to building occupants by utilizing PEG blends with molecular weights of 600 and 800 g/mol. Several parameters, including surface hydrophilicity/hydrophobicity, surface area, and PCM loading percentage, have been studied to maximize the latent heat enthalpy for high energy efficiency and maintain form stability. The best ss-PCM candidate with suitable Tt and appreciable latent heat enthalpy exhibits a repeatable phase change behavior for up to 1,000 thermal cycles without leakage, which provides a promising solution for durable TES in buildings. The Tt tunability extends its application over a wider temperature range beyond buildings.

building envelope↗
DOE OSTI2021

Benzene Ring Knitting Achieved by Ambient-Temperature Dehalogenation via Mechanochemical Ullmann-Type Reductive Coupling

The current approaches capable of affording conjugated porous networks (CPNs) still rely on solution-based coupling reactions promoted by noble metal complexes or Lewis acids, on-surface polymerization conducted in ultrahigh-vacuum environment at very high temperatures (>200 °C), or mechanochemical Scholl-type reactions limited to electron-rich substrates. To develop simple and scalable approaches capable of making CPNs under neat and ambient conditions, herein, a novel and complementary method to the current oxidative Scholl coupling processes is demonstrated to afford CPNs via direct aromatic ring knitting promoted by mechanochemical Ullmann-type reactions. The key to this strategy lies in the dehalogenation of aromatic halides in the presence of Mg involving the formation of Grignard reagent intermediates. Products (Ph-CPN-1) obtained via direct C-C bond formation between 1,2,4,5-tetrabromobenzene (TBB) monomer feature high surface areas together with mesoporous architecture. The versatility of this approach is confirmed by the successful construction of various CPNs via knitting of the corresponding aromatic rings (e.g., pyrene and triphenylene), and even highly crystalline graphite product was obtained. The CPNs exhibit good electrochemical performance as the anode material in lithium-ion batteries (LIBs). Overall, this approach expands the frontiers of CPN synthesis and provides new opportunities to their scalable applications.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Controlling the Structure of MoS 2 Membranes via Covalent Functionalization with Molecular Spacers

Restacked two-dimensional (2D) materials represent a new class of membranes for water-ion separations. Understanding the interplay between the 2D membrane’s structure and the constituent material’s surface chemistry to its ion sieving properties is crucial for further membrane development. In this paper, we reveal, and tune via covalent functionalization, the structure of MoS 2 -based membranes. We find features on both the ~1 nm (interlayer spacing) and ~100 nm (mesoporous voids between layers) length scales that evolve with the hydration level. The functional groups act as permanent molecular spacers, preventing local impermeability caused by irreversible restacking and promoting the uniform rehydration of the membrane. Molecular dynamics simulations show that the choice of functional group tunes the structure of water within the MoS 2 channel and consequently determines the hydrated interlayer spacing. We demonstrate that MoS 2 membranes functionalized with acetic acid have consistently ~92% rejection of Na 2 SO 4 with a flux of ~1.5 lm -2 hr -1 bar -1 .

2D channel↗
DOE OSTI2020

Ionic Liquid–Directed Nanoporous TiNb 2 O 7 Anodes with Superior Performance for Fast–Rechargeable Lithium–Ion Batteries

Nanoporous TiNb 2 O 7 (NPTNO) material is synthesized by a sol–gel method with an ionic liquid (IL) as the nanoporous structure directing template. NPTNO exhibits a high reversible capacity of 210 mAh g –1 even at the charging rate of 50 C and an excellent cyclability of half-cell capacity retention of 74% for 1000 cycles at 5 C and LiNi 0.5 Mn 1.5 O 4 -coupled full-cell capacity retentions of 81% and 87% for 1000 cycles at 1 C and 2 C, respectively. The studies of the 1000 cycled NPTNO electrode illustrate that the IL-directed mesoporous structure can enhance the cyclability of NPTNO cells due to the alleviation of repetitive mechanical stress and volume fluctuation induced by the repetitive Li + insertion-extraction processes. The measured Li + diffusion coefficients from the galvanostatic intermittent titration technique suggest that the IL-templating strategy indeed ensures the fast rechargeability of NPTNO cells based on the fast Li + diffusion kinetics. Benefitting from the nanoporous structure, NPTNO with unhindered Li + diffusion pathways achieves a superior rate capability in the titanium-based oxide materials and the best full-cell cyclability in the TNO materials. Furthermore, the templating potential of IL is demonstrated, and the superb electrochemical performance establishes the IL-directed NPTNO as a promising anode candidate for fast-rechargeable LIBs.

25 ENERGY STORAGE↗
DOE OSTI2025

Review—Meeting Fuel Cell Catalyst Requirements for Heavy-Duty Vehicle Applications

Catalyst requirements for proton exchange membrane (PEM) fuel cells differ by applications. Commercial heavy-duty vehicle (HDV) applications consume more H 2 fuel and demand higher durability than many others and the total cost of ownership (TCO) of the vehicle is largely related to the performance and durability of catalysts. This article is written to bridge the gap between the industrial requirements and academic activity for advanced cathode catalysts with an emphasis on durability. From a materials perspective, the underlying nature of the carbon support, Pt-alloy crystal structure, stability of the alloying element, cathode ionomer volume fraction, and catalyst-ionomer interface play a critical role in improving performance and durability. We provide our perspective on four major approaches, namely, mesoporous carbon supports, ordered PtCo intermetallic alloys, thrifting ionomer volume fraction, and shell-protection strategies that are currently being pursued. While each approach has its merits and demerits, their key developmental needs for future are highlighted.

Ramaswamy, Nagappan (ORCID:0000000234302758)↗
DOE OSTI2026

Graphene oxide precursor effects on 3D-printed carbon scaffolds

Manganese oxide (MnO 2 ), an earth-abundant material, is a promising component for energy storage devices, with uses in both pseudocapacitors and batteries. However, high MnO 2 loading often leads to reduced performance due to poor ion diffusion. 3D printing, particularly using the direct ink writing (DIW) technique, offers a solution by enabling the fabrication of electrodes with hierarchical porous structures and open channels that enhance mass transport and ion diffusion. Previous work demonstrated that 3D-printed graphene aerogels with MnO 2 coatings exhibited excellent electrochemical performance, even with thick electrodes, due to their optimized structure. Building on this work, the current study investigates the performance differences between aerogels developed using graphene oxide (GO) and reduced graphene oxide (rGO) as carbon precursors. Both materials were incorporated into thixotropic inks, 3D-printed into lattice structures, and carbonized. Despite expected similarities between the final graphene aerogel, rGO-based aerogels exhibited superior areal capacitance, compared to GO-based aerogels. These differences are attributed to the lower oxygen content and defect density of rGO, which influence its interaction with cellulose viscosifiers in the ink formulation. Brunauer–Emmett–Teller (BET) surface area analysis revealed that rGO aerogels exhibit a larger surface area and mesoporous structure, further enhancing their performance. When coated with MnO 2 , rGO-based aerogels maintained their superior capacitive behavior over GO-based aerogels. This study highlights the effect of carbon precursor on the end performance of graphene aerogels.

Materials science↗
DOE OSTI2026

Breaking the Energy Barrier of Heavy Metal Ion Diffusion in Micropores with Mesoporous 3D Graphene for Fast and Efficient Cu2+ Removal

Efficient removal of heavy metals from water critically depends not only on adsorption capacity but also on ion diffusion kinetics and the associated energy barriers. In conventional carbon adsorbents, severe diffusion confinement within micropores restricts ion transport, resulting in sluggish adsorption kinetics and large apparent activation energies despite high specific surface areas. Here, we demonstrate that this fundamental limitation is overcome by engineering meso/macroporous architectures in the 3D graphene materials synthesized via our discovered alkali-metal reactions with\\\\r\\\\n2\\\\r\\\\nCO. The unique 3D graphene materials possess defect-rich graphene frameworks with interconnected meso/macroporous networks, exhibiting simultaneously high surface area and greatly enhanced meso/macropore volume that enable efficient access to adsorption sites. As a result, the Cu2+ adsorption on 3D graphene proceeds with very low activation energies (4.98 kJ mol–1), which is almost 4 times smaller than on activated carbon (23.1 kJ mol–1). This finding offers a promising platform for efficient and sustainable water purification.

25 ENERGY STORAGE↗
DOE OSTI2024

Assessment of Amine-Based CO2BOLs for Direct Air Capture

Direct air capture (DAC) technologies extract CO 2 from the atmosphere for CO 2 storage, or utilization. Capturing CO 2 from the air is the most expensive application of carbon capture because CO 2 in the atmosphere is very dilute. There are limited number of CO 2 capture technologies for DAC application. This project aims at developing an energy efficient technology for DAC, leveraging two PNNL’s chemistries (solid and liquid CO 2 capture). Three CO 2 capture sorbents consisting of amine based CO 2 BOLs immobilized in mesoporous silica were designed, synthesized, and tested. These sorbents had ~ 19-23 wt.% amine loadings which is lower than typical amine-based silica sorbents. The surface area and pore volumes of these solid supported CO 2 BOLs are lower compared to those of the pristine silica support. The CO 2 capture performance of these materials was significantly lower than the typical silica supported amines due to low amine loading and higher molecular weight with low amine density. These results show that immobilize CO 2 BOLs in silica are not viable materials for removing CO 2 from ambient air. This project also designed, synthesized at tested liquid solvents for DAC application. Solvent properties that is vapor pressure, CO 2 uptake capacity, kinetics, and viscosity for three novel solvents were evaluated. The CO 2 uptake capacity for one of the most promising amine-based solvent BEPBEGDA was the highest at 13.2 wt% corresponding to 97 mol%. The vapor pressure of the BEPBEGDA solvents were very low at 80 °C compared to other solvents making them suitable for DAC application. The effect of humidity on the CO 2 capture performance of these solvents was evaluated which shows that presence of moisture doesn’t have a negative effect on the CO 2 uptake performance but makes it slightly better. The performances of these solvents were slightly below that of the 0.1M NaOH solution tested under similar conditions. Despite of the slightly lower CO 2 uptake, it is expected that these liquid solvents will have lower regeneration temperature and minimum evaporative losses due their low vapor pressure. Future work will focus on optimization of the liquid solvents for DAC application to improve both CO 2 capture efficiency and capacity without viscosity and vapor pressure increase. Testing of these solvents under DAC conditions using a gas liquid contactor that mimic industrial applications is needed. Solvent cost projection, techno-economic analysis and life cycle analysis are required to evaluate economic viability of this technology.

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

Intrinsically sodiophilic, mesoporous metal-free wetting layers based on inexpensive carbon black for sodium-metal batteries

In this article, elevated temperature molten Na batteries are seeing a resurgence of interest for low-cost electrochemical energy storage for the grid. Of the many recent innovations in this battery concept, new methods focused on intermediate temperature operation (e.g. 110–190 °C) have gained prominence as a way to enable comparable performance with less thermal energy loss and lower-cost materials of construction. However, the poor wettability of molten Na on suitable solid-electrolyte separators such as sodium Beta Alumina Solid-Electrolyte (Na-β”-Al 2 O 3 , ‘BASE’) requires continued innovation in interface engineering to promote full utilization of the solid-electrolyte surface area and minimize cell resistance. There have been many successful approaches to improve Na-wettability to-date including heat treatment in an inert atmosphere to remove adsorbed surface species, deposition of alloying metals such as Pb, Sn, or Bi, and use of carbon-based interfacial layers. However, these approaches either lack the ability to provide good wetting at very low temperatures (near the melting point of Na) or rely on non-scalable processes and/or toxic/expensive metals. To solve these issues, a new carbon-based sodiophilic treatment is demonstrated, which utilizes inexpensive components to form a meso/macroporous sodiophilic layer, is easily applied via drop-casting or spray-coating, provides excellent wetting as low as 110 °C, and is completely metal-free. It is found that the good sodium wetting can be attributed to the wider range of pore sizes in the carbon layers demonstrated in this study. Na wetting may occur as surface tension is initially broken by larger pores, followed by the intrusion of molten Na into smaller pores due to the apparent intrinsic affinity of Na-metal for carbon surfaces, in conjunction with the capillarity effect. Low cell-level area specific resistances of 20–30 and 13–15 Ω·cm 2 are demonstrated at 110 and 140 °C respectively. Finally, the utility of this metal-free wetting layer for solid-Na anodes is explored, showing that the metal-free wetting layer can reach a critical current density of 1.88 mA·cm -2 at 30 °C.

25 ENERGY STORAGE↗
DOE OSTI2024

Impact of Asymmetric Microstructure on Ion Transport in Ti 3 C 2 T x Membranes

Consolidation or densification of low-dimensional MXene materials into membranes can result in the formation of asymmetric membrane structures. Nanostructural (short-range) and microstructural (long-range) heterogeneity can influence mass transport and separation mechanisms. Short-range structural dynamics include the presence of water confined between the 2D layers, while long-range structural properties include the formation of defects, micropores, and mesopores. Herein, it is demonstrated that structural heterogeneity in Ti 3 C 2 T x membranes fabricated via vacuum-assisted filtration significantly affects ion transport. Higher ion permeabilities are achieved when the dense “bottom” side of the membrane, rather than the porous “top” side, faces the feed solution. Characterization of the membrane reveals distinct differences in flake alignment, surface roughness, and porosity across the membrane. In conclusion, the directional dependence on permeability suggests that one region of the membrane experiences stronger internal concentration polarization, potentially suppressing permeability through the porous side of the membrane.

MXene↗
DOE OSTI2022

Controlling Pinhole Radius and Areal Density in a-Si/SiOx Using Metal-Assisted Chemical Etching

Polysilicon on silicon oxide (poly-Si/SiOx) passivating contacts with predominant charge-carrier transport via pinholes are currently prepared via a>1000 degrees C thermal step to induce oxide break-up. Herein, we develop the precursor of a pinhole-enabled poly-Si/SiOx contact utilizing room temperature metal-assisted chemical etching (MACE) to form pinholes in the SiOx. The pinholes were created via electroless Ag nanoparticle (Ag NP) deposition followed by the MACE of intrinsic amorphous hydrogenated silicon (a-Si:H) on SiOx, creating isolated mesopores through the film stack. By varying the MACE etching solution (HF:H2O2) concentration, we were able to vary the pinhole areal density over four orders of magnitude (104-107 cm-2). We observed the Ostwald ripening of the Ag NP to enable control over the pinhole radii. Our work demonstrates proof-of-concept for a-Si:H/SiOx with mesopores across the film stack, which may serve as precursor for the development of poly-Si/SiOx passivating contacts of both polarities.

MATERIALS SCIENCE,SOLAR ENERGY↗
DOE OSTI2023

Influence of Pore Length on Hydrogenolysis of Polyethylene within a Mesoporous Support Architecture

Due to the plastic waste crisis, selective chemical upcycling of polyolefins into value-added products is a topic of intense interest, demanding polymer deconstruction processes that afford control over the product chain lengths. Recently, a catalytic architecture was synthesized in which a polyolefin melt infiltrates a porous support, and its chains are cleaved by a metal nanoparticle catalyst at the bottom of the pores, yielding a narrow distribution of alkane products. Although the influence of various parameters of these catalytic materials, including the effects of the nanoparticle size and pore diameter on product chain length, has been examined before, here, we investigate the role of the pore length in the cleavage process through the first study that combines catalytic hydrogenolysis and coarse-grained modeling to gain insights not available by experiment alone. We show that the pore length can permit control over the average product length with qualitative agreement between experiment and simulation. In conclusion, we go beyond this observation to uncover the dynamic phenomenon responsible for the pore-length dependence of the cleavage products.

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

Probing the Li 4 Ti 5 O 12 Interface Upon Lithium Uptake by Operando Small Angle Neutron Scattering

The formation of a solid–electrolyte interphase (SEI) on the surface of Li 4 Ti 5 O 12 (LTO) has become a highly controversial topic, with arguments for it and against it. However, prior studies supporting the formation of an SEI layer have typically suggested that a layer forms upon cycling of a cell, although the layer is probed after disassembling. In this study, cubic mesostructured LTO is synthesized with crystallite domain sizes between 3 and 4 nm and uniform pores with diameters ≤8 nm. The mean pore size is controlled between 4–8 nm through the use of a triblock amphipathic copolymer with a tunable hydrophobic block as template and by thermal treatment. The LTO morphology obtained is spherical and evolves upon heat treatment. We report these materials show excellent electrochemical performance, including high rate capability and capacity retention. The LTO material is subjected to operando small-angle neutron scattering and X-ray photoelectron spectroscopy experiments, which reveal that the highly debated SEI forms at potentials as high as 2.2 V, first as a LiF-rich layer and subsequently by the growth of a carbonaceous layer. These SEI products form first on the smaller pores before forming on the mesopores.

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

Structure and reactive properties of Nb-impregnated two-dimensional pillared MWW zeolites for total oxidation of volatile organic compounds

In this work, the structure and reactive properties of niobium (Nb)-impregnated MWW-type materials were evaluated for gas-phase total oxidation of volatile organic compounds, including BTX (benzene, toluene and o -xylene). The role of the type of structure (two or three-dimensional) and the loading of Nb were considered. The results indicated most Nb species with a tetrahedral coordination on the external surfaces of both two- and three-dimensional zeolites, together with a minimal contribution of octahedral extra-framework Nb 2 O 5 species. The texture and Nb content played a key role in the gas-phase total oxidation of BTX. With the same Nb content (5 wt%), the pillared zeolite exhibited a higher specific surface, larger pore volume and mesopores between the MWW nanosheets when compared to the MCM-22 zeolites, which resulted in high accessibility of the reactant molecules to the active sites, reflected in higher BTX conversion at lower and higher temperatures (50–300 °C). The best performance was achieved with the pillared zeolite (10 wt% Nb), reaching a BTX conversion at 300 °C of 92%, 69% and 58%, respectively. Here, the catalyst was stable for up to 30 h of reaction.

36 MATERIALS SCIENCE↗