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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 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Thickness-independent scalable high-performance Li-S batteries with high areal sulfur loading via electron-enriched carbon framework

Abstract Increasing the energy density of lithium-sulfur batteries necessitates the maximization of their areal capacity, calling for thick electrodes with high sulfur loading and content. However, traditional thick electrodes often lead to sluggish ion transfer kinetics as well as decreased electronic conductivity and mechanical stability, leading to their thickness-dependent electrochemical performance. Here, free-standing and low-tortuosity N, O co-doped wood-like carbon frameworks decorated with carbon nanotubes forest (WLC-CNTs) are synthesized and used as host for enabling scalable high-performance Li-sulfur batteries. EIS-symmetric cell examinations demonstrate that the ionic resistance and charge-transfer resistance per unit electro-active surface area of S@WLC-CNTs do not change with the variation of thickness, allowing the thickness-independent electrochemical performance of Li-S batteries. With a thickness of up to 1200 µm and sulfur loading of 52.4 mg cm −2 , the electrode displays a capacity of 692 mAh g −1 after 100 cycles at 0.1 C with a low E/S ratio of 6. Moreover, the WLC-CNTs framework can also be used as a host for lithium to suppress dendrite growth. With these specific lithiophilic and sulfiphilic features, Li-S full cells were assembled and exhibited long cycling stability.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Gas phase synthesis of the C40 nano bowl C 40 H 10

Nanobowls represent vital molecular building blocks of end-capped nanotubes and fullerenes detected in combustion systems and in deep space such as toward the planetary nebula TC-1, but their fundamental formation mechanisms have remained elusive. By merging molecular beam experiments with electronic structure calculations, we reveal a complex chain of reactions initiated through the gas-phase preparation of benzocorannulene (C 24 H 12 ) via ring annulation of the corannulenyl radical (C 20 H 9 • ) by vinylacetylene (C 4 H 4 ) as identified isomer-selectively in situ via photoionization efficiency curves and photoion mass-selected threshold photoelectron spectra. In silico studies provided compelling evidence that the benzannulation mechanism can be expanded to pentabenzocorannulene (C 40 H 20 ) followed by successive cyclodehydrogenation to the C40 nanobowl (C 40 H 10 ) – a fundamental building block of buckminsterfullerene (C 60 ). This high-temperature pathway opens up isomer-selective routes to nanobowls via resonantly stabilized free-radical intermediates and ring annulation in circumstellar envelopes of carbon stars and planetary nebulae as their descendants eventually altering our insights of the complex chemistry of carbon in our Galaxy.

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

Solving complex nanostructures with ptychographic atomic electron tomography

Abstract Transmission electron microscopy (TEM) is essential for determining atomic scale structures in structural biology and materials science. In structural biology, three-dimensional structures of proteins are routinely determined from thousands of identical particles using phase-contrast TEM. In materials science, three-dimensional atomic structures of complex nanomaterials have been determined using atomic electron tomography (AET). However, neither of these methods can determine the three-dimensional atomic structure of heterogeneous nanomaterials containing light elements. Here, we perform ptychographic electron tomography from 34.5 million diffraction patterns to reconstruct an atomic resolution tilt series of a double wall-carbon nanotube (DW-CNT) encapsulating a complex ZrTe sandwich structure. Class averaging the resulting tilt series images and subpixel localization of the atomic peaks reveals a Zr 11 Te 50 structure containing a previously unobserved ZrTe 2 phase in the core. The experimental realization of atomic resolution ptychographic electron tomography will allow for the structural determination of a wide range of beam-sensitive nanomaterials containing light elements.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Industrializable interlayer with catalytic conversion of dead lithium for Ah–level Nickel–rich lithium metal batteries

The growth of lithium (Li) dendrites and the accumulation of dead Li (i.e., Li metal regions which are electronically disconnected from the current collector) significantly undermine the safety and performance of Li metal batteries. This study employs kilogram-scale atomic layer deposition technology to construct zinc oxide with a preferential (002) crystal orientation, which homogeneously forms on commercial carbon nanotube papers. Our approach emphasizes the importance of achieving a moderate Li adsorption energy and low Li migration energy barriers to suppress Li dendrite growth. In this work, we introduce the concept of "catalytic" effect for dead Li reconversion, as validated through time-of-flight secondary ion mass spectrometry, leading to a Li plating/stripping efficiency of 99.89%. The Ah-level Li metal pouch cells with high-nickel positive electrodes achieve a specific energy of 380 Wh kg -1 (based on the mass of the whole pouch cell) and demonstrate stable cycling under demanding conditions. Analysis of the cycled pouch cells confirms the structural integrity and provides insights into the mechanism of the dead Li "catalytic" conversion.

Shen, Huasen [Jianghan University, Wuhan (China)]↗
DOE OSTI2025

Assembled peptoid crystalline nanomaterials as carbonic anhydrase mimics for promoted hydration and sequestration of CO 2

Carbonic anhydrase (CA) mimics have received significant attention due to their promising applications in the enhanced hydration and sequestration of CO 2 . Herein, we report the assembly of sequence-defined peptoids into crystalline nanomaterials with controlled microenvironment of active sites as CA mimics for promoted hydration and sequestration of CO 2 . By incorporating specific ligands into self-assembling peptoids and coordinating these ligands with metal cations, we synthesize a variety of crystalline nanosheets and nanotubes as efficient CA mimics comparable to natural bovine CA. Molecular dynamics simulations reveal the critical roles of peptoid-Zn 2+ binding energy and the active site local microenvironment on the catalytic performance of these CA mimics. CO 2 precipitation results show that these CA mimics promote the hydration and sequestration of CO 2 while retaining high thermal and chemical stabilities. This study offers essential guidance for the future design of high-performance CA-mimics suitable for applications in CO 2 capture and sequestration.

Chakma, Progyateg [Pacific Northwest National Labo↗
DOE OSTI2022

Efficient and universal characterization of atomic structures through a topological graph order parameter

Abstract A graph-based order parameter, based on the topology of the graph itself, is introduced for the characterization of atomistic structures. The order parameter is universal to any material/chemical system and is transferable to all structural geometries. Four sets of data are used to validate both the generalizability and accuracy of the algorithm: (1) liquid lithium configurations spanning up to 300 GPa, (2) condensed phases of carbon along with nanotubes and buckyballs at ambient and high temperature, (3) a diverse set of aluminum configurations including surfaces, compressed and expanded lattices, point defects, grain boundaries, liquids, nanoparticles, all at nonzero temperatures, and (4) eleven niobium oxide crystal phases generated with ab initio molecular dynamics. We compare our proposed method to existing, state-of-the-art methods for the cases of aluminum and niobium oxide. Our order parameter uniquely classifies every configuration and outperforms all studied existing methods, opening the door for its use in a multitude of complex application spaces that can require fine structure-level characterization of atomistic graphs.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Frenkel excitons in heat-stressed supramolecular nanocomposites enabled by tunable cage-like scaffolding

Delocalized Frenkel excitons—coherently shared excitations among chromophores—are responsible for the remarkable efficiency of supramolecular light-harvesting assemblies within photosynthetic organisms. The translation of nature’s design principles to applications in optoelectronic devices has been limited by the fragility of the supramolecular structures used and the delicate nature of Frenkel excitons, particularly under mildly changing solvent conditions and elevated temperatures and upon deposition onto solid substrates. Here, we overcome those functionalization barriers through composition of stable supramolecular light-harvesting nanotubes enabled by tunable (~4.3–4.9 nm), uniform (±0.3 nm) cage-like scaffolds. High-resolution cryogenic electron microscopy, combined with scanning electron microscopy, broadband femtosecond transient absorption spectroscopy and near-field scanning optical microscopy revealed that excitons within the cage-like scaffolds are robust, even under extreme heat stress, and control over nanocomposite dimensions is maintained on solid substrates. Our bio-inspired nanocomposites provide a general framework for the development of next-generation organic devices made from stable supramolecular materials.

14 SOLAR ENERGY↗
DOE OSTI2020

What atoms do when they get together

How atoms organize during the earliest stages of nucleation has been a subject of speculation for over a century. Using atomically resolved electron microscopy, the formation and ordering of metal clusters from individual atoms has now been observed in carbon nanotubes that serve as ‘test tubes’.

De Yoreo, James J.↗
DOE OSTI2023

Nonlinear nanomechanical resonators approaching the quantum ground state

It is an open question whether mechanical resonators can be made nonlinear with vibrations approaching the quantum ground state. This requires the engineering of a mechanical nonlinearity far beyond what has been realized so far. Here we discover a mechanism to boost the Duffing nonlinearity by coupling the vibrations of a nanotube resonator to single-electron tunnelling and by operating the system in the ultrastrong-coupling regime. We find that thermal vibrations become highly nonlinear when lowering the temperature. The average vibration amplitude at the lowest temperature is 13 times the zero-point motion, with approximately 42% of the thermal energy stored in the anharmonic part of the potential. Our work may enable the realization of mechanical Schrödinger cat states, mechanical qubits and quantum simulators emulating the electron–phonon coupling.

36 MATERIALS SCIENCE↗
DOE OSTI2022

On the mechanism of performance improvement of electroactive polyvinyl chloride (PVC) gel actuators via conductive fillers

Abstract The electromechanical actuation of transparent plasticized polyvinyl chloride (PVC) gels with conductive fillers were studied. The effects of functionalized carbon nanotubes (CNTs) and 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF 4 ) ionic liquid (IL) on both the electrical conduction and dielectric processes within PVC gels were investigated, and the differences between the two were clarified. Both CNTs and IL were shown to increase the conductivity of the gels and produce larger electromechanical transduction of a contraction actuator, but only CNTs were shown to increase the electrostatic adhesion force of the PVC gels. The addition of charge carriers to the gel via the inclusion of ILs was shown to significantly reduce the conductivity relaxation time, and the transient current upon voltage polarity reversal indicated multiple peaks corresponding to the introduction of carriers with different polarities and mobilities into the gel. This is believed to cause a screening effect, reducing the charge accumulation at the anode that is the foundational basis for PVC gels’ actuation mechanism. A recommendation for preferable conductive fillers for various applications is made.

36 MATERIALS SCIENCE↗
DOE OSTI2020

A native oxide high-κ gate dielectric for two-dimensional electronics

Silicon-based transistors are approaching their physical limits and thus new high-mobility semiconductors are sought to replace silicon in the microelectronics industry. Both bulk materials (such as silicon-germanium and III–V semiconductors) and low-dimensional nanomaterials (such as one-dimensional carbon nanotubes and two-dimensional transition metal dichalcogenides) have been explored, but, unlike silicon, which uses silicon dioxide (SiO 2 ) as its gate dielectric, these materials suffer from the absence of a high-quality native oxide as a dielectric counterpart. This can lead to compatibility problems in practical devices. Here, we show that an atomically thin gate dielectric of bismuth selenite (Bi 2 SeO 5 ) can be conformally formed via layer-by-layer oxidization of an underlying high-mobility two-dimensional semiconductor, Bi 2 O 2 Se. Using this native oxide dielectric, high-performance Bi 2 O 2 Se field-effect transistors can be created, as well as inverter circuits that exhibit a large voltage gain (as high as 150). The high dielectric constant (~21) of Bi 2 SeO 5 allows its equivalent oxide thickness to be reduced to 0.9 nm while maintaining a gate leakage lower than thermal SiO 2 . The Bi 2 SeO 5 can also be selectively etched away by a wet chemical method that leaves the mobility of the underlying Bi 2 O 2 Se semiconductor almost unchanged.

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

Nano-layer deposition of metal oxides via a condensed water film

Abstract Nanocoatings on solids can be achieved by various processes, including sol-gel and atomic layer deposition. However, challenges remain for achieving uniform nanocoatings on nanoscale substrates at a large scale. Here, we report a versatile and fundamentally different technique, termed condensed layer deposition, for depositing conformal metal oxide nanocoatings on nanoparticles and nanofibers. This approach involves water in liquid hydrocarbons condensing as a nanoscale water film on the substrate surface, enabled by interfacial tension between polar water and nonpolar liquid hydrocarbons. Chemical precursors are then added, which react with the condensed water film to form a metal oxide nanocoating. We demonstrate this for titania, alumina, and niobia on substrates including carbon nanotubes, iron oxide particles and carbon black. Condensed layer deposition can achieve oxide nanocoatings on a variety of substrates with tunable thickness, in one pass, at room temperature.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Photoinduced charge transfer in transition metal dichalcogenide heterojunctions – towards next generation energy technologies

Increasing interest in using two-dimensional transition metal dichalcogenides (2D TMDCs) in optical energy conversion technologies creates a demand for improving the yields and lifetimes of photogenerated charge carriers. Despite inherently fast photocarrier decay in neat 2D TMDCs, the unique photophysics in these quantum-confined systems motivates continued effort to control the evolution of photoexcited states and create functional devices. Here, an intriguing strategy to accomplish this goal is to employ TMDCs in heterojunctions with appropriate semiconductors, where energy level offsets drive photoinduced charge transfer (PCT) across material interfaces. PCT in TMDC-based systems can be optimized for many different applications, such as driving free carriers to photocatalytic sites for redox reactions like water splitting, extracting charge to perform work in photovoltaics or photodetectors, and manipulating the spin and momentum valley electronic degrees of freedom for quantum computing systems. Here, we review recent strides in optimizing PCT for such applications through greater fundamental understanding of the photophysics that occurs at TMDC/semiconductor interfaces. After giving an overview of isolated TMDC properties, synthetic methods, and the basics of PCT, we discuss TMDCs in heterojunctions with several classes of materials, including other TMDCs, small molecule semiconductors, polymers, single-walled carbon nanotubes, quantum dots, perovskites, and electrolytes. In addition to highlighting the unique benefits of each materials category, we also identify parallels across common themes, such as the roles of charge-transfer states, spin, electronic coupling, delocalization, interfacial atomic morphology, and the precise design of energy landscapes to direct charge and energy motion. We hope to capture a broad range of the valuable work in this fast-paced field to inspire new research directions for employing PCT in targeted TMDC-based systems.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2021

High-performance ammonia oxidation catalysts for anion-exchange membrane direct ammonia fuel cells

Low-temperature direct ammonia fuel cells (DAFCs) use carbon-neutral ammonia as a fuel, which has attracted increasing attention recently due to ammonia's low source-to-tank energy cost, easy transport and storage, and wide availability. However, current DAFC technologies are greatly limited by the kinetically sluggish ammonia oxidation reaction (AOR) at the anode. Herein, we report an AOR catalyst, in which ternary PtIrZn nanoparticles with an average size of 2.3 ± 0.2 nm were highly dispersed on a binary composite support comprising cerium oxide (CeO 2 ) and zeolitic imidazolate framework-8 (ZIF-8)-derived carbon (PtIrZn/CeO 2 -ZIF-8) through a sonochemical-assisted synthesis method. Additionally, the PtIrZn alloy, with the aid of abundant OH ad provided by CeO 2 and uniform particle dispersibility contributed by porous ZIF-8 carbon (surface area: ~600 m 2 g -1 ), has shown highly efficient catalytic activity for the AOR in alkaline media, superior to that of commercial PtIr/C. The rotating disk electrode (RDE) results indicate a lower onset potential (0.35 vs. 0.43 V), relative to the reversible hydrogen electrode at room temperature, and a decreased activation energy (~36.7 vs. 50.8 kJ mol -1 ) relative to the PtIr/C catalyst. Notably, the PtIrZn/CeO 2 -ZIF-8 catalyst was assembled with a high-performance hydroxide anion-exchange membrane to fabricate an alkaline DAFC, reaching a peak power density of 91 mW cm -2 . Unlike in aqueous electrolytes, supports play a critical role in improving uniform ionomer distribution and mass transport in the anode. PtIrZn nanoparticles on silicon dioxide (SiO 2 ) integrated with carboxyl-functionalized carbon nanotubes (CNT–COOH) were further studied as the anode in a DAFC. A significantly enhanced peak power density of 314 mW cm -2 was achieved. Density functional theory calculations elucidated that Zn atoms in the PtIr alloy can reduce the theoretical limiting potential of *NH 2 dehydrogenation to *NH by ~0.1 V, which can be attributed to a Zn-modulated upshift of the Pt–Ir d-band that facilitates the N–H bond breakage.

25 ENERGY STORAGE↗
DOE OSTI2021

Static adhesion hysteresis in elastic structures

Adhesive interactions between elastic structures such as graphene sheets, carbon nanotubes, and microtubules have been shown to exhibit hysteresis due to irrecoverable energy loss associated with bond breakage, even in static (rate-independent) experiments. To understand this phenomenon, we start with a minimal theory for the peeling of a thin sheet from a substrate, coupling the local event of bond breaking to the nonlocal elastic relaxation of the sheet and show that this can drive static adhesion hysteresis over a bonding/debonding cycle. Using this model we quantify hysteresis in terms of the adhesion and elasticity parameters of the system. We find that this allows us to derive a scaling relation that preserves hysteresis at different levels of granularity while resolving a seeming paradox of lattice trapping in the continuum limit of a discrete fracture process. Finally, to verify our theory, we use new experiments to demonstrate and measure adhesion hysteresis in bundled microtubules.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Exciton-vibrational dynamics induces efficient self-trapping in a substituted nanoring

Cycloparaphenylenes, being the smallest segments of carbon nanotubes, have emerged as prototypes of the simplest carbon nanohoops. Their unique structure–dynamics–optical properties relationships have motivated a wide variety of synthesis of new related nanohoop species. Studies of how chemical changes, introduced in these new materials, lead to systems with new structural, dynamics and optical properties, expand their functionalities for optoelectronics applications. Herein, we study the effect that conjugation extension of a cycloparaphenylene through the introduction of a satellite tetraphenyl substitution has on its structural and dynamical properties. Our non-adiabatic excited state molecular dynamics simulations suggest that this substitution accelerates the electronic relaxation from the high-energy band to the lowest excited state. This is partially due to efficient conjugation achieved between specific phenyl units as introduced by the tetraphenyl substitution. We observe a particular exciton redistribution during relaxation, in which the tetraphenyl substitution plays a significant role. As a result, an efficient inter-band energy transfer takes place. Besides, the observed phonon-exciton interplay induces a significant exciton self-trapping. Finally, our results encourage and guide the future studies of new phenyl substitutions in carbon nanorings with desired optoelectronic properties.

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

Selective heterogeneous capture and release of actinides using carborane-functionalized electrodes

Here we report the heterogenization of molecular, electrochemically switchable ortho-substituted carboranes ( PO Cb, PO Cb-Pyr) for selective metal capture. Films of PO Cb and PO Cb-Pyr on glassy carbon and carbon fiber (CF) electrodes demonstrated heterogeneous electrochemical behaviour that was enhanced by the inclusion of single-walled carbon nanotubes (CNTs). Galvanostatically charged CF|CNT| PO Cb and CF|CNT| PO Cb-Pyr electrodes selectively captured and released actinides (Th 4+ , UO 2 2+ ) from mixed solutions containing alkali (Cs + ), lanthanide (Nd 3+ , Sm 3+ ) and actinide (Th 4+ , UO 2 2+ ) metal ions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗