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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Nanoparticle/Polyelectrolyte Complexes for Biomimetic Constructs

Abstract Constructing all‐aqueous systems with tailored geometries can generate a new class of biomimetic materials, a fascinating but challenging goal to achieve. Here, by taking advantage of the interfacial complexation of a polyelectrolyte (PE) and cellulose nanocrystals (CNCs), a unique interfacial PE/CNC complex is demonstrated for the stabilization of aqueous two‐phase systems and for the fabrication of all‐aqueous double emulsions and 3D constructs. The thickness of PE/CNC complex can be effectively adjusted by tuning the osmotic stress imbalance between the two aqueous phases and, during the formation and thickening of PE/CNC complex, individual assemblies can be connected to design hierarchical all‐aqueous structures. This new platform affords tremendous potential for engineering biomimetic constructs with advanced functionality, that can be used for chemical separation, delivery, and biphasic cascading reaction vessels.

Yin, Yixuan↗
DOE OSTI2022

Vapor–Fed Electrolyzers for Carbon Dioxide Reduction Using Tandem Electrocatalysts: Cuprous Oxide Coupled with Nickel–Coordinated Nitrogen–Doped Carbon

We report ethylene is particularly attractive due to its major importance as a feedstock for various applications including the polymer industry. As such, catalyst and electrolyzer developments are crucial to achieve industrially relevant ethylene production and efficiency levels. In this work, a tandem electrocatalyst composed of copper nanocubes and nickel-coordinated nitrogen-doped carbon (NiNC) is presented, which is integrated into gas diffusion electrodes (GDEs) for direct conversion of vapor-fed CO 2 into ethylene. Evaluation of tandem GDEs in the vapor-fed flow electrolyzer shows significantly increased ethylene selectivity in terms of faradaic efficiency and C 2 H 4 /CO ratio compared to a non-tandem copper GDE. The enhancements are attributed to the increased local CO availability near the copper surface via effective CO 2 to CO conversion on neighboring NiNC. The experimental results are validated by 3D resolved continuum simulations, which show increased flux of higher-order prod-ucts with the added CO flux from NiNC. The practical viability of Cu/NiNC catalyst is further evaluated in a membrane electrode assembly electrolyzer, achieving 40% FE toward ethylene at 150 mA cm -2 and 3.2 V. These find-ings highlight the high selectivity and formation rate of ethylene achieved by successful device integration of the Cu/NiNC catalyst, demonstrating the potential for implementation in large-scale sustainable CO 2 electrolyzers.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Shape-Controlled NaTaO 3 by Flux-Mediated Synthesis

NaTaO 3 is a stable and wide bandgap n-type semiconductor material with many different applications. Here, a flux-mediated synthesis method is presented for NaTaO 3 resulting in highly distinctive, substrate covering shapes via precursor chemistry variation at comparatively low temperatures. It is found that the microstructure of the resulting NaTaO 3 films can be varied from nanocubes to smooth thin films. These shapes and surface chemistries can be correlated by employing density functional theory calculations and surface sensitive X-ray photoemission spectroscopy. This study provides guidance on how to synthesize the material and tailor its shape and surface termination for different applications. Finally, as a proof of concept of one possible application, NaTaO 3 is applied to perovskite solar cells as the electron transport layer, resulting in conversion efficiencies of >19%. Further, this study provides a new strategy for designing ternary oxide thin films for renewable energy applications.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2022

Enabling Conversion-Type Iron Fluoride Cathode by Halide-Based Solid Electrolyte

The practical application of low-cost and energy-dense iron fluoride cathodes has been hindered by the first cycle electrochemical irreversibility, cycling instability, and large voltage hysteresis. Here, we report that these challenges may be overcome by the utilization of halide-based solid electrolytes (SEs). The excellent electrochemical stability of halide-based SEs enables a complete conversion and deconversion of FeF 2 which cannot be achieved with sulfide-based SEs. Due to restricted and reversible decomposition of SE, prevention of Fe dissolution, mechanical confinement of active material, as well as improved electrode kinetics, solid-state FeF 2 cathode with halide-based SE demonstrated superior electrochemical performance compared with FeF 2 electrodes in liquid electrolytes, with a high 1st cycle coulombic efficiency (~100 %), high specific capacity (~600 mAh/g), long cycle life (>100 cycles) and high-rate performance (up to 2C). In conclusion, our results suggest solidifying the batteries may be a viable approach to addressing the long-standing key challenges of iron fluoride cathodes.

25 ENERGY STORAGE↗
DOE OSTI2022

High Current-Density-Charging Lithium Metal Batteries Enabled by Double-Layer Protected Lithium Metal Anode

The practical application of lithium (Li) metal anode (LMA) is still hindered by non-uniformity of solid electrolyte interphase (SEI), formation of "dead" Li, and continuous consumption of electrolyte although LMA has an ultrahigh theoretical specific capacity and a very low electrochemical redox potential. Herein, we report a facile protection strategy for LMA using a double layer (DL) coating that consists of a polyethylene oxide (PEO)-based bottom layer which is highly stable with LMA and promotes uniform ion flux, and a cross-linked polymer-based top layer which prevents solvation of PEO layer in electrolytes. Li deposited on DL-coated Li (DL@Li) exhibits a smoother surface and much larger size than that deposited on bare Li. The LiF/Li 2 O enriched SEI layer generated by the salt decomposition on top of DL@Li further suppresses the side reactions between Li and electrolyte. Driven by the abovementioned advantageous features, the DL@Li||LiNi 0.6 Mn 0.2 Co 0.2 O 2 cells demonstrate capacity retention of 92.4% after 220 cycles at a current density of 2.1 mA cm -2 (C/2 rate) and stability at a high charging current density of 6.9 mA cm -2 (1.5C rate). These results indicate that the DL protection is promising to overcome the rate limitation of LMAs and high energy-density Li metal batteries.

25 ENERGY STORAGE↗
DOE OSTI2023

Multimodal Characterization of Crystal Structure and Formation in Rubrene Thin Films Reveals Erasure of Orientational Discontinuities

Abstract Multimodal multiscale characterization provide opportunities to study organic semiconducting thin films with multiple length scales, across multiple platforms, to elucidate crystallization mechanisms of the various microstructures that impact functionality. With polarized scanning transmission X‐ray and 4D‐scanning transmission electron microscopy, hybrid crystalline structures in rubrene thin films in which large crystalline domains surround a common nucleus and transition to a spherulite morphology at larger radii is observed. These high‐resolution techniques reveal how azimuthal orientational discontinuities at smaller radii are erased as spherulite morphology takes hold. In situ crystallization in the films with optical microscopy is also captured, discovering the importance of considering the initial temperature increase of a film during thermal annealing over the crystallization timescale. This kinetic information of the radial crystallization rate and of corresponding film heating kinetics is used to estimate the temperature at which the larger crystalline regions transition into a spherulite. By combining the results obtained from the different characterization modes, it is learned that thermal conditions can sensitively affect the crystallization of rubrene and other organic thin films. The observations suggest opportunities for more complex temperature‐dependent processing to maximize hybrid structures’ functionality in organic thin films and demonstrate that multimodal studies deepen the understanding of structure‐function dynamics.

Tan, Jenna A.↗
DOE OSTI2023

A Materials Perspective on Direct Recycling of Lithium-Ion Batteries: Principles, Challenges and Opportunities

As the dominant means of energy storage technology today, the widespread deployment of lithium-ion batteries (LIBs) would inevitably generate countless spent batteries at their end of life. From the perspectives of environmental protection and resource sustainability, recycling is a necessary strategy to manage end-of-life LIBs. Compared with traditional hydrometallurgical and pyrometallurgical recycling methods, the emerging direct recycling technology, rejuvenating spent electrode materials via a non-destructive way, has attracted rising attention due to its energy efficient processes along with increased economic return and reduced CO 2 footprint. This review investigates the state-of-the-art direct recycling technologies based on effective relithiation through solid-state, aqueous, eutectic solution and ionic liquid mediums and thoroughly discusses the underlying regeneration mechanism of each method regarding different battery chemistries. It is concluded that direct regeneration can be a more energy-efficient, cost-effective, and sustainable way to recycle spent LIBs compared with traditional approaches. Additionally, it is also identified that the direct recycling technology is still in its infancy with several fundamental and technological hurdles such as efficient separation, binder removal and electrolyte recovery. Finally, in addressing these remaining challenges, this review proposes an outlook on potential technical avenues to accelerate the development of direct recycling toward industrial applications.

25 ENERGY STORAGE↗
DOE OSTI2023

Fe-N 4 O-C Nanoplates Covalently Bonding on Graphene for Efficient CO 2 Electroreduction and Zn-CO 2 Batteries

Electrochemical carbon dioxide (CO 2 ) reduction into value-added products holds great promise in moving toward carbon neutrality but remains a grand challenge due to lack of efficient electrocatalysts. Herein, the nucleophilic substitution reaction is elaborately harnessed to synthesize carbon nanoplates with a Fe-N 4 O configuration anchored onto graphene substrate (Fe-N 4 O-C/Gr) through covalent linkages. Density functional theory calculations demonstrate the unique configuration of Fe-N 4 O with one oxygen (O) atom in the axial direction not only suppresses the competing hydrogen evolution reaction, but also facilitates the desorption of *CO intermediate compared with the commonly planar single-atomic Fe sites. The Fe-N 4 O-C/Gr shows excellent performance in the electroreduction of CO 2 into carbon monoxide (CO) with an impressive Faradaic efficiency of 98.3% at -0.7 V versus reversible hydrogen electrode (RHE) and a high turnover frequency of 3511 h -1 . Furthermore, as a cathode catalyst in an aqueous zinc (Zn)-CO 2 battery, the Fe-N 4 O-C/Gr achieves a high CO Faradaic efficiency (≈91%) at a discharge current density of 3 mA cm -2 and long-term stability over 74 h. Here this work opens up a new route to simultaneously modulate the geometric and electronic structure of single-atomic catalysts toward efficient CO 2 conversion.

25 ENERGY STORAGE↗
DOE OSTI2023

Critical Roles of Chalcogenide Anion on Strengthening Stability of Ni 2 Mo 6 Te 8 for Almost Exclusive Electrocatalysts Nitrate to Ammonia Conversion

Electrochemical hydrogenation of nitrate to ammonia using renewable electricity is a promising route for sustainability but lacks catalysts that can deliver balanced selectivity, activity, and durability. For this work, a new family of noble metal-free and high-performing Chevrel phase Ni 2 Mo 6 T 8 (T = S, Se, and Te) catalysts that have similar structural and textural properties and differ presumably only in chalcogenide anion is systematically studied. The side-by-side comparisons allow the uncovering of the critical roles of chalcogenide anions in impacting kinetic activities and long-term durability. The incorporation of anions with larger size and smaller electronegativity from sulfide to selenide and telluride invokes stronger inhibition of the otherwise competing hydrogen evolution reaction (HER) and steers the hydrogenation toward the selective formation of ammonia, thus improving both Faradic selectivity and the turnover frequency to high levels of 99.4% and 21.5 s –1 , respectively, on the Ni 2 Mo 6 Te 8 catalyst. More significantly, the bulkier anion in the Ni 2 Mo 6 T 8 catalyst kinetically inhibited the intercalation of electrolyte cations, a major degradation mechanism in the catalyst family examined here and delivered several times improved durability. Therefore, this study introduces novel active motifs for selective nitrate reduction and provides insights into the catalyst degradation mechanism and practical ways to improve durability.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Efficient and Photostable Organic Solar Cells Achieved by Alloyed Dimer Acceptors with Tailored Linker Structures

Abstract High power conversion efficiency (PCE) and long‐term stability are prerequisites for commercialization of organic solar cells (OSCs). Herein, two dimer acceptors (DYTVT and DYTCVT) are developed with different properties through linker engineering, and study their effects as alloy‐like acceptors on the photovoltaic performance and photostability of OSCs. These ternary OSCs effectively combine the advantages of both dimer acceptors. DYTVT, characterized by its high backbone planarity, ensures elevated electron mobility and high glass‐transition temperature (T g ), leading to efficient charge transport and enhanced photostability of OSCs. Conversely, DYTCVT, with its significant dipole moment and electrostatic potential, enhances compatibility of the alloy acceptors with donors and refines the blend morphology, facilitating efficient charge generation in OSCs. Consequently, D18:DYTVT:DYTCVT OSCs exhibit higher PCE (18.4%) compared to D18:MYT (monomer acceptor, PCE = 16.5%), D18:DYTVT (PCE = 17.4%), and D18:DYTCVT (PCE = 17.0%) OSCs. Furthermore, owing to higherT g of alloy acceptors (133 °C) than MYT (T g = 80 °C) and DYTCVT (T g = 120 °C), D18:DYTVT:DYTCVT OSCs have significantly higher photostability (t 80% lifetime = 4250 h under 1‐sun illumination) compared to D18:MYT (t 80% lifetime = 40 h) and D18:DYTCVT OSCs (t 80% lifetime = 2910 h).

Chemistry↗
DOE OSTI2024

Impact of Linker Engineering in Core‐Linked Dimeric Acceptors for High‐Performance Organic Solar Cells

Abstract The dimerization of small molecule acceptors (SMAs) is a promising strategy for enhancing the long‐term stability and power conversion efficiency (PCE) of organic solar cells (OSCs). However, the reported DSMAs are primarily limited to end‐linked molecular configurations, highlighting the need for further exploration of various dimer architectures. Herein, the development of two distinct core‐linked dimerized SMAs (DYF‐V and DYF‐E) are reported with tailored linker structures (vinylene and ethynyl, respectively), achieving high‐performance OSCs (PCE = 18.53%). Interestingly, a subtle change in the linker structures results in markedly different molecular properties and photovoltaic performances of the dimer acceptors. DYF‐E with an ethynyl linker exhibits more twisted backbone conformation and mitigated aggregation property compared to DYF‐V, inducing desirable blend morphologies with a polymer donor including high crystallinity, face‐on oriented packing structures, and well‐intermixed domains. Thus, the DYF‐E‐based OSCs exhibit a high PCE (17.02%), which significantly outperforms the DYF‐V‐based OSCs (PCE = 9.98%). Furthermore, the ternary OSCs based on DYF‐E achieve a higher PCE of 18.53%. Thus, this study highlights the significance of selecting an appropriate linker in core‐linked dimerized SMAs for producing high‐performance OSCs.

Oh, Shinbee↗
DOE OSTI2024

In Situ Cyclized Polyacrylonitrile Coating: Key to Stabilizing Porous High-Entropy Oxide Anodes for High-Performance Lithium-Ion Batteries

High-entropy oxides (HEOs) composed of multiple metal elements have attracted great attention as anode materials for lithium-ion batteries (LIBs) due to the synergistic effects of various metal species. However, the practical applications of HEOs are still plagued by poor conductivity, unstable solid electrolyte interphase (SEI) and poor cycling stability. In this work, nanosized (FeCoNiCrMn) 3 O 4 HEO (NHEO) is prepared successfully by the NaCl-assisted mechanical ball-milling strategy. Novelly, polyacrylonitrile (PAN) is used as the binder and then in situ thermochemically cyclized to construct a cyclized PAN (cPAN) outer layer onto NHEO (NHEO-cPAN). The in situ formed cPAN coating not only improves the electrical conductivity, but also reinforces the structural and interfacial stability, and thereby, the resulted NHEO-cPAN electrode exhibits significantly enhanced rate and cyclic performance. Specifically, NHEO-PAN500 electrode delivers a high reversible capacity of 560 mAh g –1 at 5 A g –1 and a high-capacity retention of 83% over 800 cycles at 3 A g –1 . Furthermore, the structural evolution and electrochemical behavior of NHEO-PAN electrode during discharge/charge is systematically investigated by operando X-ray diffraction, in situ impedance spectroscopy and ex situ high-resolution transmission electron microscopy. Therefore, this work provides new insights into the engineering of electrode and interphase for high-performance HEO electrode materials, potentially enlightening the practical applications of HEO-based LIBs.

25 ENERGY STORAGE↗
DOE OSTI2025

Large Anomalous and Topological Hall Effect and Nernst Effect in a Dirac Kagome Magnet Fe 3 Ge

Searching for Kagome magnets with novel magnetic and electronic properties has been attracting significant efforts recently. Here, the magnetic, electronic, and thermoelectric properties of Fe 3 Ge single crystals with Fe atoms forming a slightly distorted Kagome lattice are reported. It is shown that Fe 3 Ge exhibits a large anomalous Hall effect and anomalous Nernst effect. The observed anomalous transverse thermoelectric conductivity $|α^A_{xz}|$ reaches ≈4.6 A m −1 K −1 , which is larger than the conventional ferromagnets and most of the topological ferromagnets reported in literature. The first-principles calculations suggest that these exceptional transport properties are dominated by the intrinsic mechanism, which highlights the significant contribution of the Berry curvature of massive Dirac gaps in the momentum space. Additionally, a topological Hall resistivity of 0.9 µΩ cm and a topological Nernst coefficient of 1.2 µV K −1 are also observed, which are presumably ascribed to the Berry phase associated with the field-induced non-zero scalar spin chirality. These features highlight the synergic effects of the Berry phases in both momentum space and real space of Fe 3 Ge, which render it an excellent candidate for room-temperature thermoelectric applications based on transverse transport.

Kagome magnet↗
DOE OSTI2023

Preparation of 2D Polyaniline/MoO 3– x Superlattice Nanosheets via Intercalation-Induced Morphological Transformation for Efficient Chemodynamic Therapy

Organic intercalation of layered nanomaterials is an attractive strategy to fabricate organic/inorganic superlattices for a wide range of promising applications. However, the synthesis of 2D organic/inorganic superlattice nanosheets remains a big challenge. In this work, the preparation of 2D polyaniline/MoO 3–x (PANI/MoO 3–x ) superlattice nanosheets via intercalation-induced morphological transformation from MoO 3 nanobelts, as efficient Fenton-like reagents for chemodynamic therapy (CDT), is reported. Micrometer-long MoO 3 nanobelts are co-intercalated with Na + /H 2 O followed by the guest exchange with aniline monomer for in situ polymerization to obtain PANI/MoO 3–x nanosheets. Intriguingly, the PANI intercalation can induce the morphological transformation from long MoO 3 nanobelts to 2D PANI/MoO 3–x nanosheets along with the partial reduction of Mo 6+ to Mo 5+ , and generation of rich oxygen vacancies. More importantly, thanks to the PANI intercalation-induced activation, the PANI/MoO 3–x nanosheets exhibit excellent Fenton-like catalytic activity for generation of hydroxyl radical (·OH) by decomposing H 2 O 2 compared with the MoO 3 nanobelts. It is speculated that the good conductivity of PANI can facilitate electron transport during the Fenton-like reaction, thereby enhancing the efficiency of CDT. Thus, the polyvinylpyrrolidone-modified PANI/MoO 3–x nanosheets can function as Fenton-like reagents for highly efficient CDT to kill cancer cells and eradicate tumors.

2D materials↗
DOE OSTI2020

Steric Impediment of Ion Migration Contributes to Improved Operational Stability of Perovskite Solar Cells

The operational instability of perovskite solar cells (PSCs) is understood to mainly originate from the migration of ionic species (or charged defects) under a potential gradient. Compositional engineering of the “A” site cation of the ABX3 perovskite structure has been shown to be an effective route to improve the stability of PSCs. Here, the effect of size-mismatch-induced lattice distortions on the ion migration energetics and operational stability of PSCs is investigated. It is determined that the size mismatch of the mixed “A” site composition films and devices leads to a steric effect to impede the migration pathways of ions to increase the activation energy of ion migration, which is demonstrated through multiple theoretical and experimental evidence. Consequently, the mixed composition devices exhibit significantly improved thermal stability under continuous heating at 85 °C and operational stability under continuous 1 sun illumination, with an extrapolated lifetime of 2011 h, compared to the 222 h of the reference device.

14 SOLAR ENERGY↗
DOE OSTI2020

Two‐Dimensional Superstructures of Silica Cages

Abstract Despite extensive studies on mesoporous silica since the early 1990s, the synthesis of two‐dimensional (2D) silica nanostructures remains challenging. Here, mesoporous silica is synthesized at an interface between two immiscible solvents under conditions leading to the formation of 2D superstructures of silica cages, the thinnest mesoporous silica films synthesized to date. Orientational correlations between cage units increase with increasing layer number controlled via pH, while swelling with oil and mixed surfactants increase micelle size dispersity, leading to complex clathrate type structures in multilayer superstructures. The results suggest that a three‐dimensional (3D) crystallographic registry within cage‐like superstructures emerges as a result of the concerted 3D co‐assembly of the organic and inorganic components. Mesoporous 2D superstructures can be fabricated over macroscopic film dimensions and stacked on top of each other. The realization of previously inaccessible mesoporous silica heterostructures with separation or catalytic properties unachievable via conventional bulk syntheses is envisioned.

Aubert, Tangi↗
DOE OSTI2020

Evaporated Se x Te 1-x Thin Films with Tunable Bandgaps for Short-Wave Infrared Photodetectors

Semiconducting absorbers in high-performance short-wave infrared (SWIR) photodetectors and imaging sensor arrays are dominated by single-crystalline germanium and III-V semiconductors. However, these materials require complex growth and device fabrication procedures. In this work, thermally evaporated Se x Te 1- x alloy thin films with tunable bandgaps for the fabrication of high-performance SWIR photodetectors are reported. From absorption measurements, it is shown that the bandgaps of Se x Te 1- x films can be tuned continuously from 0.31 eV (Te) to 1.87 eV (Se). Owing to their tunable bandgaps, the peak responsivity position and photoresponse edge of Se x Te 1- x film-based photoconductors can be tuned in the SWIR regime. By using an optical cavity substrate consisting of Au/Al 2 O 3 to enhance its absorption near the bandgap edge, the Se 0.32 Te 0.68 film (an optical bandgap of ≈0.8 eV)-based photoconductor exhibits a cut-off wavelength at ≈1.7 μm and gives a responsivity of 1.5 AW -1 and implied detectivity of 6.5 × 10 10 cm Hz 1/2 W -1 at 1.55 μm at room temperature. Importantly, the nature of the thermal evaporation process enables the fabrication of Se 0.32 Te 0.68 -based 42 × 42 focal plane arrays with good pixel uniformity, demonstrating the potential of this unique material system used for infrared imaging sensor systems.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Consolidating Lithiothermic-Ready Transition Metals for Li2S-Based Cathodes

Li 2 S holds a promising role as a high-capacity Li-containing cathode, circumventing use of metallic lithium in constructing next-generation batteries to replace current Li-ion batteries. However, progress of Li 2 S cathode has been plagued by its intrinsic drawbacks, including high activation potentials, poor rate performance, and rapid capacity fading during long cycling. In this work, a series of Li 2 S/transition metal (TM) nanocomposites are synthesized via a lithiothermic reduction reaction, and it is realized that the presence of TMs in Li 2 S matrix can transform electrochemical behaviors of Li 2 S. On the one hand, the incorporation of W, Mo, or Ti greatly increases electronic and ionic conductivity of Li 2 S composites and inhibits the polysulfide dissolution via the TM—S bond, effectively addressing the drawbacks of Li 2 S cathodes. In particular, Li 2 S/W and Li 2 S/Mo exhibit the highest ionic conductivity of solid-phase Li-ion conductors ever-reported: 5.44 × 10 –2 and 3.62 × 10 –2 S m –1 , respectively. On the other hand, integrating Co, Mn, and Zn turns Li 2 S into a prelithiation agent, forming metal sulfides rather than S 8 after the full charge. These interesting findings may shed light on the design of Li 2 S-based cathode materials.

25 ENERGY STORAGE↗