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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Enhancing Hydrogen Production from Bioenergy Crops via Photoreforming

Photoreforming perennial bioenergy crops (willow, Miscanthus , and poplar) has the potential to produce H 2 with reduced environmental impacts. To understand the compositional effects of the biomass on the average rate of H 2 production over the first 30 min of reaction ( r H 2 ), the r H 2 values of model biomass component (i.e., cellulose, hemicellulose, and lignin) mixtures were compared with those from the raw biomass. The higher cellulose or hemicellulose content in multicomponent mixtures resulted in higher r H 2 , whereas lignin reduced the hydrogen production rate. However, with raw biomass, the ratio of biomass components alone did not determine the r H 2 via photoreforming, with rates of hydrogen production for different varieties of willow ranging between 1.9 μmol h -1 and 12.3 μmol h -1 , 11.8 μmol h -1 for a poplar, and 6.8 μmol h -1 for a miscanthus biomass. In addition, comparable r H 2 values of raw poplar and its extracted cellulose via an IonoSolv treatment indicated the possibility of using raw biomass materials without delignification for generating H 2 via photoreforming. Importantly, r H 2 was positively correlated with the interaction between water and the biomass, as assessed by NMR relaxation via an examination of the T 1 /T 2 ratio. A stronger water-biomass interaction resulted in a higher r H 2 . Genetic modification of biomass has been suggested as a putative way to improve the r H 2 of biomass with an enhanced interaction with water. This research enhances the understanding of factors influencing H 2 production from lignocellulosic biomass by photoreforming and supports the breeding and management of perennial biomass crops to maximize H 2 yields while minimizing land area requirements.

biomass↗
DOE OSTI2023

Allosteric autoregulation of DNA binding via a DNA-mimicking protein domain: a biophysical study of ZNF410–DNA interaction using small angle X-ray scattering

ZNF410 is a highly-conserved transcription factor, remarkable in that it recognizes a 15-base pair DNA element but has just a single responsive target gene in mammalian erythroid cells. ZNF410 includes a tandem array of five zinc-fingers (ZFs), surrounded by uncharacterized N- and C-terminal regions. Unexpectedly, full-length ZNF410 has reduced DNA binding affinity, compared to that of the isolated DNA binding ZF array, both in vitro and in cells. AlphaFold predicts a partially-folded N-terminal subdomain that includes a 30-residue long helix, preceded by a hairpin loop rich in acidic (aspartate/glutamate) and serine/threonine residues. This hairpin loop is predicted by AlphaFold to lie against the DNA binding interface of the ZF array. In solution, ZNF410 is a monomer and binds to DNA with 1:1 stoichiometry. Surprisingly, the single best-fit model for the experimental small angle X-ray scattering profile, in the absence of DNA, is the original AlphaFold model with the N-terminal long-helix and the hairpin loop occupying the ZF DNA binding surface. For DNA binding, the hairpin loop presumably must be displaced. After combining biophysical, biochemical, bioinformatic and artificial intelligence-based AlphaFold analyses, we suggest that the hairpin loop mimics the structure and electrostatics of DNA, and provides an additional mechanism, supplementary to sequence specificity, of regulating ZNF410 DNA binding.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Chiral kinetic theory of anomalous transport induced by torsion

In Weyl semimetals subjected to torsion, there are two different kinds of chirality: (i) The (coordinate-space) shape of the twisted crystal is chiral and (ii) the momentum space contains chiral quasiparticles. Here we construct a general kinetic theory of anomalous transport using the phase space (coordinate and momentum spaces combined) Berry curvature induced by torsion in Weyl systems. We describe how torsion generates the chiral chemical potential and thus leads to the chiral magnetic effect (CME) in the presence of a background magnetic field. We propose to measure the CME current induced by the torsion as a way to detect the anomalous coupling between the coordinate-space and momentum-space chiralities.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Unravelling the Role of Electron Acceptors for the Universal Enhancement of Charge Transport in Quinoid-Donor-Acceptor Polymers for High-Performance Transistors

The quinoid-donor-acceptor (Q-D-A) strategy has recently emerged as a promising approach for constructing high mobility semiconducting polymers. In order to fully explore the potential of this strategy in improving the charge transport and elucidating the structure-property-performance relationships in Q-D-A polymers, a series of new polymers with different electron acceptor units and backbone coplanarity have been synthesized and characterized. In this work, all of the resulting Q-D-A polymers exhibit much more planar backbone conformations in comparison to their donor-acceptor (D-A) counterparts. Moreover, organic field-effect transistors based on Q-D-A polymers exhibit excellent effective hole mobilities in a range of 0.44 to 3.35 cm 2 V –1 s –1 , most of which are orders of magnitude higher than those of their corresponding D-A polymers. Notably, the hole mobility of 3.35 cm 2 V –1 s –1 is among the highest for the quinoidal-aromatic polymers characterized by conventional spin-coating methods. Furthermore, the role of electron acceptors in Q-D-A polymers has been comprehensively investigated. Polymers with stronger acceptor units are more inclined to deliver edge-on lamellas, high film crystallinity, small effective hole masses, and decent operational stability. The detailed structure-property-device performance relationship will pave the way toward high performance semiconducting polymers using the potent Q-D-A strategy.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Superhydrophobic Phosphonium Modified Robust 3D Covalent Organic Framework for Preferential Trapping of Charge Dispersed Oxoanionic Pollutants

Abstract Charge dispersed and less hydrophilic anionic pollutants are often difficult to be preferentially captured by common cationic framework materials. A gamma radiation modification approach is employed to anchor a superhydrophobic phosphonium‐containing coating on a robust crystalline 3D covalent organic framework (COF). By regulating the surface hydrophobicity, the prepared 3DCOF‐ g ‐VBPPh 3 Cl is endowed with a strong affinity for charge dispersed and less hydrophilic oxoanions, such as MnO 4 − , TcO 4 − and ReO 4 − , to surmount the Hofmeister bias, which much favors remediation of oxoanionic pollutants in complex aqueous systems. Batch and column experiments with 3DCOF‐g‐VBPPh 3 Cl in both tap water and simulated groundwater are performed, and rapid sequestration is achieved with removal efficacy up to 99.995%, record‐high distribution coefficient of 1.0 × 10 8 mL g −1 , and desirable priority over competing anions such as Cl − , SO 4 2− , HCO 3 − , and NO 3 − , confirming promise for remediation of charge dispersed anionic pollutants. Theoretical calculations reveal a mechanism of preferential capture based on electrostatic and dispersion interaction between charge dispersed anions and 3DCOF‐g‐VBPPh 3 Cl that effectively competes with solvation of the aqueous anions.

Wang, Yue↗
DOE OSTI2023

Zinc‐Imidazolate Films as an All‐Dry Resist Technology

Here, motivated by the drawbacks of solution phase processing, an all‐dry resist formation process is presented that utilizes amorphous zinc‐imidazolate (aZnMIm) films deposited by atomic/molecular layer deposition (ALD/MLD), patterned with electron beam lithography (EBL), and developed by novel low temperature (120 °C) gas phase etching using 1,1,1,5,5,5‐hexafluoroacetylacetone (hfacH) to achieve well‐resolved 22 nm lines with a pitch of 30 nm. The effects of electron beam irradiation on the chemical structure and hfacH etch resistance of aZnMIm films are investigated, and it is found that electron irradiation degrades the 2‐methylimidazolate ligands and transforms aZnMIm into a more dense material that is resistant to etching by hfacH and has a C:N:Zn ratio effectively identical to that of unmodified aZnMIm. These findings showcase the potential for aZnMIm films to function in a dry resist technology. Sensitivity, contrast, and critical dimensions of the patterns are determined to be 37 mC cm −2 , 0.87, and 29 nm, respectively, for aZnMIm deposited on silicon substrates and patterned at 30 keV. This work introduces a new direction for solvent‐free resist processing, offering the prospect of scalable, high‐resolution patterning techniques for advanced semiconductor fabrication processes.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2024

High‐Pressure Synthesis of Ultra‐Incompressible, Hard and Superconducting Tungsten Nitrides

Abstract Transition metal nitrides, particularly those of 5 d metals, are known for their outstanding properties, often relevant for industrial applications. Among these metal elements, tungsten is especially attractive given its low cost. In this high‐pressure investigation of the W–N system, two novel ultra‐incompressible tungsten nitride superconductors, namely W 2 N 3 and W 3 N 5 , are successfully synthesized at 35 and 56 GPa, respectively, through a direct reaction between N 2 and W in laser‐heated diamond anvil cells. Their crystal structure is determined using synchrotron single‐crystal X‐ray diffraction. While the W 2 N 3 solid's sole constituting nitrogen species are N 3‐ units, W 3 N 5 features both discrete N 3‐ as well as N 2 4‐ pernitride anions. The bulk modulus of W 2 N 3 and W 3 N 5 is experimentally determined to be 380(3) and 406(7) GPa, and their ultra‐incompressible behavior is rationalized by their constituting WN 7 polyhedra and their linkages. Importantly, both W 2 N 3 and W 3 N 5 are recoverable to ambient conditions and stable in air. Density functional theory calculations reveal W 2 N 3 and W 3 N 5 to have a Vickers hardness of 30 and 34 GPa, and superconducting transition temperatures at ambient pressure (50 GPa) of 11.6 K (9.8 K) and 9.4 K (7.2 K), respectively. Additionally, transport measurements performed at 50 GPa on W 2 N 3 corroborate with the calculations.

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 OSTI2021

Designing a Zn–Ag Catalyst Matrix and Electrolyzer System for CO 2 Conversion to CO and Beyond

CO 2 emissions can be transformed into high-added-value commodities through CO 2 electrocatalysis; however, efficient low-cost electrocatalysts are needed for global scale-up. Inspired by other emerging technologies, the authors report the development of a gas diffusion electrode containing highly dispersed Ag sites in a low-cost Zn matrix. Here, this catalyst shows unprecedented Ag mass activity for CO production: –614 mA cm –2 at 0.17 mg of Ag. Subsequent electrolyte engineering demonstrates that halide anions can further improve stability and activity of the Zn–Ag catalyst, outperforming pure Ag and Au. Membrane electrode assemblies are constructed and coupled to a microbial process that converts the CO to acetate and ethanol. Combined, these concepts present pathways to design catalysts and systems for CO 2 conversion toward sought-after products.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Topological Crystalline Insulator Candidate ErAsS with Hourglass Fermion and Magnetic-Tuned Topological Phase Transition

Topological crystalline insulators (TCIs) with hourglass fermion surface state have attracted a lot of attention and are further enriched by crystalline symmetries and magnetic order. Here, the emergence of hourglass fermion surface state and exotic phases in the newly discovered, air-stable ErAsS single crystals are shown. In the paramagnetic phase, ErAsS is expected to be a TCI with hourglass fermion surface state protected by the nonsymmorphic symmetry. Dirac-cone-like bands and nearly linear dispersions in large energy range are experimentally observed, consistent well with theoretical calculations. Below T N ≈ 3.27 K, ErAsS enters a collinear antiferromagnetic state, which is a trivial insulator breaking the time-reversal symmetry. An intermediate incommensurate magnetic state appears in a narrow temperature range (3.27–3.65 K), exhibiting an abrupt change in magnetic coupling. Overall, the results reveal that ErAsS is an experimentally available TCI candidate and provide a unique platform to understand the formation of hourglass fermion surface state and explore magnetic-tuned topological phase transitions.

36 MATERIALS SCIENCE↗
DOE OSTI2022

High‐Efficiency Magnon‐Mediated Magnetization Switching in All‐Oxide Heterostructures with Perpendicular Magnetic Anisotropy

Abstract The search for efficient approaches to realize local switching of magnetic moments in spintronic devices has attracted extensive attention. One of the most promising approaches is the electrical manipulation of magnetization through electron‐mediated spin torque. However, the Joule heat generated via electron motion unavoidably causes substantial energy dissipation and potential damage to spintronic devices. Here, all‐oxide heterostructures of SrRuO 3 /NiO/SrIrO 3 are epitaxially grown on SrTiO 3 single‐crystal substrates following the order of the ferromagnetic transition metal oxide SrRuO 3 with perpendicular magnetic anisotropy, insulating and antiferromagnetic NiO, and metallic transition metal oxide SrIrO 3 with strong spin–orbit coupling. It is demonstrated that instead of the electron spin torques, the magnon torques present in the antiferromagnetic NiO layer can directly manipulate the perpendicular magnetization of the ferromagnetic layer. This magnon mechanism may significantly reduce the electron motion‐related energy dissipation from electron‐mediated spin currents. Interestingly, the threshold current density to generate a sufficient magnon current to manipulate the magnetization is one order of magnitude smaller than that in conventional metallic systems. These findings suggest a route for developing highly efficient all‐oxide spintronic devices operated by magnon current.

Zheng, Dongxing↗
DOE OSTI2023

Stabilizing the Deep Sodiation Process in Layered Sodium Manganese Cathodes by Anchoring Boron Ions

Advanced high-energy-density sodium-ion batteries (SIBs) are inseparable from cathode materials with high specific capacities. Layered manganese-rich oxides (Na x MnO 2 , 0.6 ≤ x ≤1) are promising cathode materials owing to their ease of intercalation and extraction of a considerable amount of sodium ions. However, lattice interactions, especially electrostatic repulsive forces and anisotropic stresses, are usually caused by deep desodiatin/sodiation process, resulting in intragranular cracks and capacity degradation in SIBs. Here, boron ions are introduced into the layered structure to build up B-O-Mn bonds. Further, the regulated electronic structure in Na 0.637 B 0.038 MnO 2 (B-NMO) materials inhibits the deformation of MnO 6 octahedra, which finally achieves a gentle structural transition during the deep sodiation process. B-NMO electrode exhibits a high capacity (141 mAh g –1 ) at 1 C with a capacity retention of 81% after 100 cycles. Therefore, anchoring boron to manganese-rich materials inhibits the detrimental structural evolution of deep sodiation and can be used to obtain excellent cathode materials for SIBs.

25 ENERGY STORAGE↗
DOE OSTI2022

Unblocking Oxygen Charge Compensation for Stabilized High‐Voltage Structure in P2‐Type Sodium‐Ion Cathode

Abstract Layered transition‐metal (TM) oxides are ideal hosts for Li + charge carriers largely due to the occurrence of oxygen charge compensation that stabilizes the layered structure at high voltage. Hence, enabling charge compensation in sodium layered oxides is a fascinating task for extending the cycle life of sodium‐ion batteries. Herein a Ti/Mg co‐doping strategy for a model P2‐Na 2/3 Ni 1/3 Mn 2/3 O 2 cathode material is put forward to activate charge compensation through highly hybridized O 2 p TM 3 d covalent bonds. In this way, the interlayer OO electrostatic repulsion is weakened upon deeply charging, which strongly affects the systematic total energy that transforms the striking P2–O2 interlayer contraction into a moderate solid‐solution‐type evolution. Accordingly, the cycling stability of the codoped cathode material is improved superiorly over the pristine sample. This study starts a perspective way of optimizing the sodium layered cathodes by rational structural design coupling electrochemical reactions, which can be extended to widespread battery researches.

25 ENERGY STORAGE↗
DOE OSTI2024

Pathway Evolution Through a Bottlenecking-Debottlenecking Strategy and Machine Learning-Aided Flux Balancing

The evolution of pathway enzymes enhances the biosynthesis of high-value chemicals, crucial for pharmaceutical, and agrochemical applications. However, unpredictable evolutionary landscapes of pathway genes often hinder successful evolution. Here, the presence of complex epistasis is identifued within the representative naringenin biosynthetic pathway enzymes, hampering straightforward directed evolution. Subsequently, a biofoundry-assisted strategy is developed for pathway bottlenecking and debottlenecking, enabling the parallel evolution of all pathway enzymes along a predictable evolutionary trajectory in six weeks. This study then utilizes a machine learning model, ProEnsemble, to further balance the pathway by optimizing the transcription of individual genes. The broad applicability of this strategy is demonstrated by constructing an Escherichia coli chassis with evolved and balanced pathway genes, resulting in 3.65 g L -1 naringenin. The optimized naringenin chassis also demonstrates enhanced production of other flavonoids. This approach can be readily adapted for any given number of enzymes in the specific metabolic pathway, paving the way for automated chassis construction in contemporary biofoundries.

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

Regiospecific Incorporation of Acetylene Linker in High‐Electron Mobility Dimerized Acceptors for Organic Solar Cells with High Efficiency (18.8%) and Long 1‐Sun Lifetime (> 5000 h)

Abstract The commercialization of organic solar cells (OSCs) requires both high power conversion efficiency (PCE) and long‐term stability. However, the lifetime of the OSCs containing small‐molecule acceptors (SMA) should be significantly enhanced. In this study, a series of planarity‐controlled is developed, high electron mobility dimerized SMAs (DSMAs) and realize OSCs with high‐performance (PCE = 18.8%) and high‐stability ( t 80% lifetime = 5380 h under 1‐Sun illumination). An acetylene linker with a planar triple bond is designed for dimerization of SMA units to afford the high backbone planarity necessary to achieve high crystallinity and electron mobility. To further engineer the molecular conformation and electron mobility of the DSMAs, different regioisomers of a Y‐based SMA are dimerized to yield three regioisomerically distinct DSMAs, denoted as DYA‐I, DYA‐IO, and DYA‐O, respectively. It is found that the crystallinity, electron mobility, and glass transition temperature of the DSMAs gradually increase in the order of DYA‐O, DYA‐IO, and DYA‐I, which, in turn, enhance the PCE and device stability of the resulting OSCs; DYA‐O (PCE = 16.45% and t 80% lifetime = 3337 h) < DYA‐IO (PCE = 17.54% and t 80% lifetime = 4255 h) < DYA‐I (PCE = 18.83% and t 80% lifetime = 5380 h).

Chemistry↗