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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Record-Setting Sorbents for Reversible Water Uptake by Systematic Anion Exchanges in Metal–Organic Frameworks

The reversible capture of water vapor at low humidity can enable transformative applications such as atmospheric water harvesting and heat transfer that uses water as a refrigerant, replacing environmentally detrimental hydro- and chloro-fluorocarbons. The driving force for these applications is governed by the relative humidity at which the pores of a porous material fill with water. Here, we demonstrate modulation of the onset of pore-filling in a family of metal-organic frameworks with record water sorption capacities by employing anion exchange. Unexpectedly, the replacement of the structural bridging Cl - with the more hydrophilic anions F - and OH - does not induce porefilling at lower relative humidity, whereas the introduction of the larger Br - results in a substantial shift toward lower relative humidity. We rationalize these results in terms of pore size modifications as well as the water hydrogen bonding structure based on detailed infrared spectroscopic measurements. Fundamentally, our data suggest that, in the presence of strong nucleation sites, the thermodynamic favorability of water pore-filling depends more strongly on the pore diameter and the interface between water in the center of the pore and water bound to the pore walls than the hydrophilicity of the pore wall itself. On the basis of these results, we report two materials that exhibit record water uptake capacities in their respective humidity regions and extended stability over 400 water adsorption-desorption cycles.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Anion transport as a target of adaption to perchlorate in sulfate-reducing communities

Inhibitors can be used to control the functionality of microbial communities by targeting specific metabolisms. The targeted inhibition of dissimilatory sulfate reduction limits the generation of toxic and corrosive hydrogen sulfide across several industrial systems. Sulfate-reducing microorganisms (SRM) are specifically inhibited by sulfate analogs, such as perchlorate. Previously, we showed pure culture SRM adaptation to perchlorate stress through mutation of the sulfate adenylyltransferase, a central enzyme in the sulfate reduction pathway. Here, we explored adaptation to perchlorate across unconstrained SRM on a community scale. We followed natural and bio-augmented sulfidogenic communities through serial transfers in increasing concentrations of perchlorate. Our results demonstrated that perchlorate stress altered community structure by initially selecting for innately more resistant strains. Isolation, whole-genome sequencing, and molecular biology techniques allowed us to define subsequent genetic mechanisms of adaptation that arose across the dominant adapting SRM. Changes in the regulation of divalent anion:sodium symporter family transporters led to increased intracellular sulfate to perchlorate ratios, allowing SRM to escape the effects of competitive inhibition. Thus, in contrast to pure-culture results, SRM in communities cope with perchlorate stress via changes in anion transport and its regulation. Finally, this highlights the value of probing evolutionary questions in an ecological framework, bridging the gap between ecology, evolution, genomics, and physiology.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Stabilization of N6 and N8 anionic units and 2D polynitrogen layers in high-pressure scandium polynitrides

Abstract Nitrogen catenation under high pressure leads to the formation of polynitrogen compounds with potentially unique properties. The exploration of the entire spectrum of poly- and oligo-nitrogen moieties is still in its earliest stages. Here, we report on four novel scandium nitrides, Sc 2 N 6 , Sc 2 N 8 , ScN 5, and Sc 4 N 3 , synthesized by direct reaction between yttrium and nitrogen at 78-125 GPa and 2500 K in laser-heated diamond anvil cells. High-pressure synchrotron single-crystal X-ray diffraction reveals that in the crystal structures of the nitrogen-rich Sc 2 N 6 , Sc 2 N 8, and ScN 5 phases nitrogen is catenated forming previously unknown N 6 6 − and N 8 6 − units and$${\!\,}_{\infty }{\!\,}^{2}({{{{{\rm{N}}}}}}_{5}^{3-})$$ ∞ 2 ( N 5 3 − ) anionic corrugated 2D-polynitrogen layers consisting of fused N 12 rings. Density functional theory calculations, confirming the dynamical stability of the synthesized compounds, show that Sc 2 N 6 and Sc 2 N 8 possess an anion-driven metallicity, while ScN 5 is an indirect semiconductor. Sc 2 N 6 , Sc 2 N 8 , and ScN 5 solids are promising high-energy-density materials with calculated volumetric energy density, detonation velocity, and detonation pressure higher than those of TNT.

Science & Technology - Other Topics↗
DOE OSTI2020

Highly quaternized polystyrene ionomers for high performance anion exchange membrane water electrolysers

Alkaline anion exchange membrane (AEM) electrolysers to produce hydrogen from water remain at an early stage of development, and their performance is far lower than that of systems based on proton exchange membranes. Here, we report an ammonium-enriched anion exchange ionomer that improves the performance of an AEM electrolyser to levels approaching that of state-of-the-art proton exchange membrane electrolysers. Using rotating-disk electrode experiments, we show that a high pH (>13) in the electrode binder is the critical factor for improving the activity of the hydrogen- and oxygen-evolution reactions in AEM electrolysers. Based on this observation, we prepared and tested several quaternized polystyrene electrode binders in an AEM electrolyser. Using the binder with the highest ionic concentration and a NiFe oxygen evolution catalyst, we demonstrated performance of 2.7 A cm -2 at 1.8 V without a corrosive circulating alkaline solution. The limited durability of the AEM electrolyser remains a challenge to be addressed in the future.

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

Achieving a high-performance sodium-ion pouch cell by regulating intergrowth structures in a layered oxide cathode with anionic redox

In P2-type layered transition metal (TM) oxides, which are typical cathode materials for Na-ion batteries, the presence of Li within the TM layer could lead to the formation of specific Na–O–Li configurations that trigger additional oxygen redox at high charging voltages. However, the prismatic-type (P-type) to octahedral-type (O-type) phase transition and irreversible TM migration could be simultaneously aggravated in high state of charge, resulting in structural distortion. Here we demonstrate that excessive desodiation of P2-Na 0.67 Li 0.1 Fe 0.37 Mn 0.53 O 2 (NLFMO) induces the formation of neighbouring O-type stacking faults with an intergrowth structure (that is, interlacing of O- and P-type layers), which leads to out-of-lattice Li migration and irreversible oxygen loss. We show that, by controlling the depth of charge to tailor the intergrowth structure, a P-type stacking state can be uniformly interspersed between the O-type stacking state, thereby avoiding neighbouring O-type stacking faults. Adjusting the O/P intergrowth structure leads to both reversible migration of Li/TM ions and reversible anionic redox in the NLFMO cathode. In conclusion, we thereby achieve a high-performance pouch cell (with an energy density of 165 W h kg −1 based on the entire weight of the cell) with both cationic and anionic redox activities.

25 ENERGY STORAGE↗
DOE OSTI2024

Chemical control of excited-state reactivity of the anionic green fluorescent protein chromophore

Controlling excited-state reactivity is a long-standing challenge in photochemistry, as a desired pathway may be inaccessible or compete with other unwanted channels. An important example is internal conversion of the anionic green fluorescent protein (GFP) chromophore where non-selective progress along two competing torsional modes (P: phenolate and I: imidazolinone) impairs and enables Z-to-E photoisomerization, respectively. Developing strategies to promote photoisomerization could drive new areas of applications of GFP-like proteins. Motivated by the charge-transfer dichotomy of the torsional modes, we explore chemical substitution on the P-ring of the chromophore as a way to control excited-state pathways and improve photoisomerization. As demonstrated by methoxylation, selective P-twisting appears difficult to achieve because the electron-donating potential effects of the substituents are counteracted by inertial effects that directly retard the motion. Conversely, these effects act in concert to promote I-twisting when introducing electron-withdrawing groups. Specifically, 2,3,5-trifluorination leads to both pathway selectivity and a more direct approach to the I-twisted intersection which, in turn, doubles the photoisomerization quantum yield. Our results suggest P-ring engineering as an effective approach to boost photoisomerization of the anionic GFP chromophore.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Halide anion discrimination by a tripodal hydroxylamine ligand in gas and condensed phases

Electrospray ionization of solutions containing a tripodal hydroxylamine ligand, H 3 TriNOx ([((2- t BuNOH)C 6 H 4 CH 2 ) 3 N]) denoted as L, and a hydrogen halide HX: HCl, HBr and/or HI, yielded gas-phase anion complexes [L(X)] - and [L(HX2)] - . Collision induced dissociation (CID) of mixed-halide complexes, [L(HX a X b )] - , indicated highest affinity for I - and lowest for Cl - . Structures and energetics computed by density functional theory are in accord with the CID results, and indicate that the gas-phase binding preference is a manifestation of differing stabilities of the HX molecules. A high halide affinity of [L(H)] + in solution was also demonstrated, though with a highest preference for Cl - and lowest for I - , the opposite observation of, but not in conflict with, what is observed in gas phase. Finally, the results suggest a connection between gas- and condensed-phase chemistry and computational approaches, and shed light on the aggregation and anion recognition properties of hydroxylamine receptors.

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

Iminoguanidines: from anion recognition and separation to carbon capture

Iminoguanidines, first reported in 1898, have received renewed attention in the last 5 years due to their ability to recognize and separate anions from competitive aqueous environments. Iminoguanidines display high recognition abilities towards hydrophilic oxyanions (e.g., sulfate, chromate, carbonate) through strong and complementary hydrogen bonding from the guanidinium groups. Here, this feature article reviews the fundamental anion recognition chemistry of iminoguanidines, as well as real-world applications including sulfate removal from seawater and CO 2 capture for climate change mitigations.

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

Performance and durability of anion exchange membrane water electrolyzers using down-selected polymer electrolytes

Over the last decade, several stable anion exchange polymer electrolytes have been developed for electrochemical devices. Herein, we investigate how chemical structure and physical properties of polymer electrolytes affect performance and durability of anion exchange membrane water electrolyzers (AEMWEs). We select polymer electrolytes with high alkaline stability and consider their polymer properties including conductivity, mechanical/chemical stability, and material interactions to interpret the performance and durability of AEMWEs. Here, the AEMWE with a poly(phenylene) membrane and a poly(fluorene) ionomeric binder exhibited the best performance among those tested in this study; the AEMWE showed ~1 A cm –2 at 2 V under 1 wt% K 2 CO 3 -fed conditions. The voltage degradation rate was 270–550 μV h –1 for several hundred operating hours at a constant current density of 750 mA cm –2 and a differential pressure of 100 pounds per square inch gauge. Based on these results, we discuss research needs of polymer electrolytes for practical AEMWEs.

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

Chlorine gas and anion radical reactivity in molten salts and the link to chlorobasicity

Next-generation nuclear power plants may include exciting novel designs in which molten salts are the coolant or a combination of the coolant and fuel. Whereas it is straightforward to see why having a low volatility coolant can be advantageous for safety, much is not understood about the production of volatile halogen gases as a result of radiation and even less is known about the distribution of these species at and away from interfaces. Using first principles molecular dynamics simulations, we investigate the product of the disproportionation reaction between chlorine anion radicals (nominally Cl 2 ˙ − ) in the bulk and slab configurations. We find that the product depends on the chlorobasicity of the medium. For example, in ZnCl 2 , Cl 2 forms, but in a eutectic mixture of LiCl and KCl, Cl 3 − is formed as a product. We also find that Cl 3 − prefers to form at the vapor interface and this may have implications for corrosion and reactivity. Furthermore, the mechanisms of the mobility of Cl 2 and Cl 3 − are radically different, the first one being vehicular and the second Grotthus-like. Chlorobasicity is linked to the electronic structure of the host melt; ZnCl 2 forms extended networks along which metal ions and anionic counterions have significant electronic orbital overlap forming long, linear, molecular-like constructs; the opposite is true for the alkali metal eutectic salt.

Nguyen, Hung H. [Univ. of Iowa, Iowa City, IA (Uni↗
DOE OSTI2026

NiFeCo-based catalysts in high current zero-gap anion exchange membrane water electrolyzers

Understanding degradation mechanisms in pure water anion exchange membrane water electrolyzers is essential for developing durable and precious metal-free hydrogen production systems, yet electronic, chemical, and transport-driven pathways often occur simultaneously at the anode. To separate these effects, we establish a morphology invariant Ni/Fe/Co thin film model catalyst platform using physical vapor deposition and systematically compare composition-dependent behavior under both pure water and 0.1 M KOH feeds. Devices were operated under industrially relevant current density conditions, galvanostatically at 1 A cm −2 for 24 hours; metal dissolution, ionomer oxidation, and resistance growth were quantified using inductively coupled plasma mass spectrometry, X-ray photoelectron spectroscopy (XPS), and electrochemical impedance spectroscopy. Under pure-water operation, Ni-rich films showed voltage increases that correlated with rising total cell resistance (ΔV ≈ 243 mV, ΔR ≈ 0.17 Ω cm 2 ). Co-rich films maintained near constant voltages with minimal resistance change (ΔV < 10 mV, ΔR ≈ 0.03 Ω cm 2 ) but induced pronounced ionomer oxidation observed by XPS. In 0.1 M KOH, ionomer oxidation is suppressed, and impedance growth is minimized (<0.08 Ω cm 2 ) across all compositions, consistent with reduced transport limitations and improved ionic conduction relative to pure-water feeds. These results demonstrate how a controlled thin film model platform can isolate composition electrolyte relationships and provide mechanistic design principles for stable pure water anion exchange membrane electrolyzers.

Milenia Rojas Mendoza, B. [Stanford Univ., CA (Uni↗
DOE OSTI2019

Effects of anion size on flow electrification of polycarbonate and polyethylene terephthalate

Flow electrification at polymer surfaces has long been studied; yet, its mechanism is still not fully understood. In the current research, we experimentally investigated the surface electric potentials of polycarbonate and polyethylene terephthalate exposed to electrolyte solutions of various anion sizes. The surface potential was always negative, and its magnitude decreased as the anion became larger. Other important factors include the ion concentration and the flow rate. These results help precisely control the polymer charging process, important for electret processing, energy harvesting, biosensing, among others.

Kou, Rui↗
DOE OSTI2019

Vibrationally resolved photoelectron spectroscopy of oligothiophene radical anions

Vibrationally resolved photoelectron spectroscopy of terthiophene, quaterthiophene, and quinquethiophene radical anions is presented. The increased spectral resolution afforded by the combination of slow photoelectron velocity-map imaging and ion cooling in a cryogenic ion trap allows the characterization of vibronic structures within the S0 and T1 states. Analysis of the spectra, aided by electronic structure calculations and Franck-Condon simulations, revealed evidence for significant contributions from kinetically trapped higher energy conformers in the anion-to-triplet transitions. Unlike the lowest energy structures, where all the thiophene linkers are in the trans configuration, these higher energy conformers contain at least one cis linker. We also found that the adiabatic Franck-Condon simulations drastically underestimated the intensities of some vibronic features in the singlet ground state spectra due to large geometry changes upon photodetachment and anharmonic couplings in the singlet state.

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

Photoelectron spectra of early 3 d -transition metal dioxide molecular anions from GW calculations

Photoelectron spectra of early 3 d -transition metal dioxide anions, Sc O 2 - , Ti O 2 - , V O 2 - , Cr O 2 - , and Mn O 2 - , are calculated using semilocal and hybrid density functional theory (DFT) and many-body perturbation theory within the GW approximation using one-shot perturbative and eigenvalue self-consistent formalisms. Different levels of theory are compared with each other and with available photoelectron spectra. We show that one-shot GW with a PBE0 starting point ( G 0 W 0 @PBE0) consistently provides very good agreement for all experimentally measured binding energies (within 0.1 eV–0.2 eV or less). We attribute this to the success of PBE0 in mitigating self-interaction error and providing good quasiparticle wave functions, which renders a first-order perturbative GW correction effective. One-shot GW calculations with a Perdew–Burke–Ernzerhof (PBE) starting point do poorly in predicting electron removal energies by underbinding orbitals with typical errors near 1.5 eV. A higher exact exchange amount of 50% in the DFT starting point of one-shot GW does not provide very good agreement with experiment by overbinding orbitals with typical errors near 0.5 eV. While not as accurate as G 0 W 0 @PBE0, the G -only eigenvalue self-consistent GW scheme with W fixed to the PBE level provides a reasonably predictive level of theory (typical errors near 0.3 eV) to describe photoelectron spectra of these 3 d -transition metal dioxide anions. Adding eigenvalue self-consistency also in W , on the other hand, worsens the agreement with experiment overall. Overall, our findings on the performance of various GW methods are discussed in the context of our previous studies on other transition metal oxide molecular systems.

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

Vertical detachment energies of ammonia cluster anions using self-interaction-corrected methods

Systems with weakly bound extra electrons impose great challenges to semilocal density functional approximations (DFAs), which suffer from self-interaction errors. Small ammonia clusters are one such example of weakly bound anions where the extra electron is weakly bound. We applied two self-interaction correction (SIC) schemes, viz., the well-known Perdew–Zunger and the recently developed locally scaled SIC (LSIC) with the local spin density approximation (LSDA), Perdew–Burke–Ernzerhof (PBE) generalized gradient approximation (GGA), and the SCAN meta-GGA functionals to calculate the vertical detachment energies (VDEs) of small ammonia cluster anions (NH3)n–. Our results show that the LSIC significantly reduces the errors in calculations of VDE with LSDA and PBE-GGA functionals leading to better agreement with the reference values calculated with coupled cluster singles and doubles with perturbative triples [CCSD(T)]. Accurate prediction of VDE as an absolute of the highest occupied molecular orbital (HOMO) is challenging for DFAs. Our results show that VDEs estimated from the negative of HOMO eigenvalues with the LSIC-LSDA and Perdew–Zunger SIC-PBE are within 11 meV of the reference CCSD(T) results. Here, the LSIC method performs consistently well for the VDE estimates, from both the total energy differences and the absolute HOMO eigenvalues.

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

Use of FLOSIC for understanding anion-solvent interactions

An Achille’s heel of lower-rung density-functional approximations is that the highest-occupied-molecular-orbital energy levels of anions, known to be stable or metastable in nature, are often found to be positive in the worst case or above the lowest-unoccupied-molecular-orbital levels on neighboring complexes that are not expected to accept charge. A trianionic example, [Cr(C2O4)3]3−, is of interest for constraining models linking Cr isotope ratios in rock samples to oxygen levels in Earth’s atmosphere over geological timescales. Here we describe how crowd sourcing can be used to carry out self-consistent Fermi–Löwdin–Orbital-Self-Interaction corrected calculations (FLOSIC) on this trianion in solution. The calculations give a physically correct description of the electronic structure of the trianion and water. In contrast, uncorrected local density approximation (LDA) calculations result in approximately half of the anion charge being transferred to the water bath due to the effects of self-interaction error. Use of group-theory and the intrinsic sparsity of the theory enables calculations roughly 125 times faster than our initial implementation in the large N limit reached here. By integrating charge density densities and Coulomb potentials over regions of space and analyzing core-level shifts of the Cr and O atoms as a function of position and functional, we unambiguously show that FLOSIC, relative to LDA, reverses incorrect solute-solvent charge transfer in the trianion-water complex. In comparison to other functionals investigated herein, including Hartree–Fock and the local density approximation, the FLOSIC Cr 1s eigenvalues provide the best agreement with experimental core ionization energies.

Chemistry↗
DOE OSTI2024

Dynamics of hydride anion and acetyloxyl radical production by electron attachment to acetic acid

Here, we investigate the dynamics and site-selectivity in the dissociation of transient anions formed upon attachment of low energy electrons to acetic acid by anion fragment momentum imaging experiments. The resonances at 6.7 and 7.7 eV are confirmed to dissociate exclusively by the O–H bond, while a third resonance at 9.1 eV dissociates primarily by both C–H break and O–H break. A fourth resonance near 10 eV is found to dissociate by O–H break. For each resonance, the measured kinetic energy release indicates two-body dissociation produces a neutral radical in the ground electronic state, for all four resonances. The measured angular distributions are consistent with all four resonances having A' symmetry.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗