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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Lithium Solvation and Mobility in Ionic Liquid Electrolytes with Asymmetric Sulfonyl-Cyano Anion

The solvation structure and transport properties of Li + in ionic liquid (IL) electrolytes based on n-methyl-n-butylpyrrolidinium cyano(trifluoromethanesulfonyl)imide [PYR 14 ][CTFSI] and [Li][CTFSI] (0 ≤ x Li ≤ 0.7) were studied by Raman and Nuclear Magnetic Resonance (NMR) diffusometry, and molecular dynamics (MD) simulations. At x Li < 0.3, Li + coordination is dominated by the cyano group. As x Li is increased, free cyano-sites become limited, resulting in increased coordination via the sulfonyl group. Here, the 1:1 mixture of the symmetric anions bis(trifluoromethanesulfonyl)imide ([TFSI]) and dicyanamide ([DCA]) results in similar physical properties as the IL with [CTFSI]. However, anion asymmetry is shown to increase Li-salt solubility and promote Li+ transference. The lifetimes of Li + -cyano coordination for [CTFSI] are calculated to be shorter than those for [DCA], indicating that the competition from the sulfonyl group weakens its solvation with Li + . This resulted in higher Li + transference for the electrolyte with [CTFSI]. In relation to the utility of these electrolytes in energy storage, the Li–LiFePO 4 half cells assembled with IL electrolyte (x Li = 0.3, 0.5, and 0.7) demonstrated a nominal capacity of 140 mAh/g at 0.1C rate and 90 °C where the cell with x Li = 0.7 IL electrolyte demonstrated 61% capacity retention after 100 cycles and superior rate capability owing to increased electrochemical stability.

25 ENERGY STORAGE↗
DOE OSTI2022

Water Network Shape-Dependence of Local Interactions with the Microhydrated –NO 2 – and –CO 2 – Anionic Head Groups by Cold Ion Vibrational Spectroscopy

We report the structural evolutions of water networks and solvatochromic response of the CH 3 NO 2 – radical anion in the OH and CH stretching regions by analysis of the vibrational spectra displayed by cryogenically cooled CH 3 NO 2 – ·(H 2 O) n=1–6 clusters. The OH stretching bands evolve with a surprisingly large discontinuity at n = 6, which features the emergence of an intense, strongly red-shifted band along with a weaker feature that appears in the region assigned to a free OH fundamental. Very similar behavior is displayed by the perdeuterated carboxylate clusters, RCO 2 – ·(H 2 O) n=5–7 (R = CD 3 CD 2 ), indicating that this behavior is a general feature in the microhydration of the triatomic anionic domain and not associated with CH oscillators. Electronic structure calculations trace this behavior to the formation of a “book” isomer of the water hexamer that adopts a configuration in which one of the water molecules resides in an acceptor–acceptor–donor (AAD) (A = acceptor, D = donor) H-bonding site. Excitation of the bound OH in the AAD site explores the local network topology best suited to stabilize an incipient –XO 2 H–OH–(H 2 O) 2 intracluster proton-transfer reaction. These systems thus provide particularly clear examples where the network shape controls the potential energy landscape that governs water network-mediated, intracluster proton transfer. The CH stretching bands of the CH 3 NO 2 – ·(H 2 O) n=1–6 clusters also exhibit strong solvatochromic shifts, but in this case, they smoothly blue-shift with increasing hydration with no discontinuity at n = 6. Furthermore, this behavior is analyzed in the context of the solute-ion polarizability response and partial charge transfer to the water networks.

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

Atomistic Insights into Lithium–Glyme Solvate Ionic Liquids: Effects of Chain Length and Anion Coordination

For this study, mixtures of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in diglyme (G2), triglyme (G3) and tetraglyme (G4) at solvate ionic liquid (SIL) concentrations were investigated using classical molecular dynamics (cMD) simulations with a physically motivated force-field specifically developed for modeling these systems. The structural and dynamical properties of the mixtures were computed and analyzed. Lithium solvation shells, radial distribution functions, and X-ray structure factors were studied across the different SIL systems. Translational diffusion and rotational relaxation times were also evaluated, exhibiting similar trends with increasing glyme chain length. The results are consistent with experimental data and in good agreement with previous computational studies on G3 and G4. These findings validate the accuracy of the force field in modeling glyme systems and its use for describing the [Li(G2) 4/3 ][TFSI] mixture. Additionally, the thermal and electrochemical stability of these electrolytes were systematically examined. The thermal stability appears to be governed by cooperative interactions among glyme molecules, while the electrochemical stability is primarily influenced by Li + -anion interactions, which vary significantly with glyme chain length. Overall, the study sheds light on the crucial role of the anion in these glyme-based SILs and offers valuable insights into Li + -glyme systems at SIL concentrations, highlighting their promise as potential Li-ion battery electrolytes.

anions↗
DOE OSTI2022

Anion Effects on the Interfacial Structure and Bulk Physical Properties in Choline-Based Hydrogen-Bonded Electrolytes

Electrolytes consisting of choline (Ch) salts with acetate (Ac) and oxalate (Ox) anions were studied in mixtures with ethylene glycol (EG), in comparison to chloride (Cl)- and bis(trifluorosulfonyl)imide (TFSI)-containing systems to understand the impact of anion size and charge density on the bulk electrolyte and interfacial properties. These represent hydrogen-bonded concentrated electrolytes where the Ch salts are the H-bond acceptors (HBAs) and EG is the H-bond donor (HBD) in 1:2 and 1:4 HBA:HBD ratios. Increased H-bonding in Ch 2 Ox with EG compacts the liquid compared to ChAc, consistent with the increased dissociation energies of the HBA:HBD clusters with Ox –2 calculated by density functional theory (DFT), thus leading to denser and more viscous liquids. Electrochemical impedance spectroscopy (EIS) and surface-enhanced Raman spectroscopy (SERS) were used to investigate interfacial charge density and the electrode surface species. Differential capacitance curves demonstrate weak dependence on potential except for ChAc:EG, where Ac – is found to adsorb on the Au surface, in particular at +0.055 V vs Ag quasi-reference while no specific adsorption was observed on glassy carbon (GC). In situ SERS measurement confirms the formation of a surface layer in the ChAc:EG systems resulting from a Au–acetate interaction. Despite the structural similarities, Ox –2 did not show specific binding or any dependence of capacitance on potential as a result of strongly solvating EG molecules via H-bonds. Furthermore, this study shows that the charge density of the HBAs impacts both bulk properties and the electrical double-layer formation in concentrated H-bonded electrolytes that is relevant to electrochemical kinetics and morphology in electrodeposition processes and energy storage applications.

25 ENERGY STORAGE↗
DOE OSTI2023

Effect of Anions on the Delithiation of [Li–Al] Layered Double Hydroxides: Thermodynamic Insights

The utilization of lithium aluminum [Li–Al] layered double hydroxides (LDHs) is explored for direct lithium extraction (DLE) from geothermal brines and minerals. Following extraction, the Li + ions need to be removed from the LDH structure and converted into LiOH or Li 2 CO 3 products, making them suitable for battery applications. The research investigates the delithiation of [Li–Al-X] LDHs (where X = Cl – , OH – , and SO 4 2– ), which were synthesized and dried under different conditions. Herein the study aims to understand how the choice of anions and drying conditions affects the delithiation process. To determine the stability of these [Li–Al] LDHs, high-temperature oxide melt solution calorimetry is employed. The results reveal that the stability of LDHs varies significantly based on postdrying conditions, anion choice, and the water content in the interlayer. The order of stability, as indicated by the enthalpy of formation values, is found to be OH-LDH-O > OH-LDH-A > SO 4 -LDH-O > SO4-LDH-A > Cl-LDH-O > Cl-LDH-A. This trend is attributed to the interactions among the interlayer species and the metal hydroxide layers.

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

Resonant Two-Photon Photoelectron Imaging and Intersystem Crossing from Excited Dipole-Bound States of Cold Anions

In this work, we report the observation of a dipole-bound state (DBS) 659 cm –1 below the electron detachment threshold of cryogenically cooled deprotonated 4,4'-biphenol anion (bPh – ) and 19 of its lowest vibrational levels. Resonant two-photon photoelectron imaging (R2P-PEI) via the vibrational levels of the DBS displays a sharp peak with a constant binding energy. This observation indicates vertical detachment from the vibrational levels of the DBS to the corresponding neutral levels with the conservation of the vibrational energy, suggesting that the highly diffuse electron in the DBS has little effect on the neutral core. The R2P-PEI spectra also exhibit two features at lower binding energies, which come from intersystem crossings from the DBS to two lower-lying valence-bound triplet excited states of bPh – . The current study discloses the first R2P-PEI spectra from vibrational excited states of a DBS and direct spectroscopic evidence of transitions from a DBS to valence-bound states of anions.irect spectroscopic evidence of transitions from a DBS to valence-bound states of anions.

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

Probing the Critical Dipole Moment To Support Excited Dipole-Bound States in Valence-Bound Anions

We report, in this paper, photodetachment spectroscopy and high-resolution photoelectron imaging of para -halogen substituted phenoxide anions, p -XC 6 H 4 O – (X = F, Cl, Br, I). The dipole moments of the p -XC 6 H 4 O neutral radicals increase from 2.56 to 3.19 D for X = F to I, providing a series of similar molecules to allow the examination of charge-dipole interactions by minimizing molecule-dependent effects. Excited DBSs ([XC 6 H 4 O]* – ) are observed for the four anions with binding energies of 8, 11, 24, and 53 cm –1 , respectively, for X = F to I, below their respective detachment thresholds. The binding energies exhibit a linear correlation with the dipole moments of the neutral radicals, extrapolating to a critical dipole moment of 2.5 D for zero binding energy. Because of the small binding energy of the excited DBS of [FC 6 H 4 O]* – , rotational autodetachment is observed to compete with vibrational autodetachment in the resonant photoelectron spectra, resulting in electrons with near zero kinetic energies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

2-Isopropenyl-2-oxazoline: Well-Defined Homopolymers and Block Copolymers via Living Anionic Polymerization

Poly(2-isopropenyl-2-oxazoline) (PIPOx) has drawn significant attention for numerous applications. However, the successful living anionic polymerization of 2-isopropenyl-2-oxazoline has not been reported previously. In this paper, we describe how well-defined PIPOx with quantitative yields, controlled molecular weights from 6800 to over 100 000 g/mol and low polydispersity indices (PDI ≤ 1.17) were synthesized successfully via living anionic polymerization using diphenylmethylpotassium/diethylzinc (DPM-K/Et 2 Zn) in tetrahydrofuran (THF) at 0 °C. In particular, we report the precise synthesis of well-defined PIPOx with the highest molecular weight ever reported (over 100 000 g/mol) and low PDI of 1.17. The resulting polymers were characterized by 1 H and 13 C nuclear magnetic resonance spectroscopy (NMR) along with size exclusion chromatography (SEC). Additionally, the reactivity of living PIPOx was investigated by crossover block copolymerization with styrene (St), 2-vinylpyridine (2VP), and methyl methacrylate (MMA). It was found that the nucleophilicity of living PIPOx is of this order: living PS > living P2VP > living PMMA > living PIPOx. The self-assembly behavior in bulk of PIPOx-b-PS-b-PIPOx triblock copolymers having different block ratios of 10:80:10 and 25:50:25 was studied using transmission electron microscopy (TEM). Finally, the formation of spherical and lamellar nanostructures, respectively, was observed.

2-isopropenyl-2-oxazoline↗
DOE OSTI2019

Novel Ordered Rocksalt-Type Lithium-Rich Li 2 Ru 1–x Ni x O 3-δ (0.3 ≤ x ≤ 0.5) Cathode Material with Tunable Anionic Redox Potential

In this work, a series of ordered rocksalt (OR) type Li-rich Li 2 Ru 1–x Ni x O 3-δ (LRN x O, 0.3 ≤ x ≤ 0.5) are successfully synthesized and investigated for the first time. X-ray diffraction and neutron powder diffraction patterns exhibit an obvious phase transition from layered to an OR structure as the Ni content gradually increases from x = 0 to x = 0.5, which leads to different electrochemical behaviors. In the case of OR-LRN 0.4 O, an ~350 mV decrease of the oxygen oxidation potential compared with Li 2 RuO 3 (LRO) is observed from around 4.2 to 3.85 V, which is confirmed by both X-ray photelectron O 1s spectra and dQ/dV results. Additionally, the role of Ni substitution on the oxygen redox reaction is studied by first-principles calculations, and it is concluded that the formation of the OR structure caused by Ni substitution is the main reason for lowering the oxygen oxidation potential. In addition, the average discharge voltage of OR-LRN 0.4 O is also enhanced compared with LRO. This work provides a novel innovative strategy to modulate and control the oxygen anion redox reaction for high-energy-density Li-rich materials, which shed light on the fundamental understanding and optimizing of the anion redox process in Li-rich materials.

25 ENERGY STORAGE↗
DOE OSTI2025

Unraveling Anion-Specific Inhibition and Structural Modulation of Gibbsite Crystallization: Implications for Aluminum Mobility in Natural and Engineered Systems

Gibbsite (α-Al(OH) 3 , sometimes designated as γ-Al(OH) 3 ) plays a crucial role in the chemistry of aluminum in the environment and industry, yet its crystallization behavior under multianionic conditions is not well understood. Here, in this study, we investigate how six common anions─fluoride (F – ), chloride (Cl – ), bromide (Br – ), nitrate (NO 3 – ), sulfate (SO 4 2– ), and phosphate (PO 4 3– )─influence the mineralization, structure, and morphology of gibbsite at room temperature. The results show that PO 4 3– , SO 4 2– , and F – strongly inhibit gibbsite formation, stabilizing amorphous or alternative crystalline phases such as nordstrandite and cryolite. On the contrary, Cl – , Br – , and NO 3 – allow partial to complete crystallization of gibbsite without significant morphological changes. Solid-state 27 Al magic angle spinning nuclear magnetic resonance provides crucial insight into aluminum coordination environments in both crystalline and amorphous phases, distinguishing between octahedral, pentahedral, and tetrahedral Al species. The density functional theory calculations reveal a direct correlation between the Al–X bond strength and the inhibition of crystallization, following the order: PO 4 3– > SO 4 2– > F – > NO 3 – > Cl – > Br – . These findings offer molecular-scale insights into anion-specific effects on aluminum hydroxide nucleation and transformation, improving the understanding of gibbsite formation and aluminum cycling in soils, phosphate retention, contaminant immobilization, and waste treatment strategies in nuclear and industrial settings. These insights can also guide the controlled synthesis of aluminum hydroxide materials with tailored crystallinity and morphology via liquid-assisted methods.

Anions effect↗
DOE OSTI2011

Comproportionation of Cationic and Anionic Tungsten Complexes Having an N -Heterocyclic Carbene Ligand To Give the Isolable 17-Electron Tungsten Radical CpW(CO) 2 (IMes) •

A series consisting of a tungsten anion, radical and cation, supported by the N-heterocyclic carbene IMes (1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene) and spanning formal oxidation states W(0), W(I) and W(II), has been synthesized, isolated, and characterized. Reaction of the hydride CpW(CO)2(IMes)H with KH and 18 crown 6 gives the tungsten anion [CpW(CO)2(IMes)]-[K(18 crown 6)]+. The crystal structure of this complex shows that the K+ interacts not only with the oxygen atoms in the crown ether, but also with the carbonyl oxygens. The electrochemical oxidation of [CpW(CO)2(IMes)]- in acetonitrile is fully reversible (E½ = -1.65 V vs Cp2Fe+•/0) at all scan rates, indicating that CpW(CO)2(IMes)• is a persistent radical. Hydride transfer from CpW(CO)2(IMes)H to Ph3C+PF6 affords [cis-CpW(CO)2(IMes)(MeCN)]+PF6 . Comproportionation of [CpW(CO)2(IMes)]- with [CpW(CO)2(IMes)(MeCN)]+ gives the 17-electron tungsten radical CpW(CO)2(IMes)•. This complex shows paramagnetically shifted resonances in 1H NMR spectra and has been characterized by IR spectroscopy, low-temperature EPR spectroscopy, and X-ray diffraction. CpW(CO)2(IMes)• is very stable with respect to disproportionation and dimerization. NMR studies of degenerate electron transfer between CpW(CO)2(IMes)• and [CpW(CO)2(IMes)]- are reported. DFT calculations were carried out on CpW(CO)2(IMes)H, as well as on related complexes bearing NHC ligands with N,N´ substituents Me [CpW(CO)2(IMe)H] or H [CpW(CO)2(IH)H] to compare to the experimentally studied IMes complexes with mesityl substituents. These calculations reveal W H homolytic bond dissociation energies (BDEs) to decrease with increasing steric bulk of the NHC ligand, from 67 for CpW(CO)2(IH)H to 64 for CpW(CO)2(IMe)H to 63 kcal/mol for CpW(CO)2(IMes)H. The calculated spin density at W for CpW(CO)2(IMes)• is 0.63. The W radicals CpW(CO)2(IMe)• and CpW(CO)2(IH)• are calculated to form weak W W bonds. The weakly bonded complexes [CpW(CO)2(IMe)]2 and [CpW(CO)2(IH)]2, are predicted to have W-W BDEs of 6 and 18 kcal/mol, respectively, and to dissociate readily to the W-centered radicals CpW(CO)2(IMe)• and CpW(CO)2(IH)•. This work was supported by the US Department of Energy Basic Energy Sciences' Chemical Sciences, Geosciences & Biosciences Division. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Revitalizing Iron Redox by Anion-Insertion-Assisted Ferro- and Ferri-Hydroxides Conversion at Low Alkalinity

Iron hydroxides are desirable alkaline battery electrodes for low cost and environmental beneficence. However, hydrogen evolution on charging and Fe 3 O 4 formation on discharging cause low storage capacity and poor cycling life. Here, we report that green rust (GR) (Fe 2+ 4 Fe 3+ 2 (HO – ) 12 SO 4 ), formed via sulfate insertion, promotes Fe(OH) 2 /FeOOH conversion and shows a discharge capacity of ~211 mAh g –1 in half-cells and Coulombic efficiency of 93% after 300 cycles in full-cells. Theoretical calculations show that Fe(OH) 2 /FeOOH conversion is facilitated by intercalated sulfate anions. Classical molecular dynamics simulations reveal that electrolyte alkalinity strongly impacts the energetics of sulfate solvation, and low alkalinity ensures fast transport of sulfate ions. Anion-insertion-assisted Fe(OH) 2 /FeOOH conversion, also achieved with Cl – ion, paves a pathway toward efficient utilization of Fe-based electrodes for sustainable applications.

25 ENERGY STORAGE↗
DOE OSTI2011

Unveiling N-Protonation and Anion-Binding Effects on Fe/N/C Catalysts for O2 Reduction in Proton-Exchange-Membrane Fuel Cells

The high cost of proton-exchange-membrane fuel cells would be considerably reduced if platinum-based catalysts were replaced by iron-based substitutes, which have recently demonstrated comparable activity for oxygen reduction but whose cause of activity decay in acidic medium has been elusive. Here, we reveal that the activity of Fe/N/C catalysts prepared through a pyrolysis in NH{sub 3} is mostly imparted by acid-resistant FeN{sub 4} sites whose turnover frequency for the O{sub 2} reduction can be regulated by fine chemical changes of the catalyst surface. We show that surface N-groups protonate at pH 1 and subsequently bind anions. This results in decreased activity for the O{sub 2} reduction. The anions can be removed chemically or thermally, which restores the activity of acid-resistant FeN{sub 4} sites. These results are interpreted as an increased turnover frequency of FeN{sub 4} sites when specific surface N-groups protonate. These unprecedented findings provide a new perspective for stabilizing the most active Fe/N/C catalysts known to date.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2011

Experimental and Digital Modeling Studies of the Electrochemical Oxidation of the Metal Anion [CpW(CO)2(IMes)]- and the 17-Electron Metal Radical CpW(CO)2(IMes)•. Kinetics and Thermodynamics of Capture and Release of MeCN by a Metal Radical and a Metal Cation

The electrochemistry of [CpW(CO)2(IMes)] [K(18 crown 6)]+ (Cp = η5-C5H5, IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene), CpW(CO)2(IMes)•, and [CpW(CO)2(IMes)(MeCN)]+PF6 were studied by cyclic voltammetry in MeCN (0.2 M nBu4N+BF4 ). The tungsten anion [CpW(CO)2(IMes)]- showed a fully reversible one-electron oxidation with E½ = 1.65 V vs. Cp2Fe+/0. Oxidation of the resultant 17-electron radical CpW(CO)2(IMes)• was irreversible at all scan rates, affording the 18-electron solvent adduct [CpW(CO)2(IMes)(MeCN)]+. Reduction of [CpW(CO)2(IMes)(MeCN)]+ proceeded with loss of coordinated MeCN, and was followed by a second reduction to generate [CpW(CO)2(IMes)]-. Simultaneous digital simulation of voltammograms of [CpW(CO)2(IMes)]- and CpW(CO)2(IMes)• over a range of scan rates and concentrations gave estimates for E° of 0.491(2) V for the [CpW(CO)2(IMes)]+/• couple and 1.92 V for the [CpW(CO)2(IMes)(MeCN)]+/• couple. The neutral 19-electron radical complex CpW(CO)2(IMes)(MeCN)• is a stronger reducing agent (by 1.42 V) than the unsolvated 17-electron radical CpW(CO)2(IMes)•. Binding of MeCN by the unsolvated 16-electron cation [CpW(CO)2(IMes)]+ is exergonic with Keq = 1.2 × 1011 M 1 for [CpW(CO)2(IMes)]+ + MeCN [CpW(CO)2(IMes)(MeCN)]+. Expulsion of the MeCN ligand from the 19-electron complex CpW(CO)2(IMes)(MeCN)• is also exergonic, with Keq = 1.2 × 1013 M for CpW(CO)2(IMes)(MeCN)• CpW(CO)2(IMes)• + MeCN. Experimental and simulated cyclic voltammograms also account for the chemical reduction of the metal cation [CpW(CO)2(IMes)(MeCN)]+ by the metal anion [CpW(CO)2(IMes)]-, which ultimately produces two equivalents of the metal-centered radical CpW(CO)2(IMes)• This work was supported by the US Department of Energy Basic Energy Sciences' Chemical Sciences, Geosciences & Biosciences Division. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

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

Anionic redox reaction triggered by trivalent Al 3+ in P3-Na 0.65 Mn 0.5 Al 0.5 O 2

P3-Na 0.65 Mn 0.5 Al 0.5 O 2 (NMAO) has been synthesized and studied as a cathode for sodium batteries, and shows anionic redox reaction (ARR) and exhibits a first charging capacity of ~110 mA h g -1 . The electrochemical mechanism of NMAO was comprehensively investigated by X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and density functional theory (DFT) calculations. The reversible oxygen redox behaviour is triggered by Al 3+ through oxygen quasi non-bonding states generated by the relatively ionic interaction of Al and O. Furthermore, the presence of Al 3+ can suppress oxygen loss in ARR. Overall, this work provides new insights into the design and mechanism of anionic redox active cathode materials.

25 ENERGY STORAGE↗
DOE OSTI2026

Molecular insights into CO 2 -to-bicarbonate transformation in functionalized anion exchange ionomers for electrochemical separations

Bipolar membrane (BPM) electrochemical processes are a promising platform for carbon dioxide (CO 2 ) separations, but the molecular level thermodynamic and kinetic understanding of CO 2 -to-bicarbonate (HCO 3 − ) transformation remain poorly understood. This study employs a multiscale computational approach to systematically explore the adsorption and reactive transformation of CO 2 in five anion exchange ionomer systems. Classical molecular dynamics (MD) simulation results demonstrate that polymers with imidazolium groups significantly reduce CO 2 diffusion and enhance (OH − )–CO 2 interactions due to stronger electrostatic and π-interactions. Compared to the commonly used quaternary ammonium ionomers, imidazolium-functionalized ionomers show improved CO 2 proximity and interaction strength. Ab initio MD and density functional theory (DFT) calculations reveal that the benzyl-substituted imidazolium (IM-Ben) substantially reduces the energy barrier for HCO 3 − formation (∼72 meV lower) compared to the alkyl-substituted IM-nBu, while also mitigating imidazolium deprotonation under moderate hydration conditions. Transition state analysis shows IM-Ben forms more extensive hydrogen-bonding networks, which stabilize the transition state structure and contribute to a lower energy barrier for bicarbonate formation. These findings highlight the advantage of the adjacent benzyl moiety in enabling efficient CO 2 -to-bicarbonate transformation via hydrated hydroxide ion counterions, offering mechanistic insights and clear molecular design principles for optimizing anion exchange ionomers at bipolar membrane interfaces for electrochemical CO 2 separation applications.

Bipolar membranes, Reactive transformation of CO2,↗
DOE OSTI2014

Discovery of multiple, ionization-created CS{sub 2} anions and a new mode of operation for drift chambers

This paper focuses on the surprising discovery of multiple species of ionization-created CS{sub 2} anions in gas mixtures containing electronegative CS{sub 2} and O{sub 2}, identified by their slightly different drift velocities. Data are presented to understand the formation mechanism and identity of these new anions. Regardless of the micro-physics, however, this discovery offers a new, trigger-less mode of operation for the drift chambers. A demonstration of trigger-less operation is presented.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Comparison of the interactions in the rare gas hydride and Group 2 metal hydride anions

We study both the rare gas hydride anions, RG–H{sup −} (RG = He–Rn) and Group 2 (Group IIa) metal hydride anions, M{sub IIa}H{sup −} (M{sub IIa} = Be–Ra), calculating potential energy curves at the CCSD(T) level with augmented quadruple and quintuple basis sets, and extrapolating the results to the basis set limit. We report spectroscopic parameters obtained from these curves; additionally, we study the Be–He complex. While the RG–H{sup −} and Be–He species are weakly bound, we show that, as with the previously studied BeH{sup −} and MgH{sup −} species, the other M{sub IIa}H{sup −} species are strongly bound, despite the interactions nominally also being between two closed shell species: M(ns{sup 2}) and H{sup −}(1s{sup 2}). We gain insight into the interactions using contour plots of the electron density changes and population analyses. For both series, the calculated dissociation energy is significantly less than the ion/induced-dipole attraction term, confirming that electron repulsion is important in these species; this effect is more dramatic for the M{sub IIa}H{sup −} species than for RG–H{sup −}. Our analyses lead us to conclude that the stronger interaction in the case of the M{sub IIa}H{sup −} species arises from sp and spd hybridization, which allows electron density on the M{sub IIa} atom to move away from the incoming H{sup −}.

74 ATOMIC AND MOLECULAR PHYSICS↗