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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS2021

A Machine Learning Approach to Predict Aircraft Landing Times using Mediated Predictions from Existing Systems

We developed a novel approach for predicting the landing time of airborne flights in real-time operations. The first step predicts a landing time by using mediation rules to select from among physics-based predictions (relying on the expected flight trajectory) already available in real time in the Federal Aviation Administration System Wide Information Management system data feeds. The second step uses a machine learning model built upon the mediated predictions. The model is trained to predict the error in the mediated prediction, using features describing the current state of an airborne flight. These features are calculated in real time from a relatively small number of data elements that are readily available for airborne flights. Initial results based on five months of data at six large airports demonstrate that incorporating a machine learning model on top of the mediated physics-based prediction can lead to substantial additional improvements in prediction quality.

Machine learning↗
DOE OSTI2021

Electrochemical Activation of C–C Bonds via Mediated Hydrogen Atom Transfer Reactions

Activating inert sp 3 -sp 3 carbon-carbon (C-C) bonds remains a major bottleneck in the chemical upcycling of recalcitrant polyolefin waste. Here, we use redox mediators to activate the inert C-C bonds. Specifically, we use N -hydroxyphthalimide (NHPI) as the redox mediator that is oxidized to phthalimide- N -oxyl (PINO) radical to initiate hydrogen atom transfer (HAT) reactions with benzylic C-H bonds. The resulting carbon radical is readily captured by molecular oxygen to form a peroxide that decomposes into oxygenated C-C bond-scission fragments. This indirect approach reduces the oxidation potential by > 1.2 V compared to the direct oxidation of the substrate. Studies with model compounds revealed the selectivity of C-C bond cleavage increases with decreasing C-C bond dissociation energy. With NHPI-mediated oxidation, oligomeric styrene ( M n = 510 Da, OS 510 ) and polystyrene (PS, ~10,000 Da) were converted into oxygenated monomers, dimers, and oligomers.

09 BIOMASS FUELS↗
DOE OSTI2025

Water‐mediated Decomposition Pathways of ε‐Hexanitrohexaazaisowurtzitane

The dominant initial decomposition mechanism of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (HNIW) is understood from the literature to be the N─NO 2 bond scission unimolecular mechanism. Here we have found a water-mediated HONO release initial decomposition mechanism energetically competitive with the N─NO 2 bond scission mechanism modeled using ab initio nudged elastic band simulations. The activation energy of the water-mediated HONO mechanism was calculated to be 138.9 kJ/mol with the Perdew, Burke, and Ernzerhof (PBE) functional (177.8 with PBE0), while the double NO 2 release mechanism is 171.9 kJ/mol (203.3 with PBE0). Branching secondary, tertiary, and quaternary decomposition steps were also discovered including oxidation of HONO or H 2 O causing ring-opening that leads to C─N bond breaking and N 2 O or NO release. The reaction rate of HONO oxidation is much faster than HONO release, making the HONO concentration low. The Helmholtz free energy barrier of the double NO 2 release mechanism is lower than the water-mediated HONO release above 438 K (165°C) due to the vibrational contribution to the free energy. This helps explain why the literature reports more NO 2 release at higher temperatures. The present study reveals a physical mechanism for how water can catalyze the decomposition of HNIW at low enough temperatures, and reveals secondary, tertiary, and quaternary reaction mechanisms leading to NO x release. In conclusion, as water is realistically always present, the reported barriers are important for building kinetic models needed to ensure the safety and reliability of HNIW.

Steele, Brad A. [Lawrence Livermore National Labor↗
DOE OSTI2020

Search for light mediators in the low-energy data of the CONNIE reactor neutrino experiment

The CONNIE experiment is located at a distance of 30 m from the core of a commercial nuclear reactor, and has collected a 3.7 kg-day exposure using a CCD detector array sensitive to an~1 keV threshold for the study of coherent neutrino-nucleus elastic scattering. Here we demonstrate the potential of this low-energy neutrino experiment as a probe for physics Beyond the Standard Model, by using the recently published results to constrain two simplified extensions of the Standard Model with light mediators. We compare the new limits with those obtained for the same models using neutrinos from the Spallation Neutron Source. Our new constraints represent the best limits for these simplified models among the experiments searching for CE$ν$NS for a light vector mediator with mass $ {M}_{Z^{\prime }} $< 10 MeV, and for a light scalar mediator with mass M$_{\phi}$< 30 MeV. These results constitute the first use of the CONNIE data as a probe for physics Beyond the Standard Model.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Search for heavy resonances decaying to ZZ or ZW and axion-like particles mediating nonresonant ZZ or ZH production at $\sqrt{s}$ = 13 TeV

A search has been performed for heavy resonances decaying to ZZ or ZW and for axion-like particles (ALPs) mediating nonresonant ZZ or ZH production, in final states with two charged leptons (ℓ = e, μ) produced by the decay of a Z boson, and two quarks produced by the decay of a Z, W, or Higgs boson H. The analysis is sensitive to resonances with masses in the range 450 to 2000 GeV. Two categories are defined corresponding to the merged or resolved reconstruction of the hadronically decaying boson. The search is based on data collected during 2016–2018 by the CMS experiment at the LHC in proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb -1 . No significant excess is observed in the data above the standard model background expectation. Upper limits on the production cross section of heavy, narrow spin-2 and spin-1 resonances are derived as functions of the resonance mass, and exclusion limits on the production of bulk graviton particles and W' bosons are calculated in the framework of the warped extra dimensions and heavy vector triplet models, respectively. In addition, upper limits on the ALP-mediated diboson production cross section and ALP couplings to standard model particles are obtained in the framework of linear and chiral effective field theories. These are the first limits on nonresonant ALP-mediated ZZ and ZH production obtained by the LHC experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2026

Kinetic control of phase evolution and defect-mediated recombination in AACVD-grown copper antimony sulphide thin films

Copper antimony sulphide (CAS) is a multinary chalcogenide semiconductor in which small deviations from stoichiometry can drive phase competition and strong defect-mediated modulation of optoelectronic properties. However, the systematic roles of copper precursor fraction and deposition time in governing phase evolution, off-stoichiometry, and recombination dynamics in aerosol-assisted chemical vapour deposition (AACVD)-grown undoped CAS thin films remain insufficiently understood. In this work, undoped CAS thin films were deposited by AACVD using Cu(dedtc)2 and Sb(dedtc)3 single-source precursors at 550 °C and a carrier gas flow rate of 150 sccm, while the Cu(dedtc)2 mole fraction (x = 0.15 – 0.55) and deposition time (1 – 2 hours) were systematically varied to probe how growth kinetics influence phase composition, microstructure, and defect-mediated optical properties without post-deposition annealing or extrinsic doping. Increasing copper precursor content drives phase evolution toward tetrahedrite-dominant CAS films at intermediate Cu(dedtc)2 mole fractions, with the film deposited at x = 0.35 exhibiting the strongest tetrahedrite character within the parameter space examined. The films are also copper-rich, antimony-poor, and sulphur-deficient, consistent with off-stoichiometric growth and intrinsic defect formation, plausibly including copper interstitials, Cu-on-Sb antisites, and sulphur vacancies. These growth-dependent compositional deviations are accompanied by tunable indirect optical bandgaps of approximately 1.60 – 2.18 eV and weak visible photoluminescence governed by defect-mediated recombination. Time-resolved photoluminescence reveals bi-exponential decay behaviour with lifetimes of approximately 0.1 – 3.6 ns, with emission dominated by slower donor–acceptor pair recombination and a smaller contribution from faster trap-assisted pathways. Collectively, these results establish an explicit kinetic process–structure–defect–property relationship for AACVD-grown CAS thin films and provide a growth–structure–property framework relevant to future optimization of CAS-based optoelectronic and energy materials.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Reduction of uranyl and uranyl-organic complexes mediated by magnetite and ilmenite: A combined electrochemical AFM and DFT study

Reduction of mobile aqueous uranyl complexes can be hindered by the strength of the uranyl-ligand complex and the resistivity of the complexes to electron transfer. Semiconducting solids, such as magnetite (Fe 3 O 4 ) and ilmenite (FeTiO 3 ), can facilitate otherwise-slow electron transfer between the reductant and oxidant, especially if these species are adsorbed on their surfaces as inner-sphere complexes. Electrons can then be shuttled through the surface or the structure. This process can be facilitated by either finding a new electron transfer path or by weakening or destroying the ligand-uranyl complex. Using in situ electrochemical atomic force microscopy (EC-AFM), we imaged reduction products of uranyl as mediated by magnetite and ilmenite in the absence or presence of the organic ligands, ethylenediaminetetraacetate (EDTA) and oxalate. In situ images of uranyl reduction show gradual nucleation and growth of reduced uranium on the mineral surfaces with decreasing reduction potentials. X-ray photoelectron spectroscopy (XPS) measurements indicate pentavalent uranium as the dominant uranium species resulting from uranyl reduction mediated by magnetite and ilmenite. The reduction potentials of uranyl-organic species relevant to our reaction system, (U VI O 2 ∙oxalate) 0 and (U VI O 2 ∙HEDTA) - , are derived using quantum–mechanical modeling and compared with the midpoint potentials obtained from cyclic voltammetry measurements. The spectroscopic, electrochemical, and computational data suggest that the catalysis of Fe-bearing minerals facilitates the reduction of uranyl-organic complexes. U(VI)-oxalate complexes are redox-active and participate directly in the reduction mediated by magnetite. In the presence of EDTA, reduction of uranyl may proceed in concert with ligand exchange between metals (i.e., U and Fe) on the mineral surface. Finally, the proposed mechanism is the breaking of uranyl-organic bonds upon interaction with the mineral surface followed by the formation of Fe-organic bonds, thereby allowing the reduction of hexavalent uranyl to pentavalent one.

58 GEOSCIENCES↗
DOE OSTI2023

Mn(III)-mediated bisphenol a degradation: Mechanisms and products

Bisphenol A (BPA) is a high production volume chemical with potential estrogenic effects susceptible to abiotic degradation by MnO 2 . BPA transformation products and reaction mechanisms with MnO 2 have been investigated, but detailed process understanding of Mn(III)-mediated degradation has not been attained. Rapid consumption of BPA occurred in batch reaction vessels with 1 mM Mn(III) and 63.9 ± 0.7% of 1.76 ± 0.02 μmol BPA was degraded in 1 hour at circumneutral pH. BPA was consumed at 1.86 ± 0.09-fold higher rates in vessels with synthetic MnO 2 comprising approximately 13 mol% surface-associated Mn(III) versus surface-Mn(III)-free MnO 2 , and 10–35% of BPA transformation could be attributed to Mn(III) during the initial 10-min reaction phase. High-resolution tandem mass spectrometry (HRMS/MS) analysis detected eight transformation intermediates in reactions with Mn(III), and quantum calculations proposed 14 BPA degradation products, nine of which had not been observed during MnO 2 -mediated BPA degradation, suggesting mechanistic differences between Mn(III)- versus MnO 2 -mediated BPA degradation. Finally, the findings demonstrate that both Mn(III) and Mn(IV) can effectively degrade BPA and indicate that surface-associated Mn(III) increases the reactivity of synthetic MnO 2 , offering opportunities for engineering more reactive oxidized Mn species for BPA removal.

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

Molten-salt-mediated carbon dioxide capture and superequilibrium utilization with ethane oxidative dehydrogenation

Existing CO 2 -mediated oxidative dehydrogenation (CO 2 -ODH) of ethane has yet to demonstrate >60% single-pass CO yield due to the intrinsic equilibrium limitations. We report a unique approach with mixed molten carbonates as a reaction medium for CO 2 -ODH, which strategically partitions the CO 2 -ODH reactions into gas and molten-salt phases and facilitates integrated CO 2 capture from power plant flue gases. An 89% CO yield was achieved at 770°C, doubling the equilibrium limitation of conventional CO 2 -ODH. The high CO yield in turn enhances ethylene formation. Further characterizations confirmed that molten-salt mediated ODH (MM-ODH) proceeds through a gas-phase cracking and molten-salt mediated reverse water-gas-shift reaction pathway. Based on this understanding, thermodynamic analysis and ab initio molecular dynamics simulations were conducted to develop general principles to optimize the molten-salt reaction medium. Process analyses confirm that MM-ODH has the potential to be significantly more efficient for CO 2 capture and utilization than conventional CO 2 -ODH.

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

TRIM27-mediated ubiquitination of PPARγ promotes glutamate-induced cell apoptosis and inflammation

Neurotoxicity induced by glutamate (Glu) is often used to study the signaling mechanism of neurological disorders. The identification of specific genetic factors that cause Glu-induced neurotoxicity provides evidence for the common pathways of neuronal apoptosis and inflammation. TRIM27 has been found to induce apoptosis and inflammation. Nevertheless, there is little evidence that TRIM27 is associated with Glu-induced neurotoxicity. We found that TRIM27 expression was increased in epilepsy patients and in HT22 cells following Glu treatment. Glu-mediated cell apoptosis, decreased PPARγ expression, and increased levels of cleaved Caspase-3 and IL-1β expression in HT22 cells were significantly inhibited by TRIM27 knockdown. TRIM27 overexpression significantly induced cell apoptosis and expression of cleaved Caspase-3 and IL-1β, but inhibited PPARγ expression in HT22 cells, which were reversed by ROZ, suggesting the involvement of PPARγ in TRIM27-mediated cell apoptosis and inflammation in HT22 cells. Mechanically, TRIM27 ubiquitinates and degrades PPARγ, following induces cleaved Caspase-3 and IL-1β expression. Clinically, increased expression of TRIM27 in epilepsy patients was associated with decreased PPARγ expression. Taken together, our study suggests that TRIM27-mediated ubiquitination of PPARγ promotes Glu-induced HT22 cell apoptosis and IL-1β release.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

BAP1 antagonizes WWP1-mediated transcription factor KLF5 ubiquitination and inhibits autophagy to promote melanoma progression

Accumulating evidence revealed the abnormal expression of KLF5 in human cancers while its role in melanoma remains uncharacterized. This study aimed to explore the role of KLF5 in the proliferation and metastasis of melanoma. Bioinformatics analysis was performed to detect WWP1, BAP1 and KLF5 expression in melanoma, followed by expression determination on clinical tissues from melanoma patients and cancer cells. The cancer cells were infected with lentivirus expressing KLF5 or BAP1 while PI3K, AKT and mTOR expression was detected and autophagy was observed. Treated cells were injected to mice when tumor growth was measured and autophagy-related protein was detected. Plasmids expressing WWP1 and Ub-K48 were co-transfected into treated melanoma cells while immunoprecipitation assay was performed to determine the interaction among KLF5, WWP1, and BAP1. WWP1 was poorly expressed in melanoma cells and tissues whereas KLF5 was highly expressed and was positively correlated to poor prognosis. KLF5 promoted melanoma cell malignant phenotypes as well as inhibited autophagy. Interestingly, KLF5 contributed to activation of PI3K-AKT-mTOR signaling pathway, thereby inhibiting autophagy in melanoma cells. WWP1 mediated K48-linked ubiquitination of KLF5 to promote its degradation, and BAP1 antagonized this modification and stabilized KLF5 protein expression. Besides, BAP1 promoted KLF5-mediated growth of melanoma in vivo. Taken altogether, BAP1 antagonized WWP1-mediated ubiquitination of KLF5 to inhibit autophagy and promote melanoma development.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

Up-regulating TIPE2 alleviates inflammatory pain by suppressing microglial activation-mediated inflammatory response via inhibiting Rac1/NF-κB pathway

TNF-α-inducible protein 8-like 2 (TIPE2) is a recently discovered regulator of inflammation that can maintain immune homeostasis, exerting a significant role in the development of inflammation-related diseases. Here, we aimed to explore the role and potential regulatory mechanism of TIPE2 in the progression of inflammatory pain. In the present study, a mouse BV2 microglia cell activation-mediated inflammatory model was developed with LPS induction, and a mouse inflammatory pain model was established with complete Freund's adjuvant (CFA) injection. In vitro, the TIPE2 expression was decreased in LPS-induced BV2 cells. Overexpression of TIPE2 mitigated LPS-medicated microglial activation via decreasing nitric oxide (NO) generation and the expression of microglia marker IBA-1. Notably, increasing TIPE2 expression alleviated microglial activation-triggered expression levels and releases of proinflammatory factors such as TNF-α, IL-1β, and IL-6. Mechanism analysis verified that overexpression of TIPE2 blunted Rac1-mediated activation of NF-κB pathway following LPS stimulation. More importantly, CFA injection reduced the expression of TIPE2 in a mouse inflammatory pain model and overexpression of TIPE2 alleviated CFA-mediated pain hypersensitivity and inflammatory response, and inactivated microglia cell in vivo. Furthermore, overexpression of TIPE2 decreased Rac1 expression and suppressed the activation of NF-κB pathway in spinal cord after CFA injection. In summary, the present study revealed that overexpression of TIPE2 mitigated inflammatory pain through suppressing microglial activation-induced inflammation by inactivating Rac1/NF-κB pathway. The study provides a novel theoretical foundation for the therapy of inflammatory pain.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2026

First-Principles Insights into Proton-Coupled Electron Transfer versus Hydrogen Evolution Reaction Selectivity from a Base-Appended Cobaltocene Mediator

Performing selective proton-coupled electron transfer (PCET) to substrates such as N 2 , CO 2 , and unsaturated organic molecules under electrochemical conditions requires the suppression of the competing hydrogen evolution reaction (HER). To address this challenge, our laboratory previously demonstrated a PCET mediator strategy using a dimethylaniline-appended cobaltocene complex, [(CpCoCp NMe2 )H] + , which performs selective reductive chemistry while suppressing the HER. However, the origin of the suppressed, yet still observable, HER has not been thoroughly established. In this work, we perform density functional theory (DFT) calculations to elucidate the HER mechanism involving this redox mediator and to provide atomistic insights into the bifurcation between the PCET and HER pathways. We find that protonation of the aniline moiety to form [CpCoCp NMe2H ] + is more favorable, both kinetically and thermodynamically, than formation of the ring-protonated species [(CpCo(Cp-H) NMe2 )] + . Furthermore, PCET to acetophenone is energetically more favorable via [CpCoCp NMe2H ] + than via [(CpCo(Cp-H) NMe2 )] +1/0 . In contrast, the most favorable HER pathway involves the ring-protonated Co(I) species. These results offer mechanistic insights into HER versus PCET bifurcation and establish guiding principles for designing PCET mediators for selective electroreductive transformations.

evolution reactions↗
DOE OSTI2020

Investigation of Complex Intermediates in Solvent-Mediated Synthesis of Thiophosphate Solid-State Electrolytes

Lithium thiophosphates represent a promising class of solid Li + conductors for all-solid-state batteries. Scalable solvent-mediated synthesis routes for several Li–P–S ternary compounds have been reported, but little is known regarding the reaction mechanism of such pathways. This work demonstrates that solvent-mediated synthesis of lithium thiophosphate solid electrolytes from mixtures of Li 2 S and P 2 S 5 proceeds through a highly soluble P 2 S 6 2– intermediate. This intermediate exhibits virtually the same Raman spectra in several solvents including acetonitrile, methyl acetate, ethyl acetate, ethyl propionate, dimethoxyethane, tetraethylene glycol dimethyl ether, and tetrahydrofuran. Additionally, based on this universal intermediate, a general reaction mechanism is proposed for the solvent-mediated synthesis of several lithium thiophosphates including (LiPS 3 ) n , Li 2 P 2 S 6 , Li 7 P 3 S 11 , and Li 3 PS 4 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Substrate-Mediated Evaporation and Stochastic Evolution of Supported Au Nanoparticles

Here, we use in situ transmission electron microscopy with automated tracking to study supported gold nanoparticles (NPs) during high-temperature vacuum annealing. The average mass loss per NP is governed by a flat, nearly size-independent substrate-mediated evaporation profile. On top of this mean shrinkage, individual NPs show significant fluctuations in apparent growth or shrinkage, and NP volume follows a random-walk-like trajectory. To rationalize both the ensemble-mean behavior and the particle-resolved variability, we develop a self-consistent theory that couples substrate-mediated evaporation to collective 2D Ostwald-type mass exchange through a shared adatom field, described in terms of a renormalized screening length and background concentration. In the experimentally relevant regime, the theory predicts an approximately size-independent mean shrinkage rate and clarifies how net mass loss suppresses classical coarsening. Superimposed on this deterministic drift, we quantify stochastic volume trajectories and capture their fluctuation spectrum with a minimal Langevin description consistent with intermittent adatom attachment and detachment events. In addition, we characterize the lateral diffusive motion of NPs, which is responsible for their coalescence. Altogether, our results highlight that stochasticity is intrinsic at the nanoscale and that predicting the evolution of supported NPs at early and intermediate times requires a unified framework combining substrate-mediated evaporation, collective mass exchange, and stochastic fluctuations.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2020

Determinants for Efficient Editing with Cas9-Mediated Recombineering in Escherichia coli

In E. coli, editing efficiency with Cas9-mediated recombineering varies across targets due to differences in the level of Cas9:gRNA-mediated DNA double-strand break (DSB)-induced cell death. We found that editing efficiency with the same gRNA and repair template can also change with target position, cas9 promoter strength, and growth conditions. Incomplete editing, off-target activity, nontargeted mutations, and failure to cleave target DNA even if Cas9 is bound also compromise editing efficiency. These effects on editing efficiency were gRNA-specific. We propose that differences in the efficiency of Cas9:gRNA-mediated DNA DSBs, as well as possible differences in binding of Cas9:gRNA complexes to their target sites, account for the observed variations in editing efficiency between gRNAs. We show that editing behavior using the same gRNA can be modified by mutating the gRNA spacer, which changes the DNA DSB activity. Finally, we discuss how variable editing with different gRNAs could limit high-throughput applications and provide strategies to overcome these limitations.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Catalytic, Spectroscopic, and Theoretical Studies of Fe 4 S 4 -Based Coordination Polymers as Heterogenous Coupled Proton–Electron Transfer Mediators for Electrocatalysis

Iron–sulfur clusters play essential roles in biological systems, and thus synthetic [Fe 4 S 4 ] clusters have been an area of active research. Recent studies have demonstrated that soluble [Fe 4 S 4 ] clusters can serve as net H atom transfer mediators, improving the activity and selectivity of a homogeneous Mn CO 2 reduction catalyst. Here, in this work, we demonstrate that incorporating these [Fe 4 S 4 ] clusters into a coordination polymer enables heterogeneous H atom transfer from an electrode surface to a Mn complex dissolved in solution. A previously reported solution-processable Fe 4 S 4 -based coordination polymer was successfully deposited on the surfaces of different electrodes. The coated electrodes serve as H atom transfer mediators to a soluble Mn CO 2 reduction catalyst displaying good product selectivity for formic acid. Furthermore, these electrodes are recyclable with a minimal decrease in activity after multiple catalytic cycles. The heterogenization of the mediator also enables the characterization of solution-phase and electrode surface species separately. Surface enhanced infrared absorption spectroscopy (SEIRAS) reveals spectroscopic signatures for an in situ generated active Mn–H species, providing a more complete mechanistic picture for this system. The active species, reaction mechanism, and the protonation sites on the [Fe 4 S 4 ] clusters were further confirmed by density functional theory calculations. The observed H atom transfer reactivity of these coordination polymer-coated electrodes motivates additional applications of this composite material in reductive H atom transfer electrocatalysis.

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

Calcium-mediated nitrogen reduction for electrochemical ammonia synthesis

Ammonia (NH 3 ) is a key commodity chemical for the agricultural, textile and pharmaceutical industries, but its production via the Haber–Bosch process is carbon-intensive and centralized. Alternatively, an electrochemical method could enable decentralized, ambient NH 3 production that can be paired with renewable energy. The first verified electrochemical method for NH 3 synthesis was a process mediated by lithium (Li) in organic electrolytes. So far, however, elements other than Li remain unexplored in this process for potential benefits in efficiency, reaction rates, device design, abundance and stability. In our demonstration of a Li-free system, we found that calcium can mediate the reduction of nitrogen for NH 3 synthesis. Here we verified the calcium-mediated process using a rigorous protocol and achieved an NH 3 Faradaic efficiency of 40 ± 2% using calcium tetrakis(hexafluoroisopropyloxy)borate (Ca[B(hfip) 4 ] 2 ) as the electrolyte. Our results offer the possibility of using abundant materials for the electrochemical production of NH 3 , a critical chemical precursor and promising energy vector

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗