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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 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Fabrication of a composite anion exchange membrane with aligned ion channels for a high-performance non-aqueous vanadium redox flow battery

Fabrication of high-conductivity ion exchange membranes (IEMs) is crucial to improve the performance of non-aqueous vanadium redox flow batteries (NAVRFBs). In the present work, anion exchange membranes with high-conductivity were fabricated by aligning ion channels of the polymer electrolyte impregnated in porous polytetrafluoroethylene (PTFE) under electric fields. It was observed that the ion channels of the polymer electrolyte were uniformly orientated in the atomic-force microscopy image. Its morphological change could minimize detouring of the transport of BF 4 - ions. The results showed through-plane conductivity was improved from 12.7 to 33.1 mS cm -1 . The dimensional properties of the fabricated membranes were also enhanced compared with its cast membrane owing to the reinforcing effect of the substrate. Especially, the NAVRFB assembled with the optimized membrane showed increased capacities, with a 97% coulombic efficiency and 70% energy efficiency at 80 mA cm -2 . Furthermore, the optimized membrane made it possible to operate the NAVRFB at 120 mA cm -2 . Its operating current density was 120 times higher than that of a frequently used AHA membrane for RFBs.

25 ENERGY STORAGE↗
DOE OSTI2020

Expanding the potential of redox carriers for flow battery applications

Here, using theoretical modeling to guide our approach, substituents were selected to improve the negative and positive potentials associated with a representative metal-based redox carrier, a phenyl spaced nickel bispicolinamide complex, [Ni(bpb)], 1. To broaden the cell potential, electron donating groups were selected and installed on the pyridyl moieties, [Ni(bpb-(NMe 2 ) 2 )], 2, while electron withdrawing groups were incorporated on the phenyl linker, [Ni(bpb-R)] (R = –F, –CF 3 , and –NO 2 ), 3–5. Our model predicts an increase of ~300 mV and ~500 mV for the first and second negative waves of Ni(bpb-NMe 2 ), 2, and up to ~330 mV and ~210 mV increase to the first and second positive waves in 3–5. The modeled complexes were synthesized in good yields using a modification of the literature procedure. Due to limited solubility, the differential pulse voltammetry was measured on complexes 2–5 using a drop cast technique. Comparison of the observed and predicted potentials is discussed in acetonitrile (MeCN) and dimethylformamide (DMF) solvents.

25 ENERGY STORAGE↗
DOE OSTI2023

High temperature gamma radiation-induced chromium redox chemistry via in situ spectroscopic measurements

Chromium ions can make their way into the primary coolant of nuclear power reactors from the corrosion of stainless-steel reactor components, decreasing the material's corrosion resistance and resulting in increased transport of further corrosion products. Despite these potential effects, the radiation-induced redox speciation of chromium ions in aqueous solution is not well understood, especially at the elevated temperatures experienced by reactor coolants. Here, in the present work, we report new experimental results demonstrating that in aerated aqueous solution, the radiolytic oxidation of Cr(III) to Cr(VI) occurs at pH 4, while the reduction of Cr(VI) to Cr(III) occurs at pH 2. The oxidation of Cr(III) is primarily attributed to the reaction of the hydroxyl radical (˙OH) with the Cr(OH) 2+ species, while the reduction of Cr(VI) is attributed to reactions involving the hydrated electron (e aq - ) and hydrogen atom (H˙). Additionally, the steady-state equilibrium yield of Cr(VI) from the gamma irradiation of pH 4 Cr(III) solutions decreased with increasing temperature (over a range of 37–195 °C). This observation indicates that the activation energy of the Cr(VI) reduction reactions is higher than that for the Cr(III) oxidation reactions, such that it becomes relatively more favorable at higher temperatures. Overall, these data are important for the development of complementary multiscale models for the prediction of metal ion speciation in high temperature radiation environments.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2020

Redox Potential Measurements of Cr(II)/Cr Ni(II)/Ni and Mg(II)/Mg in Molten MgCl 2 –KCl–NaCl Mixture

The redox potential of Ni(II)/Ni, Cr(II)/Cr, and Mg(II)/Mg in MgCl 2 –KCl–NaCl (Magnak chloride) were studied utilizing chronopotentiometry (CP) method in a three-electrode electrochemical cell. Four different CrCl 2 concentrations from 873 K to 1073 K, three NiCl 2 concentrations from 773 K to 1073 K, and two MgCl 2 concentrations from 823 K to 1073 K have been measured. The activity coefficients were calculated referring to a supercooled potential accordingly. The empirical equation of formal potential will be of great significance for the fundamental thermodynamic prediction in high-temperature Magnak chloride systems where corrosion product impurities are present.

14 SOLAR ENERGY↗
DOE OSTI2021

Methods—Design Guidelines for Tubular Flow-through Electrodes for Use in Electroanalytical Studies of Redox Reaction Kinetics

The tubular flow-through electrode (FTE) is a facile electroanalytical tool for investigating electrochemical reaction kinetics; however, its suitability for this purpose requires careful design and operation under conditions that guarantee uniform current distribution. In this perspective article, we provide a scaling analysis of the transport and reaction processes within a tubular FTE leading to quantitative guidelines for the FTE design and operation. Two dimensionless parameters (classical Wagner number Wa I and modified Wagner number incorporating the effect of mass transport Wa II ) are utilized to compare the magnitudes of the ohmic, activation and transport resistances of the tubular FTE, and to quantify its current distribution uniformity. With the aid of analytical modeling of the current distribution, optimal ranges for these two dimensionless parameters are defined so as to ascertain uniform current distribution. Application of these guidelines to a graphite tubular FTE is shown to enable the precise determination of the charge-transfer kinetics of the ferri/ferrocyanide redox reaction.

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

Ambient Temperature Sodium Polysulfide Catholyte for Nonaqueous Redox Flow Batteries

This study reports a sodium polysulfide catholyte for nonaqueous redox flow batteries (RFBs). We demonstrate reversible capacities up to 200 mAh/gS with negligible fade over 250 cycles at room temperature for sodium polysulfide|biphenyl full cells containing Na + ß '' -Al 2 O 3 solid electrolyte (BASE) membranes. Interestingly, formation of insoluble S and Na 2 S 4 phases did not inhibit the catholyte's cycle life which is likely due to the low concentrations used in the lab-scale prototypes. 3-electrode galvanostatic AC impedance measurements demonstrate that voltage losses were dominated by charge transfer at the cathode, and relevant kinetic parameters (i.e., transfer coefficients and exchange current density) were calculated through a Tafel analysis. To the best of our knowledge, this is the first report applying such an impedance approach to nonaqueous RFBs. Overall, the use of low-cost active materials makes sodium polysulfide|biphenyl RFBs promising for long duration energy storage applications. Furthermore, if strategies are developed to increase the solubility of S and/or low order polysulfides (Na 2 S x , x ≤ 4), specific energies up to 100 Wh kg -1 (including combined mass of the anolyte and catholyte) can be achieved.

25 ENERGY STORAGE↗
DOE OSTI2023

Electrochemical Deposition with Redox Replacement of Lanthanum with Uranium in Molten LiCl-KCl

Electrochemical recovery of dilute concentrations of actinides from spent nuclear fuel would reduce the longevity of storing high-level nuclear waste. Electrochemical deposition with redox replacement (EDRR) is used in a molten salt medium for the selective electrochemical recovery of uranium in the presence of excess concentrations of lanthanum. In each EDRR cycle, after a short electrodeposition pulse, the deposited lanthanum is spontaneously replaced by uranium at open circuit. After repeated cycles, uranium metal was obtained on a tungsten electrode immersed in LiCl-KCl melt that contained 1 wt.% lanthanum chloride – 0.15 wt.% uranium 4+ chloride. Here, scanning electron microscopy and energy dispersive X-ray spectroscopy analysis revealed uranium particles approximately 0.5 - 1 μm with well-defined rectangular shapes; and with 20 – 60 times more uranium recovered on the surface of the electrode than lanthanum.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2023

Electrode Blocking Due to Redox Reactions in Aluminum Chloride-Sodium Iodide Molten Salts

Iodide redox reactions in molten NaI/AlCl 3 are shown to generate surface-blocking films, which may limit the useful cycling rates and energy densities of molten sodium batteries below 150 °C. An experimental investigation of electrode interfacial stability at 110 °C reveals the source of the reaction rate limitations. Electrochemical experiments in a 3-electrode configuration confirm an increase of resistance on the electrode surface after oxidation or reduction current is passed. Using chronopotentiometry, chronoamperometry, cyclic voltammetry, and electrochemical impedance spectroscopy, the film formation is shown to depend on the electrode material (W, Mo, Ta, or glassy carbon), as well as the Lewis acidity and molar ratio of I − /I 3 − in the molten salt electrolytes. These factors impact the amount of charge that can be passed at a given current density prior to developing excessive overpotential due to film formation that blocks the electrode surface. The results presented here guide the design and use of iodide-based molten salt electrolytes and electrode materials for grid scale battery applications.

25 ENERGY STORAGE↗
DOE OSTI2026

Quantifying Energy Storage Density Utilization Trends in Redox Flow Battery Chemistries

The transition to new energy resources is driving the need for efficient energy storage. Redox flow batteries (RFBs) are a promising solution due to their flexible design and safer materials, particularly for long-duration storage applications. Despite these advantages, RFB technologies still have considerable room for growth in terms of utilizing all of their available energy storage density. Herein, we assess RFB energy storage density utilization trends for multiple chemistries by accounting for their unique thermodynamic limits, energy efficiencies, and charge capacity constraints. Of the RFBs chemistries analyzed, most still use less than 60% of their theoretical energy storage capacity. The conventional all-vanadium RFB was the closest to its thermodynamic limit available. Moreover, the volumetric footprint and electrolyte cost analyses demonstrate the real-world implications of these inefficiencies. This analysis further indicates that future studies would benefit from clearer reporting of two key quantities: discharge efficiency, which is more directly tied to practically recoverable energy density than round-trip energy efficiency, and state-of-charge or capacity-utilization limits, which govern access to theoretical storage capacity. More consistent reporting of these factors would improve the accuracy and comparability of energy storage utilization analyses across RFB chemistries.

battery energy storage↗
DOE OSTI2026

Mechano-chemical understanding of NaSICON for aqueous redox-flow batteries

Redox-flow batteries utilizing a sodium superionic conductor (NaSICON) can be cost-effective systems for grid energy storage by combining high sodium selectivity with reliance on abundant, low-cost elements. However, improving membrane toughness while maintaining a sufficiently thin membrane for ion conduction is needed. Addressing this issue requires deeper insight into the mechanical properties of NaSICON, its interactions with aqueous chemistries, and the chemo-mechanical degradation mechanisms that arise at the intersection of these phenomena. Here, we provide a framework for understanding these problems, strategies to address them, and highlight the potential of unconventional sintering and thin-film fabrication to optimize the performance of NaSICON in practical flow cells.

Grid energy storage↗
DOE OSTI2024

Manufacturing of Fabric Electrodes using a High-Throughput Screening Platform for Redox Flow Batteries

The objective of this project is to establish a new manufacturing methodology with machine learning- based high-throughput screening for the design and development of hierarchical structured, high-performance fabric electrodes for redox flow batteries (RFBs). The end goal of the project is to design and manufacture fabric electrodes for RFB applications that can provide 250 mA/cm2 current density operation for 100-cycles with 80% average energy efficiency. This was accomplished by first examining the structure-performance-property linkages of the electrodes provided by our partner, AvCarb. The electrodes’ microstructure was characterized by determining their pore size distribution, tortuosity, specific surface area, and porosity. The ohmic, charge transfer and mass transfer resistances were then calculated using electrochemical impedance spectroscopy. Carbon cloth electrodes showed the greatest resistance, which was dominated by charge transfer resistance, which we believe is related to the surface functionalization. Full cell cycling was used in order to determine the area specific resistance and energy efficiency of the cells. All of this experimental data and the results of the mathematical model (to increase the amount of inputs with parametric sweeping) were used to develop a machine learning-based model for the design of high-performance fabric electrodes. Using the results from the machine learning tool, optimized electrodes were fabricated by AvCarb. The ohmic, charge transfer and mass transfer resistances for these new electrodes were measured, and both performed better than any of the initial samples which had been provided by AvCarb.

25 ENERGY STORAGE↗
DOE OSTI2020

Redox and Thiols in Archaea

Low molecular weight (LMW) thiols have many functions in bacteria and eukarya, ranging from redox homeostasis to acting as cofactors in numerous reactions, including detoxification of xenobiotic compounds. The LMW thiol, glutathione (GSH), is found in eukaryotes and many species of bacteria. Analogues of GSH include the structurally different LMW thiols: bacillithiol, mycothiol, ergothioneine, and coenzyme A. Many advances have been made in understanding the diverse and multiple functions of GSH and GSH analogues in bacteria but much less is known about distribution and functions of GSH and its analogues in archaea, which constitute the third domain of life, occupying many niches, including those in extreme environments. Archaea are able to use many energy sources and have many unique metabolic reactions and as a result are major contributors to geochemical cycles. As LMW thiols are major players in cells, this review explores the distribution of thiols and their biochemistry in archaea.

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

An Overview of the Design and Optimized Operation of Vanadium Redox Flow Batteries for Durations in the Range of 4–24 Hours

An extensive review of modeling approaches used to simulate vanadium redox flow battery (VRFB) performance is conducted in this study. Material development is reviewed, and opportunities for additional development identified. Various crossover mechanisms for the vanadium species are reviewed, and their effects on its state of charge and its state of health assessed. A stack design focusing on flow fields and an electrode design tailored to various flow fields are reviewed. An operational strategy that takes these parameters into account is reviewed for various operating envelopes, chosen based on end user preference in terms of minimizing capital cost or operation and maintenance cost. This work provides a framework for the design and operation of a VRFB for various grid services.

25 ENERGY STORAGE↗
NASA NTRS2018

Redox Signaling and Its Impact on Skeletal and Vascular Responses to Spaceflight

Spaceflight entails exposure to numerous environmental challenges with the potential to contribute to both musculoskeletal and vascular dysfunction. The purpose of this review is to describe current understanding of microgravity and radiation impacts on the mammalian skeleton and associated vasculature at the level of the whole organism. Recent experiments from spaceflight and groundbased models have provided fresh insights into how these environmental stresses influence mechanisms that are related to redox signaling, oxidative stress, and tissue dysfunction. Emerging mechanistic knowledge on cellular defenses to radiation and other environmental stressors, including microgravity, are useful for both screening and developing interventions against spaceflight-induced deficits in bone and vascular function.

redox siggnalin↗
NASA NTRSDate not supplied

Enhancing the Sensitivity of Redox Detection in Search-for-Life Missions Using Chemical Vapor Deposition (CVD) Graphene Electrodes

The primary objective for this effort is to fabricate and characterize redox-active molecules using CVD graphene as working electrodes using standard "on-chip" lithographic techniques. We then plan to move away from “on-chip” graphene electrodes and study methods for CVD graphene transfer that can also accommodate in-space manufacturing (ISM), enabling the use of this technology for crewed mission operations of the future.

graphene↗
DOE OSTI2023

Atomic Layer Deposition for Spatial Control of Redox Reaction Selectivity

Photocatalytic water splitting holds great potential in the pursuit of the U.S. Department of Energy's Hydrogen Shot initiative to bring the cost of H2 to $1/kg by 2031. A key challenge in the development of photocatalysts is increasing their overall solar-to-hydrogen efficiency by enhancing charge separation yields and redox selectivity. In this work, we use area selective ALD of oxide films to develop tunable interphase layers for selective oxidation and reduction reactions on a single substrate. This presentation details initial synthesis and characterization of Pt- and Au-based planar thin film electrodes in which Au regions were deactivated towards ALD growth through self-assembled thiol monolayers. The suppression of TiO2 ALD selectivity of thiols was assessed through ellipsometry, X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry. A patterned planar sample comprised of interdigitated arrays of Au and Pt, used as a surrogate for a photocatalyst particle containing two different co-catalysts, was exposed to ALD growth and removal of the inhibitor species. Scanning electrochemical microscopy (SECM) was used then to probe the local activity of different regions of the patterned surface towards the hydrogen evolution reaction (HER) and iron oxidation and correlated with the ionic and e- blocking effects of the area selective ALD coating. We will also detail the application of these findings to the ongoing development of 3D, particle-based photocatalysts.

atomic layer deposition↗