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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Redox Chemistry Mediated Control of Morphology and Properties in Electrically Conductive Coordination Polymers: Opportunities and Challenges

Coordination polymers (CPs) and metal–organic frameworks (MOFs) have attracted significant research interest in the past several decades due to their reticular structures and modularity. However, realizing electrically conductive CPs or MOFs with comparable properties to classic conducting organic polymers has only been a recent development. This emerging class of materials has found wide appli-cation in many fields due to combined features of structural rigidity, chemical tunability, porosity, and charge transport. Alongside many studies revealing myriad design approaches to access these materials, the role that redox chemistry plays in both material synthesis and modulation of electronic properties has been an emerging theme. This perspective provides a brief overview of select examples where redox chemistry medi-ates control of morphology and properties in electrically conductive CPs/MOFs. Here, the challenges and limitations in this area are also discussed. Particular challenges include the characterization of redox states in these materials and measuring and understanding highly correlated elec-tronic properties and other unusual physical phenomena which may be important for potential applications.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Redox effects on the structure and properties of Na-Mo-Fe-phosphate glasses

Na-Mo-Fe-phosphate glasses were prepared with reducing and oxidizing raw materials and the effects of the different Fe 2+ /Fe 3+ and Mo 5+ /Mo 6+ ratios on glass structure and properties were determined. Mssbauer spectroscopy confirms significantly greater concentrations of Fe 2+ ions in the reduced glasses and distorted Fe 3+ O 4 sites preferred over the Fe 3+ O 6 sites in the oxidized glasses. Raman spectroscopy reveals the presence of isolated Mo 6+ O 6 sites in the oxidized glasses, and highly distorted Mo 5+ O 5 sites in reduced Mo-rich glasses. The presence of specific Fe- and Mo-polyhedra is correlated with the average phosphate anion length, as characterized by high-pressure liquid chromatography. Generally, for the similar compositions, oxidized glasses have greater molar volumes than the reduced glasses, associated with the formation of isolated Mo 6+ O 6 octahedra and the absence of highly crosslinked Mo 5+ OPO 4 units. Tg increases with increasing Fe 3+ fractions in the Fe-rich glasses, whereas for the Mo-rich glasses, T g increases with greater Mo 5+ fractions.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Development of a TSR-based method for understanding structural relationships of cofactors and local environments in photosystem I

All chemical forms of energy and oxygen on Earth are generated via photosynthesis where light energy is converted into redox energy by two photosystems (PS I and PS II). There is an increasing number of PS I 3D structures deposited in the Protein Data Bank (PDB). The Triangular Spatial Relationship (TSR)-based algorithm converts 3D structures into integers (TSR keys). A comprehensive study was conducted, by taking advantage of the PS I 3D structures and the TSR-based algorithm, to answer three questions: (i) Are electron cofactors including P700, A -1 and A 0 , which are chemically identical chlorophylls, structurally different? (ii) There are two electron transfer chains (A and B branches) in PS I. Are the cofactors on both branches structurally different? (iii) Are the amino acids in cofactor binding sites structurally different from those not in cofactor binding sites? The key contributions and important findings include: (i) a novel TSR-based method for representing 3D structures of pigments as well as for quantifying pigment structures was developed; (ii) the results revealed that the redox cofactor, P700, are structurally conserved and different from other redox factors. Similar situations were also observed for both A -1 and A 0 ; (iii) the results demonstrated structural differences between A and B branches for the redox cofactors P700, A -1 , A 0 and A 1 as well as their cofactor binding sites; (iv) the tryptophan residues close to A 0 and A 1 are structurally conserved; (v) The TSR-based method outperforms the Root Mean Square Deviation (RMSD) and the Ultrafast Shape Recognition (USR) methods. The structural analyses of redox cofactors and their binding sites provide a foundation for understanding the unique chemical and physical properties of each redox cofactor in PS I, which are essential for modulating the rate and direction of energy and electron transfers.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Photoelectrochemical Imaging of Charge Separation between MoS 2 Triangles and Insulating SiO 2 Support

The role of the insulating support in photocatalysis is poorly understood. Using high-resolution photo-scanning electrochemical microscopy (photo-SECM), we observed significant spatial charge separation in few-layer-thick molybdenum disulfide (MoS 2 ) triangles attached to a SiO 2 substrate. Spatially resolved surface photovoltage (SPV) measurements revealed that photogenerated holes migrate from MoS 2 to the SiO 2 surface and travel laterally over distances exceeding 2 μm, driven by the builtin electric field of ~1.7 kV/cm. In thicker and less uniform flakes, the charge separation is dominated by internal driving forces within MoS 2 , without significant contribution from SiO 2 . These findings underscore the importance of insulator–semiconductor interactions for effective charge separation, suggesting a new strategy for optimizing photocatalytic systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1980

Advances in membrane technology for the NASA redox energy storage system

Anion exchange membranes used in the system serve as a charge transferring medium as well as a reactant separator and are the key enabling component in this storage technology. Each membrane formulation undergoes a series of screening tests for area-resistivity, static (non-flow) diffusion rate determination, and performance in Redox systems. The CDIL series of membranes has, by virtue of its chemical stability and high ion exchange capacity, demonstrated superior properties in the redox environment. Additional resistivity results at several acid and iron solution concentrations, iron diffusion rates, and time dependent iron fouling of the various membrane formulations are presented in comparison to past standard formulations.

Ling, J. S.↗
DOE OSTI2023

Effect of a redox-mediating ligand shell on photocatalysis by CdS quantum dots

Semiconductor quantum dots (QDs) are efficient organic photoredox catalysts due to their high extinction coefficients and easily tunable band edge potentials. Despite the majority of the surface being covered by ligands, our understanding of the effect of the ligand shell on organic photocatalysis is limited to steric effects. We hypothesize that we can increase the activity of QD photocatalysts by designing a ligand shell with targeted electronic properties, namely, redox-mediating ligands. Herein, we functionalize our QDs with hole-mediating ferrocene (Fc) derivative ligands and perform a reaction where the slow step is hole transfer from QD to substrate. Surprisingly, we find that a hole-shuttling Fc inhibits catalysis, but confers much greater stability to the catalyst by preventing a build-up of destructive holes. We also find that dynamically bound Fc ligands can promote catalysis by surface exchange and creation of a more permeable ligand shell. Finally, we find that trapping the electron on a ligand dramatically increases the rate of reaction. Furthermore, these results have major implications for understanding the rate-limiting processes for charge transfer from QDs and the role of the ligand shell in modulating it.

Chemistry↗
DOE OSTI2024

Model output from simulations of manganese-carbon interactions in temperate forest soil profiles

This archive contains model output, code, and scripts for simulations of coupled manganese-carbon cycling in temperate forest soil profiles. These model results were generated as part of a study investigating how manganese availability influences soil organic carbon stocks and demonstrating a new model framework for coupling carbon and manganese cycling. The simulations were in support of a manuscript: "Modeling interactive effects of manganese bioavailability, nitrogen deposition, and warming on soil carbon storage." The study addresses the research questions: How does Mn bioavailability, as driven by subsurface mineral properties, pH, and redox status, affect temperate forest soil organic carbon and litter carbon stocks?How is the relationship between Mn bioavailability and carbon cycling affected by changes in temperature and nitrogen deposition?"Model simulations were conducted in a reactive transport modeling framework using PFLOTRAN coupled to python. Multiple model simulations testing different Mn-bearing mineral solubilities, hydrological patterns, nitrogen deposition rates, and temperatures are included. Soil properties, including total and exchangeable Mn concentrations, are based on values reported for the Susquehanna Shale Hills Critical Zone Observatory (SSHCZO), a temperate forested watershed in central Pennsylvania, U.S.A where Mn cycling through vegetation has been documented.File formats include netCDF (.nc), python script (.py), shell script (.sh), plain text PFLOTRAN input file (.in), and plain text PFLOTRAN database file (.dat), and gzipped tar archive (tar.gz).

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1999

The Mars Environmental Compatibility Assessment (MECA)

The Mars Environmental Compatibility Assessment (MECA) will evaluate the Martian environment for soil and dust-related hazards to human exploration as part of the Mars Surveyor Program 2001 Lander. Sponsored by the Human Exploration and Development of Space (HEDS) enterprise, MECA's goal is to evaluate potential geochemical and environmental hazards that may confront future martian explorers, and to guide HEDS scientists in the development of high fidelity Mars soil simulants. In addition to objectives related to human exploration, the MECA data set will be rich in information relevant to basic geology, paleoclimate, and exobiology issues. The integrated MECA payload contains a wet-chemistry laboratory, a microscopy station, an electrometer to characterize the electrostatics of the soil and its environment, and arrays of material patches to study the abrasive and adhesive properties of soil grains. MECA is allocated a mass of 10 kg and a peak power usage of 15 W within an enclosure of 35 x 25 x 15 cm (figures I and 2). The Wet Chemistry Laboratory (WCL) consists of four identical cells that will accept samples from surface and subsurface regions accessible to the Lander's robotic arm, mix them with water, and perform extensive analysis of the solution. Using an array of ion-specific electrodes (ISEs), cyclic voltammetry, and electrochemical techniques, the chemistry cells will wet soil samples for measurement of basic soil properties of pH, redox potential, and conductivity. Total dissolved material, as well as targeted ions will be detected to the ppm level, including important exobiological ions such as Na, K+, Ca++, Mg++, NH4+, Cl, S04-, HC03, as well as more toxic ions such as Cu++, Pb++, Cd++, Hg++, and C104-. MECA's microscopy station combines optical and atomic-force microscopy (AFM) to image dust and soil particles from millimeters to nanometers in size. Illumination by red, green, and blue LEDs is augmented by an ultraviolet LED intended to excite fluorescence in the sample. Substrates were chosen to allow experimental study of size distribution, adhesion, abrasion, hardness, color, shape, aggregation, magnetic and other properties. To aid in the detection of potentially dangerous quartz dust, an abrasion tool measures sample hardness relative to quartz and a hard glass (Zerodur).

Meloy, Thomas P.↗
DOE OSTI2025

Adsorption and Chromatographic Behavior of Dispersed Sodium Bismuthate Systems for the Separation of Americium from Curium

The selective partitioning of americium (Am) and curium (Cm) is integral for nuclear science areas such as the nuclear fuel cycle, stockpile stewardship, and isotope production but remains a long-standing radioanalytical challenge due to nearly identical chemical properties. Differences in redox chemistry can be exploited since Am can be oxidized to the hexavalent oxidation state. Sodium bismuthate (NaBiO 3 ) exhibits favorable oxidation and ion exchange characteristics conducive to a rapid and efficient Am/Cm chromatographic separation. Contact of nitric acid with NaBiO 3 was shown to significantly decrease the nitric acid concentration and solution volume. The adsorption, kinetic, and chromatographic behavior of Am and Cm in systems that disperse NaBiO3 in filter aids was evaluated. Further, dispersion of NaBiO 3 increased separation factors to over 100, with rapid kinetics achieved within 1 min of contact and sustained for at least 2 h. The adsorption capacity was more than doubled from 0.066 mequiv g –1 for solid NaBiO 3 alone to 0.149(6) and 0.156(9) meq g –1 when dispersed in Celite 545 and silica gel, respectively. Complete separation was achieved in all systems with ~100% recovery in the respective eluted fractions.

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

Electron Radiation-Induced Nickel Nanoparticle Formation in KCl-ZnCl 2 Eutectic Molten Salt Using X-ray Absorption Spectroscopy

Understanding the speciation and local structure of metal solutes in molten salts is essential for predicting thermal properties and the redox and corrosion potentials of molten salts for next-generation nuclear reactors and concentrated solar power plant applications. Here, we employ X-ray absorption spectroscopy combined with electron paramagnetic resonance (EPR) measurements to investigate the effects of electron irradiation on 0.1 wt % NiCl 2 dissolved in molten eutectic KCl-ZnCl 2 salt. Radiation-driven reduction of Ni 2+ leading to nucleation and growth of Ni nanoparticles is studied as a function of electron dose (3–15 MGy) and temperature. Quantitative X-ray absorption near edge structure and linear combination fitting are utilized to investigate the extent of reduction as a function of the electron dose and temperature. A multiple-scattering (MS) approach is used for extended X-ray absorption fine structure analysis to deduce the size of the Ni nanoparticles formed and to understand the effect of the dose on the local structure of the nanoparticles. EPR studies on solidified NiCl 2 dissolved in molten eutectic KCl-ZnCl 2 salt show the formation of magnetic Ni nanoparticles.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Enhanced Catalytic Activity of a Vanadium-Doped Mesoporous Octahedral Molecular Sieve-2 (K-OMS-2) toward Hydrogen Evolution Reaction

Hydrogen evolution reaction (HER) is the cathodic reaction in electrochemical water splitting that produces H 2 in a renewable pathway, primarily to be used in fuel cells. K-OMS-2, a manganese octahedral molecular sieve, has the potential to replace Pt as a catalyst for HER due to its redox and electrochemical properties, which can be further improved by doping metal cations into the K-OMS-2 framework. In this work, we synthesized 1, 5, and 10% vanadium- (V) doped mesoporous K-OMS-2 under mild acidic reaction conditions. Here, the mesoporous nature of the samples was confirmed by BET analysis. X-ray photoelectron spectroscopy confirmed that Mn has 2+, 3 +, and 4+ oxidation states, and V is present as V 4+ in V-K-OMS-2 samples. HER performance of 1% V-K-OMS-2 in an acidic medium shows the best activity with -0.32 V overpotential. The overpotential was lowered by 0.56 V upon doping 1% V into the K-OMS-2 framework. The 1% V-K-OMS-2 material has a Tafel slope of 129 mV/decay and an electrochemically active surface area (ECSA) of 127.5 cm 2 ECSA .

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

Selective Electrochemical Capture and Release of Uranyl in Solution (Final Report)

The goal of this project is to investigate the selective, electrochemical capture and release of uranyl ((UO 2 ) 2 +) from biphasic or heterogeneous mixtures using a class of cluster molecules, ortho-carboranes (Cb), containing selective binding groups. Possible applications in PUREX, seawater uranyl extraction, or in actinide/lanthanide (An/Ln) or Ln/Ln separations are envisioned. With this funding, we sought to achieve these goals by harnessing the redox-switchable chelating properties of the “closo” Cb to the reduced “nido” Cb enabling the electrochemical control of the ligand bite angle. Using this premise, specific goals include: 1) integrating new selective coordinating groups (L) onto the carbon positions of Cb for the selective capture and release of uranyl, and; 2) anchoring these selective carboranes onto electrode and/or heterogeneous surfaces for the selective, heterogeneous capture and release of uranyl from aqueous solutions under flow conditions. Overall, this work focuses on advancing our understanding and controlling the properties of this new platform for metal capture and release chemistry which, we believe, has the potential for broader applicability in the separation sciences.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS1989

Viking Biology Experiments and the Martian soil

The Viking Biology Experiments (VBE) are the most informative database on the wet chemistry and reactivity of the Martian soil available today. The simulation and chemical interpretation of the results have given valuable hints towards the characterization of the soils' mineralogy, adsorption properties, pH and redox. The characterization of Mars' soil on the basis of ten years of labelled release (LR) and other VBE simulations are reviewed.

Banin, Amos↗
NASA NTRS2000

Sugars as the optimal biosynthetic carbon substrate of aqueous life throughout the universe

Our previous analysis of the energetics of metabolism showed that both the biosynthesis of amino acids and lipids from sugars, and the fermentation of organic substrates, were energetically driven by electron transfer reactions resulting in carbon redox disproportionation (Weber, 1997). Redox disproportionation--the spontaneous (energetically favorable) direction of carbon group transformation in biosynthesis--is brought about and driven by the energetically downhill transfer of electron pairs from more oxidized carbon groups (with lower half-cell reduction potentials) to more reduced carbon groups (with higher half-cell reduction potentials). In this report, we compare the redox and kinetic properties of carbon groups in order to evaluate the relative biosynthetic capability of organic substrates, and to identify the optimal biosubstrate. This analysis revealed that sugars (monocarbonyl alditols) are the optimal biosynthetic substrate because they contain the maximum number of biosynthetically useful high energy electrons/carbon atom while still containing a single carbonyl group needed to kinetically facilitate their conversion to useful biosynthetic intermediates. This conclusion applies to aqueous life throughout the Universe because it is based on invariant aqueous carbon chemistry--primarily, the universal reduction potentials of carbon groups.

NASA Center ARC↗
NASA NTRS1999

Sugars as the Optimal Biosynthetic Carbon Substrate of Aqueous Life throughout the Universe

Our previous analysis of the energetics of metabolism showed that both the biosynthesis of amino acids and lipids from sugars, and the fermentation of organic substrates, were energetically driven by electron transfer reactions resulting in carbon redox disproportionation (Weber 1997). Redox disproportionation -- the spontaneous (energetically favorable) direction of carbon group transformation in biosynthesis -- is brought about and driven by the energetically downhill transfer of electron pairs from more oxidized carbon groups (with lower half-cell reduction potentials) to more reduced carbon groups (with higher half-cell reduction potentials). In this report, we compare the redox and kinetic properties of carbon groups in order to evaluate the relative biosynthetic capability of organic substrates, and to identify the optimal biosubstrate. This analysis revealed that sugars (monocarbonyl alditols) are the optimal biosynthetic substrate because they contain the maximum number of biosynthetically useful .high energy electrons/carbon atom , while still containing a single carbonyl group needed to kinetically facilitate their conversion to useful biosynthetic intermediates. This conclusion applies to aqueous life throughout the Universe because it is based on invariant aqueous carbon chemistry -- primarily, the universal reduction potentials of carbon groups.

Weber, Arthur L.↗
DOE OSTI2024

Laser-engraved defects in TiO 2 support: Enhancing reducibility and redox capability of Pt/TiO 2 catalyst for reactive and selective hydrogenation

Titanium dioxide (TiO 2 ) has been studied as catalyst or catalyst support in catalysis. Its synthesis or modification approach controls the structural, optical, and electronic properties. Here, in this work, we applied laser engraving to the anatase TiO 2 and studied the consequent changes in its structure and property as well as the properties of TiO 2 supported platinum (i.e., Pt/TiO 2 ) catalyst. The laser engraving enlarged the particle size, formed rutile phase and created defects (i.e., oxygen vacancy (O v ) and Ti 3+ ) in anatase TiO 2 . This induced band gap change and enhanced visible light absorption. The defects created by laser engraving are stable and more reducible than those existed in the pristine TiO 2 . The defective TiO 2 is structurally stable and has great redox properties. The metal-support interaction in the Pt/defective TiO 2 catalyst is stronger than that of the pristine Pt/TiO 2 catalyst, which enabled higher reactivity and selectivity in hydrogenation of 3-nitrostyrene and furfuryl alcohol. Laser-engraved TiO 2 has been rarely studied for thermal catalysis. This work provides basic understanding of material properties and catalysis application of laser-engraved catalyst supports and catalysts in field of thermal catalysis.

25 ENERGY STORAGE↗