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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Potential-Dependent Adhesion Forces between dsDNA and Electroactive Surfaces

A promising approach to regulating the interactions between polyelectrolytes and materials is the use of electroactive surfaces that can change their charge state. However, common electroactive groups are too unstable to be practical for this purpose. Here we have performed a single molecule force spectroscopy study of the interactions between dsDNA and an 1,1'-biferrocenylene (BFD = bis(fulvalene)diiron)-terminated self-assembled monolayer surface that allows us to reversibly change the charge state. We found that the interaction force between DNA and the surface is correlated to the oxidation state of the BFD groups, which is conveniently controlled by the electrochemical potentials. We discovered that the electroactive SAM produces much stronger interaction forces than its nonelectroactive counterpart. A model based on the Grahame equation was able to quantitatively reproduce the experimentally observed relation between the applied potentials and adhesion forces. Our electroactive surface provides a model system for quantitative studies of the interactions between polyelectrolyte and charged surfaces in liquid. Furthermore, these insights may enable new opportunities for actively manipulating the binding, orientations, and conformations of polyelectrolytes for biosensing, nanomotors, and other applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Strong Lithium Polysulfide Chemisorption on Electroactive Sites of Nitrogen-Doped Carbon Composites For High-Performance Lithium–Sulfur Battery Cathodes

Despite the high theoretical capacity of lithium–sulfur batteries, their practical applications are severely hindered by a fast capacity decay, stemming from the dissolution and diffusion of lithium polysulfides in the electrolyte. A novel functional carbon composite (carbon-nanotube-interpenetrated mesoporous nitrogen-doped carbon spheres, MNCS/CNT), which can strongly adsorb lithium polysulfides, is now reported to act as a sulfur host. The nitrogen functional groups of this composite enable the effective trapping of lithium polysulfides on electroactive sites within the cathode, leading to a much improved electrochemical performance (1200 mAh g -1 after 200 cycles). The enhancement in adsorption can be attributed to the chemical bonding of lithium ions by nitrogen functional groups in the MNCS/CNT framework. Furthermore, the micrometer-sized spherical structure of the material yields a high areal capacity (ca. 6 mAh cm -2 ) with a high sulfur loading of approximately 5 mg cm -2 , which is ideal for practical applications of the lithium–sulfur batteries.

carbon materials↗
DOE OSTI2025

Cryptic cycling by electroactive bacterioplankton in Trout Bog Lake

The potential for extracellular electron transfer (EET) is a prevailing genomic feature of humic lake bacterioplankton. However, there has been little evidence for the substantial ecological contribution predicted by genetics. We hypothesized that anoxygenic phototrophic electrotrophs and accompanying heterotrophic electrogens cycle dissolved organic matter (DOM) between oxidized and reduced states. We predicted that such bacterioplankton would exhibit diel-scale oscillations due to the light dependency of photosynthesis. Using Trout Bog Lake in Wisconsin, USA, as our model ecosystem, we profiled the water column with depth-discrete metagenomic, physiochemical, and electrochemical analyses. We observed variation in oxidation reduction potential (ORP) in response to sunlight, initiating at depths populated by anoxygenic phototrophs with EET genes. We developed an automated buoy to measure electric current flow between many pairs of electrodes simultaneously, observing correlation in electron consumption to sunlight. Our results, combined with published metatranscriptomic analysis, indicate the occurrence of electron cycling between phototrophic oxidation (electrotrophic metabolism) by Chlorobium and anaerobic respiration (electrogenic metabolism) by Geothrix, involving DOM. We also repeatedly observed gradual seasonal increases in hypolimnion ORP throughout summer. These diel and seasonal patterns imply that electroactive DOM mediates the ecology of electroactive bacteria in lakes, controlling humic lake methane emissions.IMPORTANCEWe investigated the physical, chemical, and redox characteristics of a bog lake and electrodes hung therein to test the hypothesis that dissolved organic matter is being cycled between oxidized and reduced states by electroactive bacterioplankton powered by phototrophy. To do so, we performed field-based analyses on multiple timescales using both established and novel instrumentation. We paired these analyses with recently developed bioinformatics pipelines for metagenomics data to investigate genes that enable electroactive metabolism and accompanying metabolisms. Our results are consistent with our hypothesis and yet upend some of our other expectations. Our findings have implications for understanding greenhouse gas emissions from lakes, including electroactivity as an integral part of lake metabolism throughout more of the anoxic parts of lakes and for a longer portion of the summer than expected. Our results also give a sense of what electroactivity occurs at given depths and provide a strong basis for future studies.

carbon emissions↗
DOE OSTI2022

Chemical redox of lithium-ion solid electroactive material in a packed bed flow reactor

Chemical redox reactions between solid electroactive materials and dissolved electroactive compounds are a necessary component of emerging technologies relevant to renewable energy including high energy density flow batteries and battery material recycling. In this work, an initial investigation of heterogeneous chemical redox for a packed bed reactor configuration between solid electroactive material and dissolved redox shuttles will be described. Experimental conditions including the height of the packed bed, the redox shuttle solution concentration, solution flow rate, and operating temperature were varied and their impact on the molar conversion of the solid electroactive material in the packed bed was quantified using electroanalytical techniques on the reactor effluent. The progression of the reaction and its dependence on the different variables explored will be discussed in the context of the limiting processes for porous packed aggregates of the solid electroactive material undergoing chemical oxidation.

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

Coated electroactive materials

A process includes suspending an electroactive material in a solvent, suspending or dissolving a carbon precursor in the solvent; and depositing the carbon precursor on the electroactive material to form a carbon-coated electroactive material. Compositions include a graphene-coated electroactive material prepared from a solution phase mixture or suspension of an electroactive material and graphene, graphene oxide, or a mixture thereof.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Electroactive ZnO: Mechanisms, Conductivity, and Advances in Zn Alkaline Battery Cycling

Zinc oxide is of great interest for advanced energy devices because of its low cost, wide direct bandgap, non-toxicity, and facile electrochemistry. In zinc alkaline batteries, ZnO plays a critical role in electrode passivation, a process that hinders commercialization and remains poorly understood. Here, novel observations of an electroactive type of ZnO formed in Zn-metal alkaline electrodes are disclosed. The electrical conductivity of battery-formed ZnO is measured and found to vary by factors of up to 10 4 , which provides a first-principles-based understanding of Zn passivation in industrial alkaline batteries. Simultaneous with this conductivity change, protons are inserted into the crystal structure and electrons are inserted into the conduction band in quantities up to ≈10 20 cm –3 and ≈1 mAh gZnO –1 . Electron insertion causes blue electrochromic coloration with efficiencies and rates competitive with leading electrochromic materials. The electroactivity of ZnO is evidently enabled by rapid crystal growth, which forms defects that complex with inserted cations, charge-balanced by the increase of conduction band electrons. Furthermore, this property distinguishes electroactive ZnO from inactive classical ZnO. Knowledge of this phenomenon is applied to improve cycling performance of industrial-design electrodes at 50% zinc utilization and the authors propose other uses for ZnO such as electrochromic devices.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Electroactive compositions with poly(arylene oxide) and stabilized lithium metal particles

An electroactive composition includes an anodic material; a poly(arylene oxide); and stabilized lithium metal particles; where the stabilized lithium metal particles have a size less than about 200 .mu.m in diameter, are coated with a lithium salt, are present in an amount of about 0.1 wt % to about 5 wt %, and are dispersed throughout the composition. Lithium secondary batteries including the electroactive composition along with methods of making the electroactive composition are also discussed.

25 ENERGY STORAGE↗
DOE OSTI2014

Electroactive-Zone Extension in Flow-Battery Stacks

Flowable suspensions that conduct both electrons and ions can enable the use of energy-dense electroactive species in flow batteries [M. Duduta et al., Adv. Energy Mater., 1, 511 (2011); Z. Li et al., Phys. Chem. Chem. Phys., 15, 15,833 (2013); F. Fan et al., Nano Lett., 14, 2210 (2014)]. In comparison with conventional flow batteries where electrochemical reactions are confined to a fixed current-collector region, electronically conductive flow electrodes permit electrochemical reactions to extend outside of the physical confines of the stack. We have measured and modeled how mixed-conduction enables an electroactive zone (EAZ, in which electrochemical reactions occur) that is of greater spatial extent than current collectors, the extension being termed side zone, SZ. Electrochemical reactions in SZs can reduce coulombic and energetic efficiency. Here we show that for realistic suspension properties and operating conditions, the added inefficiency is small in practice, and can be further mitigated by using appropriate operating conditions and/or materials choices. For the specific example of a non-aqueous Li4Ti5O12 suspension, we show that EAZ extension contributes less than 1% additional efficiency loss at C/10 rates for current collectors greater than 20 mm long. (C) 2014 Elsevier Ltd. All rights reserved.

Smith, KC↗
DOE OSTI2022

Solute- and solvent-based electromotive force cells for activity measurements of electroactive species in molten salts

A novel combination of solute- and solvent-based electrodes was used to determine the activities of NdCl 3 and GdCl 3 in molten LiCI-KCI eutectic using electromotive force measurements across a broad concentration range of dissolved electroactive species. First, an electrochemical cell using solute-based electrodes was used to define the relative activity of each species as a function of concentration and the concentration region in which Henry's law was applicable. Next, the electromotive force between a solute-based electrode with a known NdCl 3 or GdCl 3 concentration and a solvent-based electrode with a known electromotive force was measured. The solvent-based electrode potential was converted to the Lithium Eutectic Electrode (LEE) potential, which allowed the activity of dissolved NdCl 3 and GdCl 3 to be calculated at the concentrations measured using the solute-based electrodes. The described two-cell method uses electromotive force measurements to accurately determine the activity of electroactive species over a wide concentration range and provides a simple approach to closing the knowledge gap of thermochemical properties of molten salts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Electroactive functional hybrid layered nanocomposites

Two methodologies to build new nanostructured hybrid layered nanocomposites are presented. The first one involves the preparation of hybrid metal/polymer nanolayers (NLs) by combining two monolayer preparation techniques: Horizontal Precipitation Langmuir Blodgett method (HP-ML), for copolymer monolayers and sputter deposition technique, for Au NLs deposition. The second methodology is aimed to prepare regular arrays of nanopores, with diameter ranging between 40-100 nm, in ultra-thin films of electroactive polymers, to obtain embedded regular arrays of nanopores filled by a further electroactive organic component. The produced hybrid MLs have been characterized by means of X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM) and Grazing Incidence X-ray Diffraction (GI-XRD). In the first case, current-voltage (I-V) measurements demonstrate that the multilayers exhibit a bipolar conduction behaviour (electrons and holes carriers), with a peculiar transition in the nature of the majority carriers (from holes to electrons) above a threshold number of bilayers. In the second case, it is found that the degree of pore filling, as well as the polymer crystallinity can be easily modulated, prompting the tuning of the photoresponse of the nanocomposites.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Long-Term Stability of Ferri-/Ferrocyanide as an Electroactive Component for Redox Flow Battery Applications: On the Origin of Apparent Capacity Fade

We assess the suitability of potassium ferri-/ferrocyanide as an electroactive species for long-term utilization in aqueous organic redox flow batteries. A series of electrochemical and chemical characterization experiments was performed to distinguish between structural decomposition and apparent capacity fade of ferri-/ferrocyanide solutions used in the capacity-limiting side of a flow battery. Our results indicate that, in contrast with previous reports, no structural decomposition of ferri-/ferrocyanide occurs at tested pH values as high as 14 in the dark or in diffuse indoor light. Instead, an apparent capacity fade takes place due to a chemical reduction of ferricyanide to ferrocyanide, via chemical oxygen evolution reaction. We find that this parasitic process can be further exacerbated by carbon electrodes, with apparent capacity fade rates at pH 14 increasing with an increased ratio of carbon electrode surface area to ferricyanide in solution. Based on these results, we report a set of operating conditions that enables the long-duration cycling of alkaline ferri-/ferrocyanide electrolytes and demonstrate how apparent capacity fade rates can be engineered by the initial system setup. If protected from direct exposure to light, the structural stability of ferri-/ferrocyanide anions allows for their practical deployment as electroactive species in long duration energy storage applications.

25 ENERGY STORAGE↗
DOE OSTI2015

Ionic electroactive polymer actuators as active microfluidic mixers

On-chip sample processing is integral to the continued development of lab-on-a-chip devices for various applications. An active microfluidic mixer prototype is proposed using ionic electroactive polymer actuators (IEAPAs) as artificial cilia. A proof-of-concept experiment was performed in which the actuators were shown to produce localized flow pattern disruptions in the laminar flow regime. Suggestions for further engineering and optimization of a scaled-down, complete device are provided. Furthermore, the device in its current state of development necessitates further engineering, the use of IEAPAs addresses issues currently associated with the use of electromechanical actuators as active microfluidic mixers and may prove to be a useful alternative to other similar materials.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Large-scale prediction of outer-membrane multiheme cytochromes uncovers hidden diversity of electroactive bacteria and underlying pathways

Multi-heme cytochromes (MHCs), together with accessory proteins like porins and periplasmic cytochromes, enable microbes to transport electrons between the cytoplasmic membrane and extracellular substrates (e.g., minerals, electrodes, other cells). Extracellular electron transfer (EET) has been described in multiple systems; yet, the broad phylogenetic and mechanistic diversity of these pathways is less clear. One commonality in EET-capable systems is the involvement of MHCs, in the form of porin-cytochrome complexes, pili-like cytochrome polymers, and lipid-anchored extracellular cytochromes. Here, we put forth MHCscan—a software tool for identifying MHCs and identifying potential EET capability. Using MHCscan, we scanned ~60,000 bacterial and 2,000 archaeal assemblies, and identify a diversity of MHCs, many of which represent enzymes with no known function, and many found within organisms not previously known to be electroactive. In total, our scan identified ~1,400 unique enzymes, each encoding more than 10 heme-binding motifs. In our analysis, we also find evidence for modularity and flexibility in MHC-dependent EET pathways, and suggest that MHCs may be far more common than previously recognized, with many facets yet to be discovered. We present MHCscan as a lightweight and user-friendly software tool that is freely available: https://github.com/Arkadiy-Garber/MHCscan.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2017

Soft Ionic Electroactive Polymer Actuators with Tunable Non-Linear Angular Deformation

The most rational approach to fabricate soft robotics is the implementation of soft actuators. Conventional soft electromechanical actuators exhibit linear or circular deformation, based on their design. This study presents the use of conjugated polymers, Poly(3,4- ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) to locally vary ion permeability of the ionic electroactive polymer actuators and manipulate ion motion through means of structural design to realize intrinsic angular deformation. Such angular deformations are closer to biomimetic systems and have potential applications in bio-robotics. Electrochemical studies reveal that the mechanism of actuation is mainly associated with the charging of electric double layer (EDL) capacitors by ion accumulation and the PEDOT:PSS layer’s expansion by ion interchange and penetration. Dependence of actuator deformation on structural design is studied experimentally and conclusions are verified by analytical and finite element method modeling. The results suggest that the ion-material interactions are considerably dominated by the design of the drop-cast PEDOT:PSS on Nafion.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Microtube-Membrane Methodology for Electrochemical Synthesis and Study of Electroactive and Ionically Conductive Materials, and the Conductivity of MnO 2

A membrane-based methodology for electrochemical synthesis and study of electroactive and ionically conductive materials is described. The Li + -intercalation material MnO 2 was used to demonstrate this methodology. The membrane was a polymeric support containing monodisperse gold microtubes (diameter 600 nm) that span the thickness of the membrane. Bipolar electrochemical synthesis of MnO 2 , from Mn 2+ solutions, was conducted across this membrane, resulting in deposition of monodisperse, hemispherical MnO 2 particles at the open ends of the tubes on one face of the membrane. The resulting microtube/MnO 2 composite membrane makes a convenient construct for investigating the transport properties of the MnO 2 particles. This was accomplished by mounting the membrane in a U-tube cell, placing electrolyte solutions on either side, and driving an ionic current through the membrane. The ionic conductivity of MnO 2 was measured in this way, and found to be 40±10 μS cm -1 when LiCl or LiClO 4 solutions were used as the electrolyte. Finally, the mechanism of ionic conductivity through these MnO 2 particles is discussed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Alluaudite Na 2 Co 2 Fe(PO 4 ) 3 as an electroactive material for sodium ion batteries

The electroactive orthophosphate Na 2 Co 2 Fe(PO 4 ) 3 was synthesized using a solid state reaction. Its crystal structure was solved using the combination of powder X-ray-and neutron-diffraction data. This material crystallizes according to the alluaudite structure (S.G. C 2/ c ). The structure consists of edge sharing [MO 6 ] octahedra (M = Fe, Co) resulting in chains parallel to [-101]. These chains are linked together via the [PO 4 ] tetrahedra to form two distinct tunnels in which sodium cations are located. The electrochemical properties of Na 2 Co 2 Fe(PO 4 ) 3 were evaluated by galvanostatic charge-discharge cycling. During the first discharge to 0.03 V, Na 2 Co 2 Fe(PO 4 ) 3 delivers a specific capacity of 604 mA h g (-1) . This capacity is equivalent to the reaction of more than seven sodium ions per formula unit. Hence, this is a strong indication of a conversion-type reaction with the formation of metallic Fe and Co. The subsequent charge and discharge involved the reaction of fewer Na ions as expected for a conversion reaction. When discharged to 0.9 V, the material intercalated only one Na+-ion leading to the formation of a new phase Na 3 Co 2 Fe(PO 4 ) 3 . This phase could then be cycled reversibly with an average voltage of 3.6 V vs. Na+/Na and a capacity of 110 mA h g (-1) . This result is in good agreement with the theoretical capacity expected from the extraction/insertion of two sodium atoms in Na 2 Co 2 Fe(PO 4 ) 3 .

25 ENERGY STORAGE↗
DOE OSTI2015

Nanocrystalline iron oxide based electroactive materials in lithium ion batteries: the critical role of crystallite size, morphology, and electrode heterostructure on battery relevant electrochemistry

The importance of crystallite size control and direct synthesis of materials with desirable properties is broadly applicable for the rational design and development of new active materials for energy storage. Recently, the use of nanoparticles and crystallite size control has redefined electrode design strategies, due in part to the large surface area/volume ratios providing more pathways for ion movement within the bulk electrode. This review is structured primarily as a case study, where reports involving a specific densely structured iron oxide, magnetite, Fe 3 O 4 , and its use as an electrode in LIBs are used as examples. Due to the high theoretical capacity (924 mA h g –1 ), and opportunity for implementation of a low cost electrode material, magnetite was selected as the model material for this review. Notably, crystallite size, morphology, and electrode heterostructure can all play a critical role in battery relevant electrochemistry, particularly for crystallographically dense materials such as Fe 3 O 4 . Several examples of Fe 3 O 4 based composites are described, incorporating different types of conductive materials such as carbons as part of the structure. Further, this review also provides a brief introduction to a newer iron oxide based material with a 2D layered structure, silver ferrite, where crystallite size control was synthetically achieved. By focusing on two specific iron oxide based nanoscale inorganic materials, this review highlights and distinguishes the contributions of electroactive material crystallite size, morphology and electrode heterostructure to electrochemical behavior, facilitating the future development of next generation of battery electrodes.

25 ENERGY STORAGE↗
DOE OSTI2018

Wavelength selective separation of metal ions using electroactive ligands

The separation of metal ions can be challenging because of similarities in charge density, size, and binding affinities. Here, we introduce a new photochemical separation strategy that relies on the intrinsically unique photophysical properties of metal ion complexes and the selective transformation of an electroactive ligand.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗