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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 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Mechanistic Insights into Surface Chemical Interactions between Lithium Polysulfides and Transition Metal Oxides

The design and development of materials for electrochemical energy storage and conversion devices requires fundamental understanding of chemical interactions at electrode/electrolyte interfaces. For Li–S batteries that hold the promise for outperforming the current generation of Li ion batteries, the interactions of lithium polysulfide (LPS) intermediates with the electrode surface strongly influence the efficiency and cycle life of the sulfur cathode. While metal oxides have been demonstrated to be useful in trapping LPS, the actual binding modes of LPS on 3d transition metal oxides and their dependence on the metal element identity across the periodic table remain poorly understood. Here, we investigate the chemical interactions between LPS and oxides of Mn, Fe, Co, and Cu by combining X-ray photoelectron spectroscopy and density functional theory calculations. We believe that Li–O interactions dominate LPS binding to the oxides (Mn 3 O 4 , Fe 2 O 3 , and Co 3 O 4 ), with increasing strength from Mn to Fe to Co. For Co 3 O 4 , LPS binding also involves metal–sulfur interactions. Moreover, we find that the metal oxides exhibit different binding preferences for different LPS, with Co 3 O 4 binding shorter-chain LPS more strongly than Mn 3 O 4 . In contrast to the other oxides, CuO undergoes intense reduction and dissolution reactions upon interaction with LPS. The reported findings are thus particularly relevant to the design of LPS/oxide interfaces for high-performance Li–S batteries.

25 ENERGY STORAGE↗
DOE OSTI2019

Upgraded Bioelectrocatalytic N 2 Fixation: From N 2 to Chiral Amine Intermediates

Enantiomerically pure chiral amines are of increasing value in the preparation of bioactive compounds, pharmaceuticals, and agrochemicals. ω-Transaminase (ω-TA) is an ideal catalyst for asymmetric amination because of its excellent enantioselectivity and wide substrate scope. To shift the equilibrium of reactions catalyzed by ω-TA to the side of the amine product, an upgraded N 2 fixation system based on bioelectrocatalysis was developed to realize the conversion from N 2 to chiral amine intermediates. The produced NH3 was in situ reacted with l-alanine dehydrogenase to generate alanine with NADH as a coenzyme. ω-TA transferred the amino group from alanine to ketone substrates and finally produced the desired chiral amine intermediates. The cathode of the upgraded N 2 fixation system supplied enough reducing power to synchronously realize the regeneration of reduced methyl viologen (MV •+ ) and NADH for the nitrogenase and l-alanine dehydrogenase. The coproduct, pyruvate, was consumed by l-alanine dehydrogenase to regenerate alanine and push the equilibrium to the side of amine. After 10 h of reaction, the concentration of 1-methyl-3-phenylpropylamine achieved 0.54 mM with the 27.6% highest faradaic efficiency and >99% enantiomeric excess (eep). Because of the wide substrate scope and excellent enantioselectivity of ω-TA, the upgraded N2 fixation system has great potential to produce a variety of chiral amine intermediates for pharmaceuticals and other applications.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2026

Preparation of a uranium monocarbide anode and electrochemical characterization in molten LiCl-KCl-UCl 3

Porous uranium carbide (UC) pellets possessing moderate electrical conductivity were synthesized by reaction of UO 2 with graphite at temperatures up to 1550°C under rough vacuum. Conversions as high as 98% were achieved at soak times of 2-4 hours. The electrochemistry of the UC pellets in molten LiCl-KCl-6.5 wt% UCl 3 was explored using a variety of techniques including DC polarization methods, cyclic voltammetry, chronopotentiometry and bulk electrolysis. Here, the electrode reaction for anodic dissolution was found to be kinetically controlled by dissociation of UC to a transition state complex that was hypothesized to consist of a uranium atom partially complexed by chloride ions. Precise measurements of current efficiencies using chronopotentiometry indicated upper limits of 90.9 ± 3.4% and 98.3 +1.7/-3.7% for anode and cathode, respectively, when operating at anodic overpotentials near +300 mV. Bulk electrolysis of a UC pellet performed by passing 98% of the theoretical charge resulted in nearly complete recovery of its uranium content as highly pure metal at the cathode.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Understanding Water Transport in Polymer Electrolyte Fuel Cells Using Coupled Continuum and Pore-Network Models

Water management remains a critical issue for polymer electrolyte fuel cell performance and durability, especially at lower temperatures and with ultrathin electrodes. To understand and explain experimental observations better, water transport in gas diffusion layers (GDLs) with macroscopically heterogeneous morphologies was simulated using a novel coupling of continuum and pore-network models. X-ray computed tomography was used to extract GDL material parameters for use in the pore-network model. The simulations were conducted to explain experimental observations associated with stacking of anode GDLs, where stacking of the anode GDLs increased the limiting current density. Through imaging, it is shown that the stacked anode GDL exhibited an interfacial region of high porosity. The coupled model shows that this morphology allowed more efficient water movement through the anode and higher temperatures at the cathode compared to the single GDL case. As a result, the cathode exhibited less flooding and hence better low temperature performance with the stacked anode GDL.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2016

Automotive Lithium-ion Cell Manufacturing: Regional Cost Structures and Supply Chain Considerations

Manufacturing capacity for lithium-ion batteries (LIBs)--which power many consumer electronics and are increasingly used to power electric vehicles--is heavily concentrated in east Asia. Currently, China, Japan, and Korea collectively host 88% of all LIB cell and 79% of automotive LIB cell manufacturing capacity. Mature supply chains and strong cumulative production experience suggest that most LIB cell production will remain concentrated in Asia. However, other regions--including North America--could be competitive in the growing automotive LIB cell market under certain conditions. To illuminate the factors that drive regional competitiveness in automotive LIB cell production, this study models cell manufacturing cost and minimum sustainable price, and examines development of LIB supply chains and current LIB market conditions. Modeled costs are for large format, 20-Ah stacked pouch cells with lithium-nickel-manganese-cobalt-oxide (NMC) cathodes and graphite anodes suitable for automotive application. Production volume is assumed to be at commercial scale, 600 MWh per year.

25 ENERGY STORAGE↗
DOE OSTI2015

Electrode design for low temperature direct-hydrocarbon solid oxide fuel cells

In certain embodiments of the present disclosure, a solid oxide fuel cell is described. The solid oxide fuel cell includes a hierarchically porous cathode support having an impregnated cobaltite cathode deposited thereon, an electrolyte, and an anode support. The anode support includes hydrocarbon oxidation catalyst deposited thereon, wherein the cathode support, electrolyte, and anode support are joined together and wherein the solid oxide fuel cell operates a temperature of 600.degree. C. or less.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2016

Final Report: Cathode Catalysis in Hydrogen/Oxygen Fuel Cells: New Catalysts, Mechanism, and Characterization

In this research, we prosecuted a comprehensive plan of research directed at developing new catalysts and new understandings relevant to the operation of low temperature hydrogen-oxygen fuel cells. The focal point of this work was one centered on the Oxygen Reduction Reaction (ORR), the electrochemical process that most fundamentally limits the technological utility of these environmentally benign energy conversion devices. Over the period of grant support, we developed new ORR catalysts, based on Cu dimers and multimers. In this area, we developed substantial new insight into design rules required to establish better ORR materials, inspired by the three-Cu active site in laccase which has the highest ORR onset potential of any material known. We also developed new methods of characterization for the ORR on conventional (metal-based) catalysts. Finally, we developed a new platform to study the rate of proton transfer relevant to proton coupled electron transfer (PCET) reactions, of which the ORR is an exemplar. Other aspects of work involved theory and prototype catalyst testing.

08 HYDROGEN↗
DOE OSTI2024

Photoelectrochemical CO 2 Reduction to CO Enabled by a Molecular Catalyst Attached to High-Surface-Area Porous Silicon

A high-surface-area p-type porous Si photocathode containing a covalently immobilized molecular Re catalyst is highly selective for the photoelectrochemical conversion of CO 2 to CO. It gives Faradaic efficiencies of up to 90% for CO at potentials of –1.7 V (versus ferrocenium/ferrocene) under 1 sun illumination in an acetonitrile solution containing phenol. Here, the photovoltage is approximately 300 mV based on comparisons with similar n-type porous Si cathodes in the dark. Using an estimate of the equilibrium potential for CO 2 reduction to CO under optimized reaction conditions, photoelectrolysis was performed at a small overpotential, and the onset of electrocatalysis in cyclic voltammograms occurred at a modest underpotential. The porous Si photoelectrode is more stable and selective for CO production than the photoelectrode generated by attaching the same Re catalyst to a planar Si wafer. Further, facile characterization of the porous Si-based photoelectrodes using transmission mode FTIR spectroscopy leads to highly reproducible catalytic performance.

14 SOLAR ENERGY↗
DOE OSTI2022

Half-cell electrode assessments of a crossover-tolerant direct methanol fuel cell with a platinum group metal-free cathode

In this work, a platinum group metal- free (PGM-free) Fe-N-C oxygen reduction reaction (ORR) catalyst derived from metal organic framework precursors (Fe-MOF) is evaluated at the cathode side of a direct methanol fuel cell (DMFC). A wide range of methanol concentrations were used, and the performance of the DMFC using air was evaluated and compared to a commercial Pt/C cathode. We conducted our tests with a custom, integrated H 2 reference electrode that separately provided the anode and cathode overpotentials. This allowed us to perform a Tafel analysis on both electrodes and understand the dominant polarizations involved at the PGM-free cathode and the PtRu/C anode. Overall, we achieved a high cell performance using a Fe-N-C based catalyst under liquid methanol and air operation with a peak power density of 111 mW/cm 2 , where the cathode presented a markedly larger contribution to the voltage loss versus the anode. Additionally, we used nanoscale X-ray computed tomography (nano-CT) to image the Fe-N-C cathode and investigate the ionomer and pore size distributions allowing us to identify areas of improvement for catalyst layer fabrication.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2017

Insights on the extraordinary tolerance to alcohols of Fe-N-C cathode catalysts in highly performing direct alcohol fuel cells

Direct alcohol fuel cells (DAFCs) represent the best alternative to batteries for portable and auxiliary power units application due to the high energy density of short chain alcohols. Currently, the utilization of the best platinum group metal (PGM) cathode catalysts is limited, not only by a high cost and scarce resources, but also by the inefficient oxygen reduction reaction (ORR) when permeated alcohols adsorb on the catalytic active sites. In this work, a highly active Fe-N-C catalyst derived from the pyrolysis of nicarbazin (a nitrogen charge transfer organic salt) and an iron precursor has been investigated to get insights on the extraordinary tolerance to the presence of alcohols (methanol and ethanol) of such a PGM-free catalyst. Density functional theory (DFT) calculations demonstrate for the first time that Fe-N 4 and Fe-N 2 C 2 active sites preferentially adsorb oxygen with much higher energy than methanol, ethanol and products of partial ethanol oxidation (0.73–1.16 eV stronger adsorption), while nitrogen-carbon related sites (pyridinic and graphitic nitrogen) are much less selective towards ORR. Half-cell electrochemical characterization showed that the Fe-N-C catalyst overcomes Pt ORR activity in acidic medium with methanol or ethanol concentrations as low as 0.01 M. The feasibility of DAFCs operation based on high methanol (up to 17 M) and ethanol (up to 5 M) concentration thanks to the utilization of Fe-N-C cathode catalyst is demonstrated. Lastly, a new strategy is proposed for DAFCs where using Pt only at the anode and Fe-N-C at the cathode allows extending the device energy density compared to PGM-based catalysts at both electrodes.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2019

Electrodeposition of Nanostructured Copper on Gas Diffusion Layers as Electrocatalysts for Carbon Dioxide Reduction

The aim of the summer project was to immobilize copper nanostructures on gas diffusion layers to serve as electrocatalysts for the electrochemical reduction of CO 2 . Gas diffusion layers are typically bilayer structures consisting of a macro-porous backing material (carbon fiber paper) and a microporous, carbon-based layer (MPL). Classically, the copper catalysts are loaded on the microporous layer. Furthermore, the GDL is intrinsically hydrophobic due to polytetrafluoroethylene (PTFE)in its chemical composition, with the MPL having a more hydrophobic character due to its higher PTFE content. While beneficial for rendering the MPL impervious to electrolytes during actual CO 2 reduction, the hydrophobicity precludes sufficient wetting of the MPL layer, preventing conformal, uniformly distributed and strongly adhered deposits. A two electrode electrodeposition system was used to facilitate copper deposition. An implication of this system is the inability to ascertain or accurately modulate the cathodic over-potential. Hence, galvanostatic (current control) procedures are utilized for all deposition. To improve the wetting behavior of the MPL, the surface is subjected to surface pretreatment protocols prior to electrodeposition. In addition, as morphology of deposits play a role in their efficacy as catalysts in terms of selectivity and conversion, we systematically investigate the effects of different galvanostatic deposition procedures on copper morphology.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Spontaneous Lithiation of Binary Oxides during Epitaxial Growth on LiCoO 2

Epitaxial growth is a powerful tool for synthesizing heterostructures and integrating multiple functionalities. Interfacial mixing can readily occur at temperatures required for complete film crystallization and can significantly modify the properties of layered structures, particularly for those containing energy storage materials with smaller cations. Here we show a two-step sequence involving the growth of an epitaxial LiCoO 2 cathode layer followed by the deposition of a binary transition metal oxide (WO 3 , TiO 2 , and others) in which controlled lithiation of the binary oxide occurs. Orientation-controlled epitaxial synthesis of the model solid-state-electrolyte Li 2 WO 4 and model anode material Li 4 Ti 5 O 12 occurs as WO 3 and TiO 2 nucleate their respective host lattices and attract Li ions from the underlying cathode. The cathode layer readily provides a tunable amount of Li ions for the controlled lithiation of the subsequent layer. We demonstrate that this approach can be used for energy materials discovery and exploring different combinations of epitaxial interfaces that can serve as well-defined model systems for mechanistic studies of energy storage and conversion processes.

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

Meshfree Methods for Modeling Chemo-Mechanical Cathode Cracking in Li-Ion Batteries

Through repeated charging and discharging, the electrodes of a Li-ion battery experience cyclic loading causing swelling and contraction due to the movement of lithium, also known as intercalation. This research focuses specifically on the chemo-mechanical cracking in the cathode. Because cathode particles are comprised of many randomly-oriented grains, which have highly anisotropic material properties, the expansion and contraction is very non-uniform. As a result, stress concentrations tend to form between grains, which necessitates the modeling of crack propagation largely along grain boundaries. Chemo-mechanical models are simulated mainly by two methods: the cohesive zone model (CZM) and the continuous damage model (CDM). The CZM is more accurate at capturing the sharp discontinuities of a crack but is very computationally expensive and intractable for large-scale models as a result. Conversely, the CDM is easily computed but not well-suited to easily allow for discontinuous field variables, which are inherent across a crack. This study aims to improve the CDM's ability to capture discontinuous cracks. Current versions of the CDM use the finite element method (FEM), which is one of the most widely used approaches for spatial discretization. This research investigates the use of the Reproducing Kernel Particle Method (RKPM), a meshfree method, for spatial discretization and aims to achieve a chemo-mechanical crack propagation model that achieves both intermediate accuracy and computational time between a CDM and CZM. To gain a better understanding of how the meshfree model compares to the current FEM model in capturing cathode crack propagation, further investigation is needed.

cathode cracking↗
DOE OSTI2016

A Nitrogen-Doped Carbon Catalyst for Electrochemical CO 2 Conversion to CO with High Selectivity and Current Density

We report characterization of a non-precious metal-free catalyst for the electrochemical reduction of CO 2 to CO; namely, a pyrolyzed carbon nitride and multiwall carbon nanotube composite. This catalyst exhibits a high selectivity for production of CO over H 2 (approximately 98 % CO and 2 % H 2 ), as well as high activity in an electrochemical flow cell. The CO partial current density at intermediate cathode potentials (V=-1.46 V vs. Ag/AgCl) is up to 3.5× higher than state-of-the-art Ag nanoparticle-based catalysts, and the maximum current density is 90 mA cm -2 . The mass activity and energy efficiency (up to 48 %) were also higher than the Ag nanoparticle reference. Moving away from precious metal catalysts without sacrificing activity or selectivity may significantly enhance the prospects of electrochemical CO 2 reduction as an approach to reduce atmospheric CO 2 emissions or as a method for load-leveling in relation to the use of intermittent renewable energy sources.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Amorphous Manganese Oxides: An Approach for Reversible Aqueous Zinc-Ion Batteries

Crystalline manganese oxides have attracted the most attention in aqueous zinc-ion batteries due to their diverse nanostructures and low cost. However, extensive studies on amorphous manganese oxides are lacking. Here in this paper, we report a mesoporous amorphous manganese oxide (UCT-1-250) as a cathode material with high capacity (222 mAh g –1 ), good cyclability (57% capacity retention after 200 cycles), and an acceptable discharge plateau (between 1.2 and 1.4 V). An approach to mechanistic studies was performed by comparison of UCT-1-250 and other crystalline manganese oxides through electrochemical, elemental, and structural analyses. An in situ conversion to ZnMn 2 O 4 spinel phase after initial cycling contributes to the high performance. The irreversible capacity fading is due to the formation of the woodruffite phase.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Continuous production of pure liquid fuel solutions via electrocatalytic CO 2 reduction using solid-electrolyte devices

Electrocatalytic CO 2 reduction is often carried out in a solution electrolyte such as KHCO 3 (aq), which allows for ion conduction between electrodes. Thus, liquid products that form are in a mixture with the dissolved salts, requiring energy-intensive downstream separation. In this work, we report continuous electrocatalytic conversion of CO 2 to pure liquid fuel solutions in cells that utilize solid electrolytes, where electrochemically generated cations (such as H+) and anions (such as HCOO–) are combined to form pure product solutions without mixing with other ions. Using a HCOOH-selective (Faradaic efficiencies>90%) and easily scaled Bi catalyst at the cathode, we demonstrate production of pure HCOOH solutions with concentrations up to 12M. We also show 100h continuous and stable generation of 0.1 M HCOOH with negligible degradation in selectivity and activity. Production of other electrolyte-free C 2+ liquid oxygenate solutions, including acetic acid, ethanol and n-propanol, are also demonstrated using a Cu catalyst. Lastly, we show that our CO 2 reduction cell with solid electrolytes can be modified to suit other, more complex practical applications.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Cassettes for solid-oxide fuel cell stacks and methods of making the same

Solid-oxide fuel cell (SOFC) stack assembly designs are consistently investigated to develop an assembly that provides optimal performance, and durability, within desired cost parameters. A new design includes a repeat unit having a SOFC cassette and being characterized by a three-component construct. The three components include an oxidation-resistant, metal window frame hermetically joined to an electrolyte layer of a multi-layer, anode-supported ceramic cell and a pre-cassette including a separator plate having a plurality of vias that provide electrical contact between an anode-side collector within the pre-cassette and a cathode-side current collector of an adjacent cell. The third component is a cathode-side seal, which includes a standoff that supports a cathode channel spacing between each of the cassettes in a stack. Cassettes are formed by joining the pre-cassette and the window frame.

30 DIRECT ENERGY CONVERSION↗