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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 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Integrated Experimental and Computational K-Edge X-ray Absorption Near-Edge Structure Analysis of Vanadium Catalysts

X-ray Absorption Near-Edge Structure (XANES) spectroscopy is a powerful tool to reveal key structural and electronic features of isolated catalytic sites, yet insights into molecular structure and more detailed orbital analysis through a combination of experimental and computed XANES analysis are necessary for accurate interpretation of the spectra, especially when significant heterogeneity exits among the catalytic sites. Herein, we present an integrated computational and experimental strategy to determine both primary and secondary bonding interactions within the XANES pre-edge region for organovanadium complexes, which was developed using a series of well-defined molecular vanadium complexes and then applied to the characterization of a supported organovanadium olefin hydrogenation catalyst. Time-dependent density functional theory is used to predict the energy of pre-edge XANES features for a series of vanadium complexes with a variety of oxidation states and local coordination environments. Further, a calibration scheme incorporating different density functionals and basis sets is established, resulting in an optimized scheme that accurately predicts pre-edge energies with a mean absolute error of 0.40 eV. Second-shell coordination (e.g., V---V) effects within XANES are identified through the analysis of the computed dominant orbital contributions for multi-vanadium complexes. Orbital analysis also provided confirmation that the vanadium-hydride formation combined with the heterogeneity of the catalytic active species in ole-fin hydrogenation caused the energy shift and broadening of the pre-edge peak after hydrogen treatment of the silica-supported organovanadium pre-catalyst. This work further elucidates computational XANES simulations and techniques potentially guiding characterization in surface organometallic chemistry.

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

Development and Characterization of Electrodes for Surface-Specific Attenuated Total Reflection Two-Dimensional Infrared Spectroelectrochemistry

Electrochemical interfaces still have remaining mysteries surrounding the interfacial region of the electrical double layer, despite being prevalent throughout the energy and water remediation industries. The electrical double layer is where many important dynamic processes such as catalysis and electron transfer occur. The goal of this work is to study the electrical double layer with two-dimensional infrared (2D IR) spectroscopy to experimentally access the details of the structural dynamics of this complex environment. However, there are several experimental challenges to applying 2D IR spectroscopy to this application, such as assuring the surface specificity of the spectrum, optimizing the signal strength while minimizing spectral distortions from dispersion and Fano line shapes, and selecting electrode materials that are both sufficiently IR compatible and conductive. Here we will discuss various considerations when designing 2D IR experiments of electrode interfaces utilizing several substrates and experimental configurations and demonstrate a robust method for 2D IR experiments of electrode interfaces under applied potential that combines nonconducting Si ATR wafers with conductive ITO and thin nanostructured films of plasmonically active Au functionalized with 3-mercapto-2-butanone (MCB). We show that layered electrodes on thin Si ATR wafers with MCB are sensitive to applied potential and that the distortions in the linear and 2D IR spectra are heavily dependent on the morphology of the Au surface.

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

Enhancing Four-Carbon Olefin Production from Acetylene over Copper Nanoparticles in Metal–Organic Frameworks

Four-carbon olefins, such as 1-butene and 1,3-butadiene, are important chemical feedstocks for the production of adhesives and synthetic rubber. These compounds are found in the C 4 fraction of “green oil” products that can arise during the hydrogenation of acetylene. Here, we demonstrate that control of the catalyst structure increases the yield and productivity of these important olefins with a family of catalyst materials comprising Cu nanoparticles (CuNPs) bound within the pores of Zr-based metal–organic frameworks. Using carbon monoxide as a probe molecule, we characterize the surfaces of these catalytic CuNPs with diffuse reflectance infrared Fourier transform spectroscopy, revealing that the electronic structure of the CuNP surfaces is size-dependent. Furthermore, we find that as the CuNP diameter decreases, the selectivity for C 4 products increases and that lowering the stoichiometric ratio of H 2 /acetylene improves the selectivity and productivity of the catalyst.

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

Comparison of Heterogeneous Hydroformylation of Ethylene and Propylene over RhCo 3 /MCM-41 Catalysts

The reaction mechanisms of heterogenous hydroformylation of ethylene and propylene were compared at 413-453 K using RhCo 3 /MCM-41 as catalysts. The reaction rates of propylene for both hydroformylation and the undesired side reaction of hydrogenation were found to be about one order of magnitude lower than those for ethylene in flow reactor studies. The difference in the kinetic behavior between ethylene and propylene was investigated by measuring the reaction orders and apparent activation energies, and these macro-kinetic observables were analyzed using the degree of rate control (DRC) method. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) experiments were performed to characterize the surface intermediates formed during the reactions. When the reactant was changed from ethylene to propylene, the IR peak corresponding to adsorbed CO exhibited a significant increase, while the IR peaks of alkyl group decreased in magnitude. Combined with the DRIFTS results, DRC analysis indicates that the first step of olefin hydroformylation, the formation of an alkyl group on the catalyst surface, plays a key role in the difference between ethylene and propylene. This step is kinetically non-relevant when ethylene is the reactant, but it is one of the rate-controlling steps for propylene. Furthermore, the low concentration of the adsorbed propyl group, which is a common intermediate shared by both hydroformylation and hydrogenation of propylene, decreases the rates of both reaction pathways as compared to ethylene.

10 SYNTHETIC FUELS↗
DOE OSTI2025

Tracking Local pH Dynamics during Water Electrolysis via In-Line Continuous Flow Raman Spectroscopy

The performance of electrochemical devices, which play a critical role in decarbonization efforts, is often governed by proton-coupled electron transfer reactions at the electrode–electrolyte interface. These reactions are highly sensitive to the complex and dynamic microenvironment present at the electrode surface. However, characterizing this environment─particularly monitoring interfacial pH and its evolution under reaction conditions─remains challenging, necessitating the development of advanced analytical tools. Here, in this study, we introduce in-line continuous flow Raman spectroscopy (CFRS) as a spectroelectrochemical platform for quantifying interfacial pH swings generated during water-splitting. By monitoring phosphate ion speciation and controlling the hydrodynamics with a flow cell, we measure pH swings as a function of current density, flow rate, and distance from the electrode. Comparison with theoretical models reveals the impact of bulk pH, boundary layer thickness, and bubble dynamics at high current densities. Collectively, these findings establish CFRS as a platform for quantitatively investigating pH dynamics, offering critical insights for advancing electrochemical energy conversion technologies.

Marquez, Raul A. [Univ. of Texas, Austin, TX (Unit↗
DOE OSTI2026

Pseudo–Jahn–Teller Distortion in a One-Dimensional π-Conjugated Polymer

Structural distortions in low-dimensional π-conjugated systems profoundly influence their electronic properties, but the control of such behavior in laterally extended systems remains challenging. Here, in this study, we demonstrate that a one-dimensional conjugated polymer─ poly -(difluorenoheptalene-ethynylene) (PDFHE)─undergoes a pronounced out-of-plane backbone distortion, equivalent to a spontaneous symmetry breaking (SSB) of its mirror symmetry. We synthesized PDFHE on noble metal surfaces and characterized its structure and electronic states using low-temperature scanning tunneling microscopy (STM). Rather than adopting a planar, high-symmetry conformation, PDFHE relaxes into nonplanar isomers stabilized by a pseudo–Jahn–Teller (PJT) distortion having mirror-odd out-of-plane character. The distortion lowers the total energy and increases the band gap, providing a concise rationale for the observed symmetry breaking. Density functional theory calculations corroborate these findings, providing a microscopic explanation for the SSB. Our results show that even in mechanically robust extended π-systems, subtle electron–lattice coupling can spontaneously drive significant structural rearrangements, even in mechanically robust extended π-systems.

conformation↗
DOE OSTI2021

macroMS: Image-Guided Analysis of Random Objects by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry

Mass spectrometry imaging is well-suited to characterizing sample surfaces for their chemical content in a spatially resolved manner. However, when the surface contains small objects with significant empty spaces between them, more efficient approaches to sample acquisition are possible. Image-guided mass spectrometry (MS) enables high-throughput analysis of a diverse range of sample types, such as microbial colonies, liquid microdroplets, and others, by recognizing and analyzing selected location targets in an image. Here, we describe an imaging protocol and macroMS, an online software suite that can be used to enhance MS measurements of macroscopic samples that are imaged by a camera or a flatbed scanner. Furthermore, the web-based tool enables users to find and filter targets from the optical images, correct optical distortion issues for improved spatial location of selected targets, input the custom geometry files into an MS device to acquire spectra at the selected locations, and finally, perform limited data analysis and use visualization tools to aid locating samples containing compounds of interest. Using the macroMS suite, an enzyme mutant library of Saccharomyces cerevisiae and nL droplet arrays of Escherichia coli and Pseudomonas fluorescens have been assayed at a rate of ~2 s/sample.

47 OTHER INSTRUMENTATION↗
DOE OSTI2023

Southern Ocean Low Cloud and Precipitation Phase Observed During the Macquarie Island Cloud and Radiation Experiment (MICRE)

Shallow cloud decks residing in or near the boundary layer cover a large fraction of the Southern Ocean (SO) and play a major role in determining the amount of shortwave radiation reflected back to space from this region. In this article, we examine the macrophysical characteristics and thermodynamic phase of low clouds (tops <3 km) and precipitation using ground-based ceilometer, depolarization lidar and vertically-pointing W-band radar measurements collected during the Macquarie Island Cloud and Radiation Experiment (MICRE) from April 2016 to March 2017. During MICRE, low clouds occurred ~65% of the time on average (slightly more often in austral winter than summer). About 2/3 of low clouds were cold-topped (temperatures ≤0°C). These were thicker and had higher bases on average than warm-topped clouds. 83%–88% of cold-topped low clouds were liquid phase at cloud base (depending on the season). The majority of low clouds had precipitation in the vertical range 150–250 m below cloud base, a significant fraction of which did not reach the surface. Phase characterization is limited to the period between April 2016 and November 2016. Small-particle (low-radar-reflectivity) precipitation (which dominates precipitation occurrence) was mostly liquid below-cloud, while large-particle precipitation (which dominates total accumulation) was predominantly mixed/ambiguous or ice phase. Approximately 40% of cold-topped clouds had mixed/ambiguous or ice phase precipitation below (with predominantly liquid phase cloud droplets at cloud base). Below-cloud precipitation with radar reflectivity factors below about -10 dBZ were predominantly liquid, while reflectivity factors above about 0 dBZ were predominantly ice.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Electrochemical corrosion of multiphase stainless steel-based alloy nuclear waste forms

Abstract The electrochemical corrosion behaviors of two multiphase alloys representing waste forms made with 316 L stainless steel and different amounts of surrogate metallic fuel wastes were measured and related to the microstructures. Potentiodynamic (PD) scans were performed in an acid brine solution and the corroded surfaces were characterized with scanning electron microscopy (SEM) to compare the electrochemical responses to the corrosion of specific phases. PD scans for the two multiphase alloys, 316 L stainless steel, and pure palladium were compared to understand the complex corrosion behavior of these multiphase alloys also recently classified as multi principle element alloys (MPEAs) and to determine the effects of alloying elements and noble metals present in constituent phases on the corrosion behavior.

Gattu, Vineeth Kumar (ORCID:0000000307265813)↗
DOE OSTI2024

Statistical characterization of high voltage vacuum surface flashover with gapped and ungapped anodes

This manuscript reports the experimental study of a novel vacuum high-voltage (HV) feedthrough geometry with a recessed anode triple junction (ATJ) relevant to large-scale pulsed power systems. It is shown experimentally that introducing a vacuum gap between the insulator–anode interface and recessing the ATJ farther away from the cathode triple junction significantly enhances high voltage (HV) vacuum surface flashover hold-off. The results for “first pulse” and “consecutive pulse” tests are reported. The physical mechanisms contributing to the electrical failure of this feedthrough geometry appear to be unique to this geometry. These findings show the potential to allow for HV vacuum surface flashover geometries with significantly improved electrical characteristics.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

Active site identification and CO oxidation in UiO-66-XX thin films

Metal-organic frameworks (MOFs) offer an intrinsically porous and chemically tunable platform for gas adsorption, separation, and catalysis. Herein we investigate thin film derivatives of the well-studied Zr–O based MOF powders to understand their adsorption properties and reactivity with their adaption to thin films, involving diverse functionality with the incorporation of different linker groups and the inclusion of embedded metal nanoparticles: UiO-66, UiO-66-NH 2 , and Pt@UiO-66-NH 2 . Using transflectance IR spectroscopy, we determine the active sites in each film upon consideration of the acid-base properties of the adsorption sites and guest species, and perform metal-based catalysis with CO oxidation of a Pt@UiO-66-NH 2 film. Our study shows how surface science characterization techniques can be used to characterize the reactivity and the chemical and electronic structure of MOFs.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Nontrivial Fermi surface topology of the kagome superconductor CsV 3 Sb 5 probed by de Haas–van Alphen oscillations

Here, we have investigated the normal state Fermi-surface properties of the kagome superconductor CsV 3 Sb 5 using torque magnetometry with applied fields (H) up to 35 T. The torque signal shows clear de Haas-van Alphen (dHvA) oscillations above 15 T. The oscillations are smooth and consist of seven distinct frequencies with values from similar to ~18 T to 2135 T. The presence of higher frequencies in CsV 3 Sb 5 is further confirmed by carrying out additional measurements using the tunnel diode oscillator technique. All frequencies measured at different tilt angles (θ) of the field direction with respect to the c axis show a 1/cosθ dependence, implying that the Fermi surfaces corresponding to these frequencies are two dimensional (2D). The absence of dHvA oscillations at θ = 90° further supports the presence of 2D Fermi surfaces. The Berry phase (φ) determined from the Landau level fan diagram for all frequencies is similar to ~ 0.4. This value is close to the theoretical value of φ = 0.5 for a nontrivial system, which strongly supports the nontrivial topology of the Fermi surfaces of these frequencies. Several quantities characterizing the Fermi surface are calculated employing the Lifshitz-Kosevich theory. These findings are crucial for exploring the interplay between nontrivial band topology, charge-density wave, and unconventional superconductivity of CsV 3 Sb 5 .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Antimony Chloride Treatments of CdTe-Based Solar Cells

Development of a new SbCl3-based solution treatment for chloride activation of CdTe-based solar cells is described. Activation was confirmed with CdSeTe:Sb devices exhibiting VOC > 550 mV and JSC > 25 mAcm-2. Treatment optimization showed strong effects of annealing time and temperature on cell properties. Material characterization indicated surface conversion of CdSeTe to CdCl2 and Sb2Te3 with SbCl3 treatment. However, no reaction products were formed with treatment under inert conditions, which was coupled with poor device performance. Drying the SbCl3 films at controlled humidity conditions confirmed that exposure to high relative humidity is critical for CdSeTe activation, through hydrolysis of SbCl3. Mechanistic details of SbCl3 speciation during hydrolysis and annealing to activate CdSeTe are discussed.

14 SOLAR ENERGY↗
DOE OSTI2021

Melting and Ejecta Produced by High Velocity Microparticle Impacts of Steel on Tin

At sufficiently high velocities, a microparticle impacting a metal substrate can cause ejection of material from the substrate and impact-induced melting, both of which can result in erosion. Here, we directly image the impact of individual hard steel microparticles on soft tin substrates, at controlled impact velocities in the range of ~100 to 1000 m/s. By using scanning electron and laser scanning confocal microscopy, we characterize the surface morphology, depth, and volume of each impact crater. We observe a gradual onset of impact-induced melting in the craters, as well as the production of increasing amounts of ejecta from the target metal. By comparing measurements of impact and rebound velocity to an elastic-plastic model, we observe that at a high enough impact velocity, melting and ejection begin to consume additional kinetic energy beyond that expected by plastic deformation of the target material alone. By calculating the excess energy dissipation using this elastic-plastic model, we show that although this divergent behavior is associated with the onset of melting, the majority of the ejected volume must be solid rather than liquid.

Mechanics↗
DOE OSTI2025

Additive Manufacturing of Lattice Structures for Catalyst Applications

Abstract The design and fabrication of Inconel 718 open-pore lattice structures via Laser Powder Bed Fusion (LPBF) has been investigated in this research, focusing on applications such as catalyst supports in jet fuel production. The study explores the impact of laser power and scanning speed on the geometrical resolution of these structures aiming to achieve high porosity (porosity > 60%) and specific pore sizes ranging from 500–1000 μm, intending to serve as catalyst supports, replacing conventionally manufactured foams to reduce costs. Results demonstrate the significant influence of processing parameters on the geometrical aspects of printed lattice structures, with laser power having a more pronounced effect on geometrical accuracy than scanning speed. Additionally, the mechanical properties of the printed lattice structures showed a correlation with the lattice strut sizes, as lattices with less porosity and thicker struts resulted in higher maximum shear stress.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Structural Analysis of K 4 Fe(CN) 6 ·3H 2 O, K 3 Fe(CN) 6 and Prussian Blue

XRD and XAS were used to characterize the bulk structure, while XPS was used to characterize the surface structure, of commercially obtained nominally K 4 Fe(CN) 6 ·3H 2 O, K 3 Fe(CN) 6 and our synthesized Prussian Blue (PB) material. K 4 Fe(CN) 6 ·3H 2 O was found to consist of a fully hydrated phase, which crystallizes in the monoclinic form and a less hydrated or anhydrous phase which crystallizes in the orthorhombic form. K 3 Fe(CN) 6 was found to consist of the well-established orthorhombic form rather than the monoclinic form. The structure of our synthesized Prussian Blue (PB) was found to be consistent with that reported for (KOH) 0.7 Fe(III) 1.33 Fe(II)(CN) 6 ·4.0H 2 O which crystallizes in the cubic form. XPS and XAS confirmed the presence of ferrous Fe(II) at the surface and bulk levels in K 4 Fe(CN) 6 ·xH 2 O. However, XPS revealed the presence of Fe(II) (~30%) and Fe(III) (~70%) in the surface region of K 3 Fe(CN) 6 while XAS confirmed the presence of mostly Fe(III) at the bulk level. Both XPS and XANES confirmed the presence of Fe(II) and Fe(III) in the surface and bulk regions of PB. We report that this ex situ XAS study will be used to support the analysis of an in situ XAS data collected on a PB containing supercapacitor to understand the mechanistic origin of pseudocapacitance in these devices.

42 ENGINEERING↗
DOE OSTI2024

Emergence of two distinct phase transitions in monolayer CoSe2 on graphene

Abstract Dimensional modifications play a crucial role in various applications, especially in the context of device miniaturization, giving rise to novel quantum phenomena. The many-body dynamics induced by dimensional modifications, including electron-electron, electron-phonon, electron-magnon and electron-plasmon coupling, are known to significantly affect the atomic and electronic properties of the materials. By reducing the dimensionality of orthorhombic CoSe 2 and forming heterostructure with bilayer graphene using molecular beam epitaxy, we unveil the emergence of two types of phase transitions through angle-resolved photoemission spectroscopy and scanning tunneling microscopy measurements. We disclose that the 2 × 1 superstructure is associated with charge density wave induced by Fermi surface nesting, characterized by a transition temperature of 340 K. Additionally, another phase transition at temperature of 160 K based on temperature dependent gap evolution are observed with renormalized electronic structure induced by electron-boson coupling. These discoveries of the electronic and atomic modifications, influenced by electron-electron and electron-boson interactions, underscore that many-body physics play significant roles in understanding low-dimensional properties of non-van der Waals Co-chalcogenides and related heterostructures. Graphical Abstract

36 MATERIALS SCIENCE↗