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At least 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Identifying Critical Electrode Metrics for Efficient, Selective CO 2 Electrochemical Conversion

Low-temperature electrochemical CO 2 reduction (CO 2 R) in zero-gap membrane electrode assembly (MEA) reactors presents a scalable route to fuels and carbon utilization. However, performance at industrially relevant current densities hinges on mesoscale catalyst layer integration, particularly at the ionomer|catalyst interface. Here, we demonstrate a generalizable in situ electrochemical impedance spectroscopy (EIS) method. We utilize this technique to decouple electrode-level parameters that are correlated to the overall MEA performance. By performing this ex situ EIS method on CO 2 -to-CO catalyst-coated membranes with systematically varied ionomer-to-catalyst (I:C) ratios, we reveal a pronounced dependence of performance, ion transport resistance, and catalyst utilization on the I:C ratio as well as the electrode conditioning. We demonstrate that an optimal I:C ratio exists at which ion transport resistance is minimized and Faradaic efficiency for CO production is maximized. Beyond the electrodes examined, here we compare ion transport resistance to MEA selectivity/Faradaic efficiency obtained in prior studies, revealing a clear correlation between the two. These results suggest that ion transport resistance within the catalyst layer may be a quantitative predictor of MEA performance which underscores the importance of mesoscale integration in achieving scalable CO 2 R technologies.

08 HYDROGEN↗
DOE OSTI2023

Boosting the Low-Temperature Performance of Graphite Anodes by Creating an Electrochemically Active Interface

Graphite is the major anode material used in commercial lithium-ion batteries (LIBs). However, the sluggish ion-transfer kinetics associated with graphite anodes significantly restrict the operation of LIBs over a wide temperature. This is primarily due to their low reversible capacity and the substantial overpotential exhibited under low-temperature conditions. To address this limitation, we demonstrate herein an approach that involves grafting an electrochemically active lithium benzenesulfonate layer onto a graphite surface through a typical reduction reaction of diazonium cations, followed by ion exchange process. This surface modification reduces the charge transfer resistance of graphite anodes, leading to an excellent reversible capacity of ~150 mAh g –1 at low-temperatures (-20 °C, 0.1C). Electrochemical impedance spectroscopy indicates that both desolvation of the lithium ions outside the graphite, and lithium diffusion within the solid electrolyte interphase and graphite lattice are two crucial rate-limiting steps during the Li (de)lithiation, with the latter dominating during the low-temperature operation. In conclusion, these findings demonstrate a facile method for enhancing the low-temperature performance of graphite through surface modification and provide valuable insights into fundamental understandings that can guide the future design of better -low-temperature graphite anodes.

25 ENERGY STORAGE↗
DOE OSTI2025

Old Woman Creek Wetland Sediment and Electrochemical Sensor Microbial Community, 2023

We are developing a technique to monitor microbiological activities referred to as zero resistance ammetry, which entails the deployment of graphite electrodes in sediments. Measurement of current between electrodes of contrasting redox regimes and/or predominant terminal electron accepting processes can be used as an indicator of the extents of microbiological activity. We deployed an electrode array at depths of 2 mm, 4 mm, 76 mm, 78 mm, 152 mm, 154 mm, 227 mm, and 229 mm below the wetland sediment water interface in the Old Woman Creek National Estuarine Research Center, Huron, OH, USA (Lat. = 41.380833, Long. = -82.508889). A core was collected from adjacent sediment and subsamples were collected from depth intervals of 0 – 25 mm, 25 – 127 mm, 127 – 128 mm, and below 178 mm. To determine if the microbial communities attached to the electrodes were reflective of the adjacent sediment-associated microbial community, we conducted a 16S rRNA gene-based (V4 region) survey of these respective materials. This data package contains the results of these surveys, including metadata on the depths from which samples were collected (samples.csv), DNA extraction and sequencing information (OWC_DEPTH_AMPLICON_SEQUENCING_METADATA), sequence processing information (OWC_DEPTH_BIOINFORMATIC_METADATA.csv), an operational taxonomic unit (OTU) table (OWC_DEPTH_97OTUS_TABLE.csv), and nucleotide sequences of OTUs (OWC_DEPTH_97OTUS_SEQS.fasta). All files can be opened using a text-editing application. The fasta file is compatible with bioinformatics applications.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Deposition pressure dependent structural and optoelectronic properties of ex-situ boron-doped poly-Si/SiO x passivating contacts based on sputtered silicon

Among common methods to form polycrystalline silicon (poly-Si) films for passivating-contact solar cells, physical vapor deposition, in particular sputtering, is the safest one as it does not require any toxic gaseous precursors. One of the critical parameters to control the properties of sputtered silicon films is their deposition pressure. In this work, structural and optoelectronic characteristics of ex-situ boron-doped poly-Si/SiO x passivating contacts, formed from sputtered intrinsic amorphous silicon (a-Si) deposited at different pressures on top of SiO x /c-Si substrates and subjected to a high-temperature boron diffusion step, are investigated. The deposition rate and density of the as-deposited a-Si films increase with reducing pressure. Low-temperature photoluminescence spectra captured from the as-deposited samples at different pressures do not show typical emissions from hydrogenated a-Si. Meanwhile, their Fourier-transform infrared absorption spectra all show Si–H stretching modes, indicating that hydrogen had been initially incorporated into the chemical SiO x layers and eventually hydrogenated the a-Si/SiO x interfaces during the sputtering process. After the high-temperature boron-diffusion step, all hydrogen-related peaks disappear. Lower pressure films (1.5 and 2.5 mTorr) show more consistent improved performance after hydrogen treatments, compared to higher pressure films (4 and 5 mTorr). Overall, the resultant passivating contacts at 2.5 mTorr achieve a low single-side recombination current density Jo of ~9 fA/cm 2 , whereas their contact resistivity is still low at 15 mO cm 2 .

14 SOLAR ENERGY↗
DOE OSTI2020

Development and Characterization of 3D-Printed Cementitious Sytems for Innovative Nuclear Systems

The Transformational Challenge Reactor (TCR) is being developed to demonstrate a revolutionary approach to deploying new nuclear power systems by building and operating an additively manufactured microreactor. This initiative provides a unique opportunity to investigate the possibility of taking advantage of the recent development of the 3D-printed concrete system using the Sky Big Area Additive Manufacturing (SkyBAAM) printer at the Manufacturing Demonstration Facility (MDF) at Oak Ridge National Laboratory. Two pathways have been pursued in parallel since the end of the second quarter of FY19: 1. Development of methods to characterize the performance of additive manufacturing concrete using traditional Portland-cement based solution, and 2. Investigation of the opportunity to develop innovation of printable materials with higher irradiation-resistance performance using nontraditional concrete solutions in favor of carbonated cementitious materials (CCMs). This report describes the results achieved to date for both pathways. The main results are listed below: 1. A test protocol has been established to characterize the fracture properties of 3D-printed concrete; this protocol will be used to assess the performance of printed traditional and nontraditional cementitious materials, with a focus on performance of the interfaces inherent to the additive manufacturing process. 2. A state-of-the-art review of the mechanisms, fabrication method, and performance of CCMs was conducted. CCMs appear to be a viable, highly innovative, more performant alternative to Portland-based cementitious solution for the erection of biological shield pending some materials development.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2024

Al-Ce Alloy-Based Compact Heat Exchanger for Refrigerant Charge Reduction and Unprecedented Durability (CRADA NFE-21-08888 Final Report)

Oak Ridge National Laboratory and Eck Industries produced and characterized durable and corrosion resistant Al-Ce-Mg alloy-based heat exchanger. Eck Industries successfully casted Al-Ce-Mg heat exchanger. ORNL characterized reaction bonding between Al-2Ce-6Mg alloy and stainless-steel tube in a heat exchanger header. Metallurgical bonds were achieved between stainless steel tubes and Al-Ce-Mg alloy cast headers. ORNL performed corrosion testing on Al-Ce-Mg alloy/stainless steel tube reactive bond interface. In most cases no significant changes to the reactive bond morphology or compositional distribution were observed in the samples after exposure to acid for 267h acid.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Al-Ce Alloy-Based Compact Heat Exchanger for Refrigerant Charge Reduction and Unprecedented Durability

• Oak Ridge National Laboratory and Eck Industries produced and characterized durable and corrosion resistant Al-Ce-Mg alloy-based heat exchanger. • Eck Industries successfully casted Al-Ce-Mg heat exchanger. • ORNL characterized reaction bonding between Al-2Ce-6Mg alloy and stainless-steel tube in a heat exchanger header. • Metallurgical bonds were achieved between stainless steel tubes and Al-Ce-Mg alloy cast headers. • ORNL performed corrosion testing on Al-Ce-Mg alloy/stainless steel tube reactive bond interface. • In most cases no significant changes to the reactive bond morphology or compositional distribution were observed in the samples after exposure to acid for 267h acid.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Electroanalytical Measurement of Interphase Formation at a Li Metal–Solid Electrolyte Interface

The interphase between Li metal and solid electrolytes dictates performance in Li metal batteries. For the solid electrolyte Lipon, in this study we electroanalytically measure a capacity loss of 1.03 ± 0.16 μAh/cm 2 when Lipon first contacts Li metal. Assuming this capacity is all lost to interphase formation, this corresponds to a maximum Li consumption of 5.0 ± 0.8 nm to form an interphase ~4.7 nm thick. From dynamic electrochemical impedance spectroscopy (dEIS) during Li plating, we determine that nonlinear chaotic spectra demark this interphase formation and that this occurs immediately upon initiation of Li plating. dEIS also reveals interfacial resistance during both plating and stripping that decreases as the amount of plated Li increases.

25 ENERGY STORAGE↗
DOE OSTI2024

Detection of a Cobalt-Containing Interphase at the Li 6 PS 5 Cl-NMC111 Interface by In Situ μ XANES and EIS

Sulfide electrolyte all-solid-state lithium batteries (ASLBs) with uncoated Li-Ni x Mn y Co 1–x–y O 2 (NMC) cathodes suffer from a large capacity loss during initial cycling and an increase in cell impedance. Decomposition reactions are known to occur at the Li 6 PS 5 Cl-NMC111 interface due to incompatibility between the two materials. If a stabilizing coating is applied to the NMC, it delivers full capacity during initial charge. However, the loss in capacity during discharge still occurs. The interface was studied by μ XANES and through EIS analysis. A chemically-formed interphase was detected by μ XANES, evident from reduction of Co at an uncoated NMC particle surface. This interphase was produced by decomposition at rest. To study the effect of the interphase on electrochemically active surface area, piecewise in situ EIS was performed and the data was modeled using a transmission line model (TLM). The charge transfer resistance R CT was used to estimate the volume specific active surface area (a act ). The median value for a act was 296 cm –1 , a factor of 7.5 lower than the theoretical value of 2216 cm –1 . This provided evidence of a lower electrochemically active surface area in the ASLB.

36 MATERIALS SCIENCE↗
DOE OSTI2024

High-current, high-voltage AlN Schottky barrier diodes

AlN Schottky barrier diodes with low ideality factor (<1.2), low differential ON-resistance (<0.6 mΩ cm 2 ), high current density (>5 kA cm −2 ), and high breakdown voltage (680 V) are reported. The device structure consisted of a two-layer, quasi-vertical design with a lightly doped AlN drift layer and a highly doped Al 0.75 Ga 0.25 N ohmic contact layer grown on AlN substrates. A combination of simulation, current–voltage measurements, and impedance spectroscopy analysis revealed that the AlN/AlGaN interface introduces a parasitic electron barrier due to the conduction band offset between the two materials. This barrier was found to limit the forward current in fabricated diodes. Further, we show that introducing a compositionally-graded layer between the AlN and the AlGaN reduces the interfacial barrier and increases the forward current density of fabricated diodes by a factor of 10 4 .

Quiñones, C. E. (ORCID:0000000192703747)↗
DOE OSTI2021

Utilizing the unique charge extraction properties of antimony tin oxide nanoparticles for efficient and stable organic photovoltaics

Simultaneously enhancing device performance and longevity, as well as balancing the requirements on cost, scalability, and simplification of processing, is the goal of interface engineering of organic solar cells (OSCs). In our work, we strategically introduce antimony (Sb 3+ ) cations into an efficient and generic n-type SnO 2 nanoparticles (NPs) host during the scalable flame spray pyrolysis synthesis. Accordingly, a significant switch of conduction property from an n-type character to a p-type character is observed, with a corresponding shift in the work function (WF) from 4.01 ± 0.02 eV for pristine SnO 2 NPs to 5.28 ± 0.02 eV for SnO 2 NPs with 20 mol. % Sb content (ATO). Both pristine SnO 2 and ATO NPs with fine-tuned optoelectronic properties exhibit remarkable charge carrier extraction properties, excellent UV resistance and photo-stability being compatible with various state-of-the-art OSCs systems. The reliable and scalable pristine SnO 2 and ATO NPs processed by doctor-blading in air demand no complex post-treatment. Our work offers a simple but unique approach to accelerate the development of advanced interfacial materials, which could circumvent the major existing interfacial problems in solution-processed OSCs.

14 SOLAR ENERGY↗
DOE OSTI2026

Heterogeneous Corrosion Pathways in Pt–Ni Nanododecahedra Revealed by In Situ Liquid Cell TEM

Unraveling nanoscale corrosion pathways is essential for understanding materials degradation mechanisms and designing corrosion-resistant metal alloys. Here, in this study, we directly visualize the corrosion of Pt–Ni nanododecahedra in 0.1 M HCl using liquid cell TEM. Each nanoparticle features a Ni-rich core and a Pt-rich frame. Our observation reveals that corrosion proceeds in two distinct stages: first the Ni-rich core dissolves without forming porosity, yielding small Pt nanocrystals and transient NiCl 2 ·6H 2 O at the retreating interfaces; then the Pt-rich frame fragments into ∼5 nm Pt 3 Ni nanocrystals that subsequently dissolve uniformly, accompanied by fleeting Pt chlorides. A percolation-based theory explains the observed behaviors: The core’s ∼8% Pt lies below the Pt connectivity threshold, preventing Pt scaffold formation, whereas the frame’s 48% Ni exceeds the Ni percolation threshold and collapses. Ordered Pt 3 Ni suppresses Ni percolation, thereby enforcing uniform dissolution. These findings reveal how composition and structural ordering govern heterogeneous corrosion in Pt–Ni architectured nanoparticles.

Liquid phase TEM↗
DOE OSTI2021

Operating Stresses and Their Effects on Degradation of LSM-Based SOFC Cathodes

The performance of solid oxides fuel cells (SOFCs) with four different Mn excess of lanthanum strontium manganite (LSM) -based cathodes were examined under different temperatures (1,000 °C, 900 °C), current densities (0, 380, and 760 mA cm -2 ), and cathode atmospheres (p O 2 )=0.1,0.15,0.21) for durations ranging from 58 to 1,008 h. Each yttria-stabilized zirconia (YSZ) electrolyte-supported “button” cell had a porous Ni/YSZ composite anode and a porous LSM/YSZ composite cathode. The cells’ output voltage versus time were recorded and electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV) measurements were performed every 24 hours. The total area specific resistance (ASR) was calculated from these measurements. The values of ASR from both EIS and LSV were comparable between each other but lower than that from durability test. Distribution of relaxation times (DRT) analysis was performed to investigate the electrochemical processes and their corresponding relaxation frequencies as well as their attributions to the total ASR. The series resistance and parallel resistance that obtained from the equivalent circuit fit of the Nyquist plot were higher at low temperature and low p O 2 regardless of LSM compositions. The area of the peaks derived from DRT analysis increased with time during individual tests. The microstructures of the tested cells were examined using scanning electron microscopy and energy-dispersive x-ray spectroscopy (SEM/EDS). Manganese oxide particles were observed near the cathode-electrolyte interface after prolonged (1,008 h) testing in air of a cell with LSM of 11% manganese excess, and after a short test (58 h) under low oxygen (p O 2 = 0.10) in a cell with LSM of 5% manganese excess. However, the role of MnOx in cell degradation is still unknown.

08 HYDROGEN↗
DOE OSTI2025

Development of a Robust Reference Electrode in Aggressive Chemical and Radiation Environments in the Hanford Waste Tanks

The Hanford site stores more than 200 million liters of radioactive and chemically hazardous wastes from the production of weapons materials. The wastes are stored in 177 underground carbon-steel storage tanks, separated between 149 single shell tanks (SSTs) and 28 double shell tanks (DSTs). The DSTs provide critical retrieval and interim storage before the waste is vitrified in the Waste Treatment and Isolation Plant (WTP). The tanks will need to remain in-service far beyond the initial 40-year design life, and effective corrosion control practices must remain in force to extend the tanks’ lifespans. This effort includes direct measurements of corrosion rate (e.g., ultrasonic measurements and corrosion coupons) and electrochemical processes (e.g., linear polarization measurements and open circuit potential measurements). The Hanford site began monitoring the corrosion potential in select DSTs in 2008. Of the 45 reference electrodes that have been installed, 29 have failed and 6 others provided unreliable results. DOE-EM is supporting a 3-year program to develop a chemical and radiation resistant reference electrode for application in the Hanford tanks. The first year of the program focused on understanding the failure mechanism for the reference electrodes and identification of candidate construction materials that would mitigate degradation of the electrodes in the waste environment. During the second year of the program, the objectives were to: 1) test candidate materials under simulated waste conditions, 2) design components that will extend the service life of the electrode, 3) fabricate materials for prototype reference electrodes, and 4) assemble prototype reference electrodes for accelerated testing. The reference electrode is constructed of four principal parts: 1) junction, 2) casing, 3) inner chamber backfill materials, and 4) the sensing wire. Principally, improvements of the junction, casing, and inner chamber backfill materials are being pursued. The junction material at the interface between the waste and the inner chamber of the reference electrode was identified as a critical component in the failure of the reference electrodes. Nine candidate replacement junction materials were tested under simulated waste conditions to evaluate permeation rate. These materials included a variety of polymeric and ceramic materials, some of which were 3-D printed. Thus far, porous polyvinylidene fluoride materials have performed satisfactorily and are being considered for prototype development. The commercial electrode casing materials in general have performed well. Additionally, 3-D printing of chemically and mechanically stable materials is being investigated as a means for further improvement in fabrication consistency. SRNL has also investigated altering the reference electrode design to extend the service life. The new design of the interior of the reference electrode casing creates a longer, more tortuous path between the junction material and the electrode sensing wire. A finite element model was used to optimize the design without adversely impacting the circuit resistance of the electrode during the measurements, thus preserving the measurement accuracy while enhancing the service life. The inner chamber back fill materials are also critical to the performance of the reference electrode. Materials that are resistant to intruding tank waste and provide a conductive path to the sensing wire were investigated. Gel and powder materials that are interspersed with a conductive chloride bearing material were tested for their influence on diffusion and electrode resistance. All the investigated materials and components will be assembled, with collaboration from commercial vendors, to fabricate the initial prototypes. Accelerated testing of the prototypes will be initiated in Year 2 of the program and will be completed in Year 3. A recommendation on the materials of construction and the design of the new robust reference electrode will be presented to the Hanford tank farm facility.

Sykes, Kiana [Savannah River National Laboratory (↗
DOE OSTI2021

Tunable topological Hall effects in noncollinear antiferromagnet Mn 3 Sn/Pt bilayers

Noncollinear antiferromagnet Mn3Sn has attracted wide interest as it is a candidate for Weyl semimetal. Here, we report the observation of topological Hall like signals in Mn3Sn/Pt bilayers grown on Al 2 O 3 (0001). X-ray diffraction and scanning transmission electron microscopy results confirm the high epitaxial quality of the c-axis-oriented Mn3Sn films. The detected topological Hall resistivity shows a broad temperature range from 210 to 365 K by tuning the thickness of Mn3Sn from 3 to 15 nm. Compared with previously reported topological Hall effects in Mn3Sn at temperatures below 50 K, the observed high-temperature topological Hall signal is likely due to the stabilization of topological spin textures enabled by the strong spin–orbit coupling of the Pt overlayer and the Dzyaloshinskii–Moriya interaction at the Mn3Sn/Pt interface.

36 MATERIALS SCIENCE↗
DOE OSTI2020

In-situ and in-operando analysis of voltage losses using sense wires for proton exchange membrane water electrolyzers

Proton exchange membrane water electrolyzer development requires understanding processes at the materials and interface levels to reach the required performance and lifetime targets for increasing market penetration. To achieve the required progress, it is critical to develop advanced in-situ diagnostics that allow observation of the changes that come with the reduction of catalyst loading combined with long-term intermittent operation. This work presents an internal voltage sensing method that enables observing internal voltage drops in an operating electrolyzer cell. It allows the total cell resistance to be separated into anode, CCM, and cathode resistance. The method is demonstrated by operating cells with different anode porous transport layers (PTLs). The changing properties of the PTLs result in significant variations of the resistances. Enhancing the PTL properties with a protective coating reduces the anode resistance significantly. In addition to these observations, the method enables a real-time monitoring of resistance related values that impact performance in water electrolyzers. Long-term experiments with the method allow us to gain insights into processes that occur during operation such as conditioning or degradation. The internal voltage sensing method presented in this study is a novel technique for diagnosing, analyzing, and optimizing water electrolyzers and other energy conversion devices.

42 ENGINEERING↗
DOE OSTI2020

Comparison of passivation properties of plasma-assisted ALD and APCVD deposited Al 2 O 3 with SiN x capping

In this paper, we report on the direct comparison of Al 2 O 3 films deposited by plasma-assisted atomic layer deposition (ALD) and atmospheric pressure chemical vapor deposition (APCVD) techniques on the passivation properties of both bare and boron diffused Si surfaces. It is found that ALD and APCVD deposited Al 2 O 3 layers with SiN x capping have very similar chemical composition, hydrogen concentration at the Al 2 O 3 /Si interface, and interface defect density (D it ), but the ALD film has slightly higher negative fixed charge (Q f ) after a high temperature (~750 °C) contact firing cycle typically used for solar cell fabrication. Both films showed excellent surface recombination velocities of <5 cm/s on planar and textured un-diffused Si wafers, but the ALD films gave 1 to 8 fA/cm 2 lower emitter saturation current densities (J 0e ) on implanted boron emitters with sheet resistance in the range of 90–180 Ω/. This is attributed to the observed slightly higher negative charge-induced field-effect passivation in the ALD films. However, SiN x /Al 2 O 3 /p + /n/n + passivated emitter rear totally diffused (PERT) cell structures fabricated with 110 and 150 Ω/ emitter in this study showed no appreciable difference in cell efficiency. Device analysis and simulations showed that even for >23% high-performance solar cells design, with very low bulk and rear contact recombination, the observed small difference in J 0e has negligible effect on cell efficiency. Furthermore, APCVD Al 2 O 3 passivation of B emitter can produce comparable efficiencies to their counterpart ALD Al 2 O 3 passivated n-type Si solar cells.

14 SOLAR ENERGY↗