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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Open-source electrochemical cell for in situ X-ray absorption spectroscopy in transmission and fluorescence modes

X-ray spectroscopy is a valuable technique for the study of many materials systems. Characterizing reactions in situ and operando can reveal complex reaction kinetics, which is crucial to understanding active site composition and reaction mechanisms. In this project, the design, fabrication and testing of an open-source and easy-to-fabricate electrochemical cell for in situ electrochemistry compatible with X-ray absorption spectroscopy in both transmission and fluorescence modes are accomplished via windows with large opening angles on both the upstream and downstream sides of the cell. Using a hobbyist computer numerical control machine and free 3D CAD software, anyone can make a reliable electrochemical cell using this design. Onion-like carbon nanoparticles, with a 1:3 iron-to-cobalt ratio, were drop-coated onto carbon paper for testing in situ X-ray absorption spectroscopy. Cyclic voltammetry of the carbon paper showed the expected behavior, with no increased ohmic drop, even in sandwiched cells. Chronoamperometry was used to apply 0.4 V versus reversible hydrogen electrode, with and without 15 min of oxygen purging to ensure that the electrochemical cell does not provide any artefacts due to gas purging. The XANES and EXAFS spectra showed no differences with and without oxygen, as expected at 0.4 V, without any artefacts due to gas purging. The development of this open-source electrochemical cell design allows for improved collection of in situ X-ray absorption spectroscopy data and enables researchers to perform both transmission and fluorescence simultaneously. It additionally addresses key practical considerations including gas purging, reduced ionic resistance and leak prevention.

08 HYDROGEN↗
DOE OSTI2020

Electrochemical Characterization of Bromine Reduction to Tribromide in Individual Nitrobenzene-in-Water Emulsion Droplets

We report an electrochemical study of bromine reduction to tribromide in a single nitrobenzene (NB) droplet during a single collision event. The feasibility of this study is based on the favorable distribution of Br 2 in NB rather than in water, which was demonstrated by voltammetry at the NB/water interface. The NB-in-water emulsions containing the ionic liquids trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)amide (ILPA) as the supporting electrolyte and sodium dodecyl sulfate (SDS) as the surfactant were prepared by a high-power ultrasonication. Its single droplet as an attoliter reactor, colliding on a 25 μm Pt UME, was monitored by chronoamperometry. The spike-type current transients of Br 2 reduction can elucidate the size and size distribution of NB, and measure the diffusion in the droplet as analyzed by a bulk electrolysis model. The frequency of collisions can provide diffusion coefficient of the droplets to the UME. Moreover, the i-t decay behavior can be simulated, which fits well with the experimental one.

25 ENERGY STORAGE↗
DOE OSTI2020

In Situ Electrochemical Study of the Coexistence of Eu 3+ and Eu 2+ in Molten LiCl-KCl by Rotating Disc Electrode

In this study, a graphite rotating disc electrode was successfully designed and applied to conduct electrochemical measurements under flow conditions in molten LiCl-KCl at 773 K. The concentration and diffusion coefficients of Eu 3+ and Eu 2+ in molten salt were quantitatively measured with this electrode by applying in situ cyclic voltammetry and chronoamperometry techniques. The initial concentration ratio of Eu 3+ /Eu 2+ in LiCl-KCl-0.5 wt% EuCl 3 was calculated to be 2.37. The calculated diffusion coefficients of Eu 3+ and Eu 2+ in the salt were 9.31 ± 0.06 × 10 -5 cm 2 s -1 and 9.65 ± 0.6 × 10 -5 cm 2 s -1 , respectively. A decrease of the diffusion coefficient of Eu 3+ and Eu 2+ was observed at a higher concentration of EuCl 3 , which implies the enhanced Eu-Eu ion interaction. This electrode design is expected to be utilized for the concentration measurement of multivalent ions in a flowing molten salt.

Electrochemistry↗
DOE OSTI2021

Adsorption Processes during Electrochemical Atomic Layer Deposition of Gold

Electrochemical atomic layer deposition (e-ALD) technique offers a simple and effective "wet chemistry" approach enabling high-precision monolayer-by-monolayer deposition of metal films. The process of e-ALD of Au involves lead underpotential deposition (PbUPD) followed by its redox replacement by a Au monolayer. The time evolution of the deposit mass during "one-pot" Au e-ALD is known to exhibit a unique three-stage response that is presently not well understood. In this work, we probe this response using voltammetry, electrochemical quartz crystal microgravimetry (e-QCM), and chronoamperometry to unravel the underlying mechanistic events during Au e-ALD. Furthermore, the presence of adsorbed Au +3 -ligand complex(es) (Au-L) on the Au surface is established. In stage I of e-ALD, this Au-L adsorbed layer is reduced to Au while a Pb UPD adlayer is formed. In stage II, the Pb UPD adlayer undergoes spontaneous surface-limited redox replacement by nobler Au under open-circuit conditions. Finally, in stage III, re-adsorption of the Au-L occurs on the newly deposited Au. Quantitative analysis of the deposit mass transients obtained under a variety of conditions provides an estimate of the Au-L mass and its molecular weight.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Determination of Kinetic Properties of Ni(II) Ions in Molten LiF-NaF-KF via Voltammetry

Kinetic properties of Ni(II) in eutectic LiF-NaF-KF (FLiNaK) molten salt were determined at T = 748–823 K using cyclic voltammetry (CV), square wave voltammetry (SWV), and chronoamperometry (CA) measurements using a glassy C working electrode, Ni(II)/Ni reference electrode, and Ni counter electrode. Reduction of Ni(II) to Ni(s) was determined to be a single step, two-electron transfer process. Diffusivity values were calculated using the Berzins and Delahay equation and semi-integral electroanalysis from the CV measurements as well as using the Cottrell equation from the CA measurements. Diffusivity of Ni(II) in molten FLiNaK at T = 748–823 K was determined to be 3.27 × 10 –7 –3.04 × 10 –6 cm 2 s –1 with an activation energy of 62–104 kJ mol –1 . The estimated kinetic properties varied appreciably among methodologies possibly due to inherent assumptions in theory regarding reversibility and unit activity during Ni metal deposition on the working electrode.

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

Electrode Blocking Due to Redox Reactions in Aluminum Chloride-Sodium Iodide Molten Salts

Iodide redox reactions in molten NaI/AlCl 3 are shown to generate surface-blocking films, which may limit the useful cycling rates and energy densities of molten sodium batteries below 150 °C. An experimental investigation of electrode interfacial stability at 110 °C reveals the source of the reaction rate limitations. Electrochemical experiments in a 3-electrode configuration confirm an increase of resistance on the electrode surface after oxidation or reduction current is passed. Using chronopotentiometry, chronoamperometry, cyclic voltammetry, and electrochemical impedance spectroscopy, the film formation is shown to depend on the electrode material (W, Mo, Ta, or glassy carbon), as well as the Lewis acidity and molar ratio of I − /I 3 − in the molten salt electrolytes. These factors impact the amount of charge that can be passed at a given current density prior to developing excessive overpotential due to film formation that blocks the electrode surface. The results presented here guide the design and use of iodide-based molten salt electrolytes and electrode materials for grid scale battery applications.

25 ENERGY STORAGE↗
DOE OSTI2024

Study of Am electrodeposition from AmCl 3 -LiCl-KCl Molten Salt

In this work, the electrodeposition reaction of Am in AmCl 3 -LiCl-KCl molten salt was studied using voltammetry and chronoamperometry. Electrodeposition of Am was shown to proceed via a two – step reaction scheme, involving the one-electron transfer reduction of Am 3+ to Am 2+ , followed by the two-electron transfer reduction of intermediate Am 2+ to Am 0 . A low Coulombic efficiency of Am deposition was measured despite the Am deposition occurring within the thermodynamic stability window of the supporting LiCl-KCl electrolyte. We hypothesize that the low efficiency is due to out-diffusion of the intermediate Am 2+ species away from the electrode surface. Experimental observations provide evidence of a kinetically – limited electrodeposition reaction, which allows for the loss of intermediate Am 2+ via diffusion leading to Am deposition inefficiency.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Editors’ Choice—Rapid Deactivation Convolutes Electrochemical CO 2 Reduction Selectivity Measurements on Gold Rotating Ring Disk Electrodes

Voltammetric measurements of electrochemical CO 2 reduction reaction (CO 2 RR) selectivity on rotating ring disk electrodes (RRDE) are a rapid and sensitive method for quantifying an electrocatalyst’s selectivity, i.e. faradaic efficiency (FE). This method has been applied to polycrystalline Au electrocatalysts where a Au disk electrode catalyzes both the CO 2 RR and hydrogen evolution reaction while the concentric Au ring electrode selectively senses CO by oxidizing CO back to CO 2 . Such measurements enabled fundamental mechanistic studies but suffer from poor inter-laboratory reproducibility. This work identifies causes of variability in RRDE selectivity measurements by comparing protocols with different electrochemical methods, reagent purities, and glassware cleaning procedures. We observed FE CO decrease by 56% during 5 min chronoamperometry measurements, a phenomenon that is not readily apparent in voltammetric scans due to their dynamic nature. Electroplating of electrolyte impurities onto the disk and ring surfaces were identified as a major contributor to Au deactivation. Additionally, the oxygen reduction reaction may lead to higher disk currents in inadequately purged electrolytes, causing an apparent underestimation of FE CO at low overpotentials. Lastly, we propose operational bounds for CO 2 RR selectivity measurements on Au using the RRDE method and provide suggestions on steps for improving the accuracy of this technique.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Methods for Rotating Electrodes in High-Temperature Molten Salts

Abstract In this paper, we describe and validate a custom apparatus for performing high-speed (250-3,500 rpm) rotating electrode and dilatometer density experiments in molten salts. The reported details can aid in decreasing the difficulty and increasing the quality of such experiments. We discuss the design challenges and the solutions identified. We investigate methods for accurately measuring the solution resistance using electrochemical impedance spectroscopy, calculating the working electrode area using cyclic voltammetry, and measuring the mass transfer-limited current of rotating electrodes using a series of chronoamperometry pulses. We further demonstrate the efficacy of our methods in producing accurate results.

Fuller, Ranon (ORCID:0000000255400197)↗
DOE OSTI2025

On Stability and Electrochemical Performance of 316 Stainless Steel in Wastewater: Implications for Resource Recovery

Electrochemical nutrient recovery systems rely on stable electrode materials capable of operating in chemically complex wastewater environments. We investigated corrosion resistance and interfacial electrochemical behavior of 316 stainless steel (SS316) in a synthetic wastewater matrix representative of centrate streams, a key knowledge gap in electrochemical phosphorus recovery. A comprehensive suite of electrochemical techniques (chronoamperometry, cyclic voltammetry, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS)) and surface characterization methods (scanning electron microscopy, X-ray diffraction) were employed. Results revealed that wastewater containing typical ionic constituents (such as PO 4 3- , NH 4 + , and divalent cations) exhibited enhanced cathodic activity and the formation of a more stable, protective surface film on SS316 that mitigated chloride-induced corrosion. In contrast, SS316 in the NaCl solution showed significant susceptibility to passive layer breakdown and localized corrosion. Time-resolved EIS further confirmed improved interfacial stability and restricted charge transfer in WW over time, in stark contrast to the progressive passive layer degradation in NaCl. Surface analyses corroborated these findings, showing limited surface attack in WW compared to distinct localized corrosion features in NaCl. These findings indicate that competing ionic species in WW effectively mitigate chloride aggressiveness, enhance SS316 stability, and demonstrate improved electrode longevity and reliability for sustainable wastewater-based electrochemical phosphorus recovery applications.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Platinum and CeO 2-x Occlusion Electrodeposition at Unsupported Vulcan XC-72R for Methanol and Ethanol Oxidation Reactions in Alkaline Media

Abstract Platinum was electrodeposited in a slurry solution of CeO2 and Vulcan XC-72R to produce Pt/CeO2-x/Vulcan XC-72R catalysts by using the Rotating Disk Slurry Electrodeposition (RoDSE) Technique. The activity of the catalysts was measured towards methanol and ethanol oxidation reactions in alkaline conditions by cyclic voltammetry and chronoamperometry. The electrochemical results were compared to those obtained on commercial catalysts. Pt/CeO2-x/Vulcan XC-72R (with ~ 26 wt.% Pt) catalyst was the most active for both alcohol oxidation reactions when compared to commercial 40 wt.% and 20% /Vulcan XC-72R (ETEK) catalysts. The mass activity increases 2.0x and 2.4x for methanol and ethanol oxidation reactions when compare with 40 and 20 Pt wt. % commercial catalysts, respectively. The Pt/CeO2-x/Vulcan XC-72R catalysts contained Pt nanoparticles growth within the cerium oxide through an occlusion electrodeposition method. These effects were systematically investigated using X-ray Diffraction (XRD), High Resolution Transmission Electron Microscopy (HR-TEM), and X-ray Photoelectron Spectroscopy (XPS).

Suleiman Mahmoud, Amal↗
DOE OSTI2023

HunStat v4.10

Support for the following electrochemical techniques: · cyclic voltammogram (CV) · linear sweep voltammogram (LSV) · differential pulse voltammogram (DPV) · chronoamperometry (CA) Specific application: low-cost DIY potentiostat, demonstrating electrochemistry in the educational sector

Kertesz, Vilmos↗
DOE OSTI2021

Photoelectrochemically Self Improving Si/GaN Photocathode: Figure 1a Raw Data

10 hours chronoamperometry (CA) testing under 1 sun illumination and constant bias at -0.6 V vs RHE, the corresponding Faradaic efficiency reveals a self-improving nature of GaN, inset: CA testing on bare Si for 5 hours under 1 sun illumination and -0.6 V vs RHE, this bare Si photocathode rapidly drops down to < 0.05 mA/cm2 within an hour. Both CA testing performed in 0.5 M H2SO4 (pH=0.4).

photocathode↗
DOE OSTI2021

Photoelectrochemically Self Improving Si/GaN Photocathode: Figure 1c Raw Data

Intermittent chronoamperometry (CA) testing was performed on Si/GaN photocathode in hourly manner. The LSV scan at 0 hour, 1 hour CA, 2 hours CA, 3 hours CA, 4 hours CA, 6 hours CA, 8 hours CA and 10 hours CA were recorded to track the changes of the photoelectrochemica (PEC) performance of the photocathode. The scan range was set to be 0V vs open circuit voltage (Eoc) to -0.7V vs RHE. Test was performed under one sun illumination in 0.5M H2SO4 (pH=0.4).

photocathode↗
DOE OSTI2021

Photoelectrochemically Self Improving Si/GaN Photocathode: Figure 2d Raw Data

After 10 hrs of chronoamperometry (CA) photoconductive atomic force microscopy (PC-AFM) measurements were conducted on Si/GaN samples using a commercial AFM system (Bruker Dimension Icon). PeakForce TUNA mode was used to acquire the morphology and current simultaneously. A PtIr conductive probe with spring constant of 2.8 Nm-1 was used for the scanning. A white light source was used to illuminate the surface during the acquisition. Line scan extracting the topography and photocurrent from this 10 hour CA tested Si/GaN sample. The topography mapping is 2 × 2 µm2. No sample bias was applied and this photoconductive AFM measurement was performed under white light front illumination with an angle.

photocathode↗
DOE OSTI2021

Photoelectrochemically Self Improving Si/GaN Photocathode: Figure 3f Raw Data

XPS of Si/GaN photocathode after 10 hour chronoamperometry (CA) testing. Surface chemical composition and valence band structure of GaN were obtained by X-ray photoemission spectroscopy (XPS) on a Kratos Axis Ultra DLD system at a takeoff angle of 0° relative to the surface normal. An Al Kα source (hν = 1486.6 eV) was used to excite the core level electrons. Pass energy of 20 eV was used for the narrow scan of core levels and valence band spectra, and step size of 0.05 eV and 0.025 eV, respectively. The Spectral fitting was conducted using CasaXPS analysis software. The binding energy scales of all core levels were corrected to the N 1s of Ga – N bond at 397.8 eV. XPS O1s core level spectra from 10 hours CA tested Si/GaN sample, and deconvolution shows O - Ga bond, O - N - Ga bond and OH - H2O bond.

photocathode↗
DOE OSTI2021

Photoelectrochemically Self Improving Si/GaN Photocathode: Figure 3e Raw Data

XPS of Si/GaN photocathode after 4 hour chronoamperometry (CA) testing. Surface chemical composition and valence band structure of GaN were obtained by X-ray photoemission spectroscopy (XPS) on a Kratos Axis Ultra DLD system at a takeoff angle of 0° relative to the surface normal. An Al Kα source (hν = 1486.6 eV) was used to excite the core level electrons. Pass energy of 20 eV was used for the narrow scan of core levels and valence band spectra, and step size of 0.05 eV and 0.025 eV, respectively. The Spectral fitting was conducted using CasaXPS analysis software. The binding energy scales of all core levels were corrected to the N 1s of Ga – N bond at 397.8 eV. XPS O1s core level spectra from 4 hour CA tested Si/GaN sample, and deconvolution shows O - Ga bond, O - N - Ga bond and OH - H2O bond.

photocathode↗
DOE OSTI2022

Redox-Hopping-Based Charge Transport Mediated by Ru(II)-Polypyridyl Species Immobilized in a Mesoporous Metal-Organic Framework

Electronic charge transport through crystalline metal-organic frameworks (MOFs) can be accomplished by site-to-site electron (or hole) hopping, provided that redox-active sites, such as easily reducible or oxidizable MOF linkers, are present. If the framework itself is redox-inert, solvent-assisted ligand incorporation of redox-active moieties can serve to enable hopping-based charge transport. Here we have studied the redox hopping process within Ru-bpy@NU-1008, where Ru-bpy is a carboxylate-functionalized derivative, i . e ., a node-ligating derivative, of the well-known chromophore Ru(2,2′-bipyridine) 3 2+ , and NU-1008 is a redox-inert MOF featuring hierarchical porosity and csq topology. Chronoamperometry experiments with electrode-supported thin films of Ru-bpy@NU-1008 show that charge transport is feasible through portions of the MOF, with other portions being inaccessible. Possible confounding features are the undersized c- pores that cross-connect 1D mesoporous channels, as ingress and egress of charge-compensating anions is believed to accompany the net oxidation of Ru(II) to Ru(III) and the reduction of Ru(III) to Ru(II). Phenomenologically, transport through the electroactive portion of the films is diffusion-like, with the magnitude of the apparent diffusion coefficient being 6 × 10 −12 cm 2 /s.

Duan, Jiaxin↗