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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

One step electrochemical synthesis of bimetallic PdAu supported on nafion–graphene ribbon film for ethanol electrooxidation

Highlights: • Electrochemical deposition of bimetallic PdAu NPs. • Highly loaded PdAu NPs are obtained. • Nafion–graphene supported PdAu NPs shows good activity for ethanol electrooxidation. - Abstract: A nafion–graphene ribbon (Nf–GR) supported bimetallic PdAu nanoparticles (PdAu/Nf–GR) catalyst was prepared by electrochemical codeposition of Pd and Au at constant potential. The prepared catalyst was characterized by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), transmission electron microscopy (TEM) and X-ray diffraction analysis (XRD). The average particle size of PdAu nanoparticles (NPs) determined from XRD was 3.5 nm. The electrocatalytic activity of the PdAu/Nf–GR catalyst was examined by cyclic voltametry. It was observed that the as prepared catalyst showed efficient activity and good stability for ethanol electrooxidation in alkaline medium.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2016

One-pot solvothermal synthesis of ordered intermetallic Pt{sub 2}In{sub 3} as stable and efficient electrocatalyst towards direct alcohol fuel cell application

Ordered intermetallic Pt{sub 2}In{sub 3} nanoparticles have been synthesized by superhydride reduction of K{sub 2}PtCl{sub 4} and InCl{sub 3}.xH{sub 2}O precursors using facile, one-pot solvothermal method. We report surfactant free solvothermal synthesis of a novel ordered Pt{sub 2}In{sub 3} intermetallic nanoparticles for the first time. The structure and morphology of the catalyst has been confirmed by powder X-ray diffraction, transmission electron microscopy, field emission scanning electron microscopy, energy-dispersive spectrometry and X-ray photoelectron spectroscopy. The electrocatalytic properties of the catalysts have been investigated by cyclic voltammetry and chronoamperometry. The as prepared Pt{sub 2}In{sub 3} catalyst exhibit far superior electrocatalytic activity and stability towards alcohol oxidation over commercial Pt/C. The specific activity of as synthesized catalyst was found to be ~3.2 and ~2.3 times higher than commercial Pt/C for methanol and ethanol oxidation, respectively. This improved activity and durability of the Pt{sub 2}In{sub 3} nanoparticles can make the catalyst an ideal catalyst candidate for direct alcohol fuel cell. - Graphical abstract: The ordered structure of Pt{sub 2}In{sub 3} nanoparticles synthesized by solvothermal method has confirmed through XRD and TEM. Cyclic voltametry and chronoamperometry showed improved catalytic activity and stability compared to commercial Pt/C. - Highlights: • Ordered Pt{sub 2}In{sub 3} nanoparticles were synthesized by solvothermal method. • Electrooxidation of alcohols on Pt{sub 2}In{sub 3} catalyst was investigated in acidic medium. • Pt{sub 2}In{sub 3} catalyst has superior catalytic activity compared to commercial Pt/C. • Pt{sub 2}In{sub 3} catalyst exhibited much higher stability than commercial Pt/C.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1974

An electrochemical study of a liquid crystal used in information displays

The operational lifetime of liquid crystal displays were investigated. Electrochemical reaction at the electrodes of the display can cause failure after 2000 to 3000 hours of operation. Studies using cyclic voltametry of electrochemical reactions of N (p-methoxybenzilidene p-butylaniline (MBBA), a nematic liquid crystal were made. These studies indicate the presence of a reversible reduction of MBBA at the cathode, and that the reduction product undergoes a further reaction leading to products which are not reversibly oxidized. It is concluded that the degradation of the liquid crystal in displays can be reduced with a suitable frequency of alternating voltage.

Oglesby, D. M.↗
NASA NTRS1982

An electrochemical study of Ni/2+/, Co/2+/, and Zn/2+/ ions in melts of composition CaMgSi2O6

Results are reported for a study of the behavior of Ni(2+), Co(2+), and Zn(2+) in molten diopside, determined by cyclic voltametry, as a first step in adapting electrochemical methods for use in experimental geochemistry. The techniques used are described, the theory is briefly discussed, and it is demonstrated that Ni(2+), Co(2+), and Zn(2+) can be reduced, then reoxidized in an uncomplicated case of reversible charge transfer at the Pt electrode. This implies that the neutral metal atoms remain undissolved in the melt. The kinetics of the reduction process, the effects of concentration, the standard reduction potentials, and the diffusion coefficients are discussed in detail. The observations are consistent with the mechanism of Ni(2+) diffusion by transport from site to site. As the proportion of SiO2 in the melt increases, a higher activation energy is required for Ni(2+) to move, and the rate of diffusion is lowered.

Semkow, K. W.↗
DOE OSTI2018

A Voltammetric Sensor Based on MgFe2O4 Decorated on Reduced Graphene Oxide-modified Electrode for Sensitive and Simultaneous Determination of Catechol and Hydroquinone

In this work facile one step synthesis of magnesium ferrite (MgFe2O4) nanoparticles decorated on reduced graphene oxide (MgFe@RGO) using a microwave assisted hydrothermal procedure is reported. The synthesized material was characterized with help of several techniques and applied for the modification of glassy carbon electrode. Such prepared electrode was utilized for successive simultaneous detection of structurally similar compounds, 1,2- and 1,4-dihydroxibenzenes (catechol (CC) and hydroquinone (HQ)), using differential pulse voltammetry technique. It was found that oxidation current increases linearly with the concentrations of both investigated compounds. Detection limits for both species are ≤0.31 μM. The best analytical response in the presence of both CC and HQ, taking into account peak shape and peak current, was obtained at pH 5.6 utilizing acetate buffer solution. The often-presented species in the surface waters as well as gallic acid and caffeine do not interfere with determination of CC and HQ, while ascorbic acid shows high interference. The method is successfully applied for detection of catechol and hydroquinone in real samples analyses. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Carbazole Substituted BODIPYs: Synthesis, Computational, Electrochemical and DSSC Studies

Carbazole and p-anisyl substituted BODIPY dyes with a cyanoacetic acid anchoring group have been prepared and their spectral, electrochemical properties and photosensitizing potential in DSSC have been evaluated. X-ray structure of N-phenylcarbazole substituted BODIPY revealed lower torsion angle between BODIPY plane and carbazole plane, suggesting increased communication between the two units. DFT studies indicated effective electronic interactions between the BODIPY unit and carbazole substituents. The N-butylcarbazole and N-phenylcarbazole substituted BODIPYs showed anodic shifts in their reduction potentials, indicating facile reduction process. The predicted HOMO–LUMO gaps are in agreement with the electrochemical result and the lower band gap was observed for the carbazole substituted BODIPYs.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Spectral, Electrochemical and Computational Investigations of Binding of n-(4-Hydroxyphenyl)-imidazole with p-Sulfonatocalix[4]arene

The interaction of n-(4-hydroxyphenyl)-imidazole with p-sulfonatocalix[4]arene is studied using fluorescence technique. The quenching of fluorescence intensity explains the efficiency of binding via binding constant and quenching constant. The excited state lifetime of n-(4-hydroxyphenyl)-imidazole is decreased upon interaction with p-sulfonatocalix[4]arene. The cyclic voltametric studies emphasized the interaction of n-(4-hydroxyphenyl)-imidazole with p-sulfonatocalix[4]arene. Quantum chemical calculations are carried out to study the interactions as well as charge transfer between the host and the guest upon complexation. The simulations revealed that the n-(4-hydroxyphenyl)-imidazole interacts with p-sulfonatocalix[4]arene with horizontal orientation with in the p-sulfonatocalix[4]arene cavity.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2019

Electrochemical Investigations of Magnetic Co{sub 3}O{sub 4} Nanoparticles as an Active Electrode for Supercapacitor Applications

This attempt reports on cobalt oxide (Co{sub 3}O{sub 4}) nanoparticles (NPs) prepared through the traditional chemical reflux method to examine the behavior of supercapacitor performance. The synthesized NPs were characterized using several analytical tools such as ultraviolet-visible spectroscopy (UV), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) pattern, and scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDX). Moreover, the electrochemical performance was analyzed using galvanostatic charge and discharge studies (GCD), cyclic voltammetry (CV) studies as well as electrochemical impedance spectroscopy (EIS). The cubical phase of Co{sub 3}O{sub 4} was identified from the XRD pattern and also the average crystalline size was measured by Scherrer’s equation. FTIR confirmed the functional group of Co{sub 3}O{sub 4} NPs. SEM images revealed the hexagonal-shaped nanoflakes-like morphology of the sample. From the elemental analysis, the formation of pure Co{sub 3}O{sub 4} NPs by means of high purity and composition ratio of cobalt with oxygen was found. Vibrating sample magnetometer (VSM) plot scrutinized the magnetic performance of Co{sub 3}O{sub 4} NPs{sub .} The Co{sub 3}O{sub 4} NPs modified electrode has delivered maximum specific capacitance as 1413 Fg{sup −1} at a current density of 1 Ag{sup −1} which maintains tremendous cycling stability within the retention ratio of 98.4% after 1000 cycles. .

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Voltammetric determination of vitamin B{sub 6} (pyridoxine) at a graphite screen-printed electrode modified with graphene oxide/Fe{sub 3}O{sub 4}@SiO{sub 2} nanocomposite

The preparation and study of electrochemical properties of a graphite screen-printed electrode (SPE) modified with the GO/Fe{sub 3}O{sub 4}@SiO{sub 2} (GO is graphene oxide) nanocomposites are described. The morphologies of the GO/Fe{sub 3}O{sub 4}@SiO{sub 2} nanocomposites were examined by scanning electron microscopy. The electrochemical oxidation of vitamin B{sub 6} (pyridoxine) on SPE modified with the GO/Fe{sub 3}O{sub 4}@SiO{sub 2} nanocomposite was investigated by cyclic voltammetry, differential pulse voltammetry, and chronoamperometry. Under optimum conditions (pH 7.0), the vitamin B{sub 6} oxidation at the surface of the modified SPE occurs at a potential about 190 mV less positive than that at the unmodified SPE. A linear voltammetric response for vitamin B{sub 6} was obtained in the concentration range 1.0•10 {sup 6}—9.0•10 {sup 4} mol L{sup –1} with a detection limit of 5.2•10 {sup 7} mol L{sup –1} using differential pulse voltammetry. The developed sensor was also successfully applied for determination of trace level of vitamin B{sub 6} in both the standard vitamin B{sub 6} sample and biological samples (urine).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Oxidative transformation of N-substituted 3-aminopyrazoles to azopyrazoles using electrogenerated bromine as a mediator

The one-pot process of anodic transformation of N-alkyl-3-aminopyrazoles into azopyrazoles under conditions of membraneless electrolysis in an aqueous solution of NaBr was studied for the first time. It was found that under these conditions the aminopyrazoles, which do not have a substituent at position 4, transform into the corresponding 4,4´-dibromoazopyrazoles. The corresponding yield was in the interval of 28—80%, depending on the structure of the products. The transformation of 4-substituted aminopyrazoles resulted in the formation of azopyrazoles in the yields lying within 62—86% when this process was implemented under conditions with the anodically generated Br{sub 2} acting as a mediator. A convenient method of anodic synthesis of azopyrazoles in an aqueous medium without the use of additives of chemical oxidants was proposed. The process is environmentally sound and is characterized by a high atom efficiency (>85%).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Synthesis and characterization of new N-{4,6-bis[2-(het)arylvinyl]pyrimidin-2-yl}-substituted polycyclic aromatic imides

Two series of new N-{4,6-bis[2-(het)arylvinyl]pyrimidin-2-yl}-substituted aromatic polycyclic imides were synthesized. The synthesized chromophores were characterized by UV and fluorescence spectroscopy, cyclic voltammetry, and quantum chemical density functional theory calculations. A change in the nature of aryl (hetaryl) moieties was found to cause changes in the optical properties of both solutions of these compounds and thin films prepared from these compounds. The replacement of the phthalimide moiety by the 1,8-naphthalimide one has led to a significant increase in the lowest unoccupied molecular orbital energy.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Yttria-Stabilized Zirconia Aided Electrochemical Investigation on Ferric Ions in Mixed Molten Calcium and Sodium Chlorides

Electrolytic reduction of dissolved iron oxide to metal iron in molten salts with an inert anode is an alternative short route for steelmaking without CO{sub 2} emissions. A novel and simple integrated yttria-stabilized zirconia (YSZ) cell was constructed from a YSZ tube with a closed end. The YSZ tube played multiple functions, including the container for the molten salts, the solid electrolyte membrane in the O{sup 2−}|YSZ|Pt|O{sub 2} (air) reference electrode (RE), and the solid electrolyte membrane between the working and counter electrodes (WE and CE). Electrochemical behavior of ferric ions (Fe{sup 3+}) that were formed by dissolution of 0.5 wt pct Fe{sub 2}O{sub 3} in the molten CaCl{sub 2}-NaCl eutectic mixture was investigated on a Pt WE at 1273 K by various electrochemical techniques including cyclic voltammetry, linear scan voltammetry, square wave voltammetry, chronopotentiometry, chronoamperometry, and potentiostatic electrolysis. Analysis of the mechanism of electrode reactions was further assisted by scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. Some electrochemical parameters were obtained, including the number of exchanged electrons and the diffusion coefficient of ferric ions in the mixed molten salts. The results from various electrochemical techniques are in good agreement with each other, and show that the electrochemical reduction of Fe{sup 3+} to Fe in the molten salt mixture could be a single three-electron transfer step and diffusion-controlled reaction that was also possibly reversible. This work may form the foundation for extraction of iron and alloys from molten salts and also provide a stable O{sup 2−}|YSZ|Pt|O{sub 2} (air) RE with wide applicability for investigation on electrochemical properties of other electroactive metal oxides in molten salts.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Direct Observation of Pure Cu and Cu-Ag Anode Passivation in H{sub 2}SO{sub 4}-CuSO{sub 4} Aqueous Solution by Channel Flow Double Electrode and Optical Microscopy

The dissolution and passivation of pure Cu and Cu-5 wt pct Ag anodes in H{sub 2}SO{sub 4}-CuSO{sub 4} electrolyte were investigated by a direct observation method that combined the techniques of optical microscopy and channel flow double electrode. Linear sweep voltammetry of the anodes showed that the dissolution of Cu transited from the charge transfer-controlled reaction to the mass transfer-controlled reaction, followed by the passivation of the electrodes. The direct observation of the pure Cu anode revealed that Cu particles were generated on the surface and the particles fell away during passivation. On the other hand, a slime layer of Ag particles that adhered to the surface was generated during the dissolution of the Cu-5 wt pct Ag anode. The Cu-5 wt pct Ag anode was passivated with a lower current density than the pure Cu anode, which suggested that the morphology and adhesive characteristics of the slime on the anode affected the passivation. The direct observation method described herein is useful for understanding reactions on electrodes that undergo drastic changes in their surface morphology. Information obtained from this method can help with the development of new processes for the effective utilization of limited natural resources and energy, such as the recycling of Cu by electrorefining.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Electrolytic Synthesis of Ni-W-MWCNT Composite Coating for Alkaline Hydrogen Evolution Reaction

Nickel–tungsten multi-walled carbon nanotube (Ni-W-MWCNT) composite films were fabricated by an electrodeposition technique, and their electrocatalytic activity toward hydrogen evolution reaction (HER) was studied. Ni-W-MWCNT composite films with a homogeneous dispersion of MWCNTs were deposited from an optimal Ni-W plating bath containing functionalized MWCNTs, under galvanostatic condition. The presence of functionalized MWCNT was found to enhance the induced codeposition of the reluctant metal W and resulted in a W-rich composite coating with improved properties. The electrocatalytic behaviors of Ni-W-MWCNT composite coating toward HER were studied by cyclic voltammetry (CV) and chronopotentiometry techniques in 1.0 M KOH medium. Further, Tafel polarization and electrochemical impedance spectroscopy (EIS) studies were carried out to establish the kinetics of HER on the alloy and composite electrodes. The experimental results revealed that the addition of MWCNTs (having a diameter of around 10-15 nm) into the alloy plating bath has a significant effect on the electrocatalytic behavior of Ni-W alloy deposit. The Ni-W-MWCNT composite coating was found to show better HER activity than the conventional Ni-W alloy coating. The enhanced electrocatalytic activity of Ni-W-MWCNT composite coating is attributed to the MWCNT intersticed in the deposit matrix, evidenced by surface morphology, composition and phase structure of the coating through SEM, EDS and XRD analyses, respectively.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Preparation and Characterization of Silanes Films to Protect Electrogalvanized Steel

Silanes are an interesting alternative to chromate-based surface treatments for temporary protection of electrogalvanized steel. In this work, the protective behavior of 3-mercaptopropyltrimethoxysilane (MTMO), 3-aminopropyltriethoxysilane (AMEO), or 3-glycidoxypropyltrimethoxysilane (GLYMO) films applied on electrogalvanized automotive quality steel sheets has been studied. The silane coating morphology, composition, and porosity were characterized by scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), x-ray fluorescence, immersion in copper sulfate, and cyclic voltammetry. The corrosion protection was evaluated by polarization curves, electrochemical noise measurements, electrochemical impedance spectrometry, and accelerated humidity chamber tests. The results showed that the silanes protect temporarily electrogalvanized steel from corrosion. MTMO forms a relatively thick and cracked film. AMEO and GLYMO films were so thin that they could not be observed by SEM but silicon was detected by EDS. MTMO provided good temporary protection, being an alternative to replace Cr(VI) as protector of electrogalvanized steel.

36 MATERIALS SCIENCE↗
DOE OSTI2019

On the Use of Voltammetry to Estimate the Effectiveness of Cathodic Protection of Buried Steel Structures

Buried steel structures, e.g., oil and gas pipelines, are often protected against corrosion by the combination of organic coating and cathodic protection. The effectiveness of cathodic protection can be monitored over time using voltammetry via a computer fitting of the polarization curves with theoretical electrochemical kinetic laws. In this study, the influence of the scan rate and the procedure used for the acquisition of the polarization curve was investigated. Reliable, though slightly overestimated, residual corrosion rates were obtained using a specific procedure and a low potential scan rate. However, the residual corrosion rate has a meaning only if the wet area of the electrode is known, which can be achieved by measuring another parameter linked to the wet area, e.g., the electrolyte resistance R{sub s}. In a soil at 25% saturation, the wet area, which is the surface of the metal in contact with the soil electrolyte, may be actually significantly different from the whole surface of the electrode.

36 MATERIALS SCIENCE↗
DOE OSTI2019

In situ Preparation of HNbMoO{sub 6}/C Nanocomposite for Sensitive Detection of Clenbuterol

In this paper, we synthesized HNbMoO{sub 6}/C composite through the calcination of octylamine-intercalated HNbMoO{sub 6} precursor. The resulting HNbMoO{sub 6}/C composite showed some new phases of MoO{sub 2}, MoO{sub 3}, NbO{sub 2}, Nb{sub 2}O{sub 5}, and carbon, which was fully confirmed via powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and X-ray photoelectron spectroscopy (XPS) technologies. Besides, the HNbMoO{sub 6}/C hybrid was coated on glass carbon electrode to construct an electrochemical sensor for sensitive determination of clenbuterol. The electrochemical behaviors of clenbuterol on the prepared electrode were tested by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) analysis. The results showed that the intercalated carbon can act as active sites to accelerate electron transfer. In addition, more exposed surface areas of the HNbMoO{sub 6}/C composite will facilitate the electrolyte to permeate. The oxidation peak current of clenbuterol was linearly related to its concentration in the range of 1.04 × 10{sup −5} to 7.51 × 10{sup −4} mol L{sup −1}, and the determination limit was calculated to be 3.03 × 10{sup −6} mol L{sup −1} (S/N = 3). This sensor exhibits excellent stability, reproducibility, specificity, and good recoveries when applied to monitor clenbuterol in real samples.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

One-step construction of a molybdenum disulfide/multi-walled carbon nanotubes/polypyrrole nanocomposite biosensor for the ex-vivo detection of dopamine in mouse brain tissue

Highlights: • Ex vivo dopamine detection in mouse brain tissues of Parkinson's disease model. • Nanocomposite constructed by one-step electrochemical approach. • The synergetic performance enhancement of the sensor by nanocomposite. We developed a new strategy for construction of a biosensor for the neurotransmitter dopamine. The biosensor was constructed by one-step electrochemical deposition of a nanocomposite in aqueous solution at pH 7.0, consisting of molybdenum disulfide, multi-walled carbon nanotubes, and polypyrrole. A series of analytical methods was performed to investigate the surface characteristics and the improved electrocatalytic effect of the nanocomposite, including cyclic voltammetry, electrochemical impedance spectroscopy, field-emission scanning electron microscopy, atomic force microscopy, and Raman spectroscopy. The constructed biosensor showed high sensitivity (1.130 μAμM{sup −1}cm{sup −2}) with a dynamic linearity range of 25–1000 nM and a detection limit of 10 nM. Additionally, the designed sensor exhibited strong anti-interference ability and satisfactory reproducibility. The practical application of the sensor was manifested for the ex vivo determination of dopamine neurotransmitters using brain tissue samples of a mouse Parkinson's disease model.

60 APPLIED LIFE SCIENCES↗