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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 OSTI2016

Overview of the U.S. DOE Hydrogen Safety, Codes and Standards Program. Part 4: Hydrogen Sensors; Preprint

Hydrogen sensors are recognized as a critical element in the safety design for any hydrogen system. In this role, sensors can perform several important functions including indication of unintended hydrogen releases, activation of mitigation strategies to preclude the development of dangerous situations, activation of alarm systems and communication to first responders, and to initiate system shutdown. The functionality of hydrogen sensors in this capacity is decoupled from the system being monitored, thereby providing an independent safety component that is not affected by the system itself. The importance of hydrogen sensors has been recognized by DOE and by the Fuel Cell Technologies Office's Safety and Codes Standards (SCS) program in particular, which has for several years supported hydrogen safety sensor research and development. The SCS hydrogen sensor programs are currently led by the National Renewable Energy Laboratory, Los Alamos National Laboratory, and Lawrence Livermore National Laboratory. The current SCS sensor program encompasses the full range of issues related to safety sensors, including development of advance sensor platforms with exemplary performance, development of sensor-related code and standards, outreach to stakeholders on the role sensors play in facilitating deployment, technology evaluation, and support on the proper selection and use of sensors.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2016

Flux Synthesis, Optical and Photocatalytic Properties of n -type Sn 2 TiO 4 : Hydrogen and Oxygen Evolution under Visible Light

Here, the n -type Sn 2 TiO 4 phase was synthesized using flux methods and found to have one of the smallest visible-light bandgap sizes known that also maintains suitable conduction and valence band energies for driving photocatalytic water-splitting reactions. The Sn 2 TiO 4 phase was synthesized using either a SnCl 2 flux or a SnCl 2 /SnF 2 peritectic flux in a 2:1 flux-to-precursor ratio heated at 600 and 400 °C for 24 h, respectively. The two types of salt fluxes resulted in large rod-shaped particles at 600 °C and smaller tetragonal prism-shaped particles at 400 °C. Surface photovoltage spectroscopy measurements produced a negative photovoltage under illumination >1.50 eV, which confirmed electrons as the majority charge carriers and ~1.50 eV as the effective band gap. Mott–Schottky measurements at pH 9.0 showed the conduction (–0.54 V vs NHE) and valence band (+1.01 V vs NHE) positions meet the critical thermodynamic requirements for total water splitting. The Sn 2 TiO 4 particles were deposited and annealed as polycrystalline films on FTO slides, and exhibited photoanodic currents in aqueous solutions under visible-light irradiation. The Sn 2 TiO 4 particles were also suspended in aqueous methanol solutions and irradiated with visible and ultraviolet light. The larger rod-shaped Sn 2 TiO 4 particles had the higher rates of photocatalytic hydrogen production (~11.6 μmol H 2 h –1 ) in comparison to the smaller tetragonal prism-shaped Sn 2 TiO 4 particles (~3.4 μmol H 2 h –1 ). Conversely, for photocatalytic oxygen production, the rates for the smaller tetragonal prism-shaped particles in aqueous AgNO 3 solution were slightly higher (~16.3 μmol O 2 h –1 ) than for the larger rod-shaped particles (~11.9 μmol O 2 h –1 ). Apparent quantum yields of 0.995% and 0.0098% were measured for O 2 and H 2 production, respectively, under 435 nm light.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1994

Structure of 4-methylpyridinium Hydrogen Sulfide

4-Methylpyridinium hydrogen sulfide, (C6H7NH)HS, M(sub r) = 127.21, consists of C6H7NH(+) cations and HS(-) anions. Z = 2 for the crystal with monoclinic space group Cm (#8), dimensions of a = 8.679(2) A, b = 7.964(1) A, and c = 4.860(2) A, an angle beta of 101.10(2) degrees, and a volume of V = 329.6(3) A(exp 3). R = 0.039 and R(sub w) = 0.048 for 385 reflections with F(sub o)(exp 2) greater than 3 sigma(F(sub o)(exp 2)) and 59 variables. Both the C6H7NH(+) cation and the HS(-) anion lie on crystallographic mirror planes with the N,S, two carbon atoms, and two hydrogen atoms positioned in the planes. The hydrogen atom of the HS(-) anion was not located.

Andras, Maria T.↗
DOE OSTI2026

Understanding the effect of organic coatings on 4-nitrostyrene hydrogenation selectivity over Pt/TiO 2 catalysts

The hydrogenation of 4-nitrostyrene was investigated over Pt/TiO 2 catalysts to understand the effects of different catalyst coatings on product selectivity and reaction rates. This reaction is a much-investigated selectivity probe due to difficulty in controlling reactivity between the nitro and vinyl groups of 4-nitrostyrene, with C=C reduction generally being more favorable. 4-Nitrostyrene hydrogenation reactions were carried out in a batch reactor using uncoated, organothiol coated, phosphonic acid (PA) coated, and ion-conducting polymer (ionomer) coated catalysts. Thiols form dense coatings on Pt surfaces, whereas PAs preferentially accumulate on TiO 2 ; ionomer binding preference is unknown for this type of catalyst. The coating densities of the thiols and PAs were varied to observe the effects of loading on catalytic activity and reaction selectivity relative to the uncoated catalyst. Changes in selectivity were observed for catalysts with all coatings, with thiol coatings shifting selectivity towards the nitro reduction product, 4-vinylaniline (4-VA), and both ionomer and PA coatings shifting towards 4-ethylnitrobenzene, the olefin hydrogenation product. It was observed that selectivity toward 4-VA increased with thiol coating density, where 1,2-benzenedithiol (BDT) coated catalysts exhibited a selectivity of >99%. These changes were attributed to the identity of the adsorption sites blocked by the different coatings: blocking of metal sites via thiols decreased the rate of C=C hydrogenation, whereas blocking of TiO 2 sites by PAs decreased the rate of nitro group hydrogenation. The changes observed for ionomer and PA coatings suggested that ionomers, like PAs, bind preferentially to the metal oxide support rather than the active metal. This work provides new support to the proposal that nitro group hydrogenation preferentially occurs on TiO 2 sites after hydrogen spillover and underscores how selection of ligand functionality can be used to tune catalyst selectivity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Direct production of OH radicals upon CH overtone activation of (CH{sub 3}){sub 2}COO Criegee intermediates

Ozonolysis of alkenes, a principle non-photolytic source of atmospheric OH radicals, proceeds through unimolecular decay of energized carbonyl oxide intermediates, known as Criegee intermediates. In this work, cold dimethyl-substituted Criegee intermediates are vibrationally activated in the CH stretch overtone region to drive the 1,4 hydrogen transfer reaction that leads to OH radical products. IR excitation of (CH{sub 3}){sub 2}COO reveals the vibrational states with sufficient oscillator strength, coupling to the reaction coordinate, and energy to surmount the effective barrier (≤ 16.0 kcal mol{sup −1}) to reaction. Insight on the dissociation dynamics is gleaned from homogeneous broadening of the spectral features, indicative of rapid intramolecular vibrational energy redistribution and/or reaction, as well as the quantum state distribution of the OH X{sup 2}Π (v = 0) products. The experimental results are compared with complementary electronic structure calculations, which provide the IR absorption spectrum and geometric changes along the intrinsic reaction coordinate. Additional theoretical analysis reveals the vibrational modes and couplings that permit (CH{sub 3}){sub 2}COO to access to the transition state region for reaction. The experimental and theoretical results are compared with an analogous recent study of the IR activation of syn-CH{sub 3}CHOO and its unimolecular decay to OH products [F. Liu, J. M. Beames, A. S. Petit, A. B. McCoy, and M. I. Lester, Science 345, 1596 (2014)].

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

MILLIMETER-WAVE SPECTRAL LINE SURVEYS TOWARD THE GALACTIC CIRCUMNUCLEAR DISK AND Sgr A*

We have performed unbiased spectral line surveys at the 3 mm band toward the Galactic circumnuclear disk (CND) and Sgr A* using the Nobeyama Radio Observatory 45 m radio telescope. The target positions are two tangential points of the CND and the direction of Sgr A*. We have obtained three wide-band spectra that cover the frequency range from 81.3 GHz to 115.8 GHz, detecting 46 molecular lines from 30 species, including 10 rare isotopomers and 4 hydrogen recombination lines. Each line profile consists of multiple velocity components which arise from the CND, +50 km s{sup –1} and +20 km {sup –1} giant molecular clouds (GMCs), and the foreground spiral arms. We define the specific velocity ranges that represent the CND and the GMCs toward each direction, and classify the detected lines into three categories: the CND, GMC, HBD types, based on the line intensities integrated over the defined velocity ranges. The CND and GMC types are the lines that mainly trace the CND and the GMCs, respectively. The HBD types possesses the both characteristics of the CND and GMC types. We also present lists of line intensities and other parameters, as well as intensity ratios, which must be useful to investigate the difference between the nuclear environments of our Galaxy and others.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1977

The pristine nature of comets

Abundance considerations suggest that comets are likely to be the most pristine minor bodies in the solar system. In proportion to solar abundances, the present scanty data suggest that cometary oxygen is not depleted, whereas carbon is by a factor of 4 and hydrogen, by a factor of 2000. This implies that comets are less depleted in H, C, N, O than CI chondrites, namely 10:1 in hydrogen, 4:1 in carbon and 3:1 in oxygen. These results have been obtained by using dust-to-gas ratios in comets to measure the relative abundance of silicon and metals to volatile material, and the spectra of atomic lines, mainly from the vacuum ultraviolet, to determine the H/O and C/O ratios of the mixture of volatile molecules.

Delsemme, A. H.↗
DOE OSTI2016

Small-Angle Neutron Scattering Measurements of the δ Deuteride Phase in Zircaloy 4

Hydrogen pickup by Zr-based LWR fuel cladding during service leads to the formation of circumferential hydride platelet particles embedded within the Zr matrix. The precipitation of the hydride phase occurs preferentially on the water-side due to the temperature gradient within the clad wall. The non-uniform hydride morphology is known as a rim structure. Significant tensile hoop stresses within the clad wall develop during the fuel lifetime due to fission gas release and pellet-clad mechanical interaction. One potential post-service cladding failure mechanism is delayed hydride cracking (DHC) initiated by hydride reorientation under this tensile hoop stress. As a consequence, hydride reorientation and DHC have been extensively studied over the last few decades to understand the interdependencies of tensile stress, temperature, hydride morphology, and hydrogen concentration. Much of the most recent work in this area has taken advantage of 3. generation synchrotron X-ray sources to perform in situ measurements of hydride phase stability. Neutron scattering based techniques offer unique advantages in the study of hydrogen in metals (typically with deuterium substituted for hydrogen) but are under utilized in the study of hydrides in Zr. We present small-angle neutron scattering (SANS) measurements of the deuteride phase in Zircaloy 4 (Zy4) here. The SANS measurements presented here demonstrate the sensitivity of the technique to deuteride phase particles embedded in a Zy4 matrix. Quantifiable net scattering at 50 wppm effective hydrogen concentration is derived from a subtraction of a reference sample. This demonstrates that the strong χ phase Porod scattering can be effectively eliminated, revealing the response from the deuteride phase. A similar experimental protocol using small-angle X-ray scattering (SAXS) would likely fail due to poor contrast between the hydride phase and the Zr matrix. Stated in different terms, the SAXS response would be dominated by SPP Porod scattering with unresolvable net scattering from hydride particles. (authors)

36 MATERIALS SCIENCE↗
DOE OSTI2015

Effects of indium contents on photocatalytic performance of ZnIn{sub 2}S{sub 4} for hydrogen evolution under visible light

A series of ZnIn{sub x}S{sub 4+y} (x=1.6, 2.0, 2.3, 2.6, 2.9, 3.1) photocatalysts were synthesized via a facile hydrothermal method and characterized by various analytical techniques, such as XRD, EDS, UV–vis DRS, SEM, TEM, BET and PL. The ZnIn{sub x}S{sub 4+y} photocatalysts had a similar crystal structure. With the increase of indium content, the absorption edges of ZnIn{sub x}S{sub 4+y} photocatalysts shifted to longer wavelength, their crystal sizes decreased firstly and then increased and the variation of the specific surface area and total pore volume was exactly opposite. Especially, when x=2.3, ZnIn{sub 2.3}S{sub 4+y} catalyst had smallest crystal size, largest specific surface area and total pore volume. Additionally, the morphology of ZnIn{sub x}S{sub 4+y} greatly depended on the contents of indium. The photocatalytic activity of ZnIn{sub x}S{sub 4+y} was evaluated by photocatalytic hydrogen production from water under visible light. The ZnIn{sub 2.3}S{sub 4+y} sample had the highest photocatalytic activity among these ZnIn{sub x}S{sub 4+y} photocatalysts and its hydrogen production rate was 363 μmol/g h. - Graphical abstract: First, a series of catalysts were synthesized. And then those were characterized by various analytical techniques (such as SEM). finally, The photocatalytic activity of catalyst was evaluated by photocatalytic hydrogen production from water under visible light. - Highlights: • The photocatalytic property was studied upon visible-light irradiation. • ZnIn{sub x}S{sub 4+y} photocatalysts show superior photocatalytic activity. • The catalyst of grain size, morphology and BET are related to indium content. • ZnIn{sub x}S{sub 4+y} photocatalysts were synthesized via a facile hydrothermal method.

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

Catalytic Silylation of N 2 and Synthesis of NH 3 and N 2 H 4 by Net Hydrogen Atom Transfer Reactions Using a Chromium P 4 Macrocycle

We report the first discrete molecular Cr-based catalysts for the reduction of N2. This study is focused on the reactivity of the Cr-N2 complex, trans-[Cr(N2)2(PPh4NBn4)] P4Cr(N2)2, bearing a 16-membered tetraphosphine macrocycle. The architecture of the [16]-PPh4NBn4 ligand is critical to preserve the structural integrity of the catalyst. P4Cr(N2)2 was found to mediate the reduction of N2 by three complementary reaction pathways: (1) Cr-catalyzed reduction of N2 to N(SiMe3)3 by Na and Me3SiCl affording up to 34 equiv N(SiMe3)3; (2) stoichiometric reduction of N2 by protons and electrons. For example, the reaction of cobaltocene (CoCp2) and collidinium triflate (ColH[OTf]) at room temperature to afforded 1.9 equiv of NH3, or at -78 °C to afforded a mixture of NH3 and N2H4; (3) the first example of NH3 formation from the reaction of a terminally bound N2 ligand with a traditional H atom source, TEMPOH, (2,2,6,6-tetramethylpiperidine-1-ol). We found that trans-[Cr(15N2)2(PPh4NBn4)] reacts with excess TEMPOH to afford a 1.4 equiv of 15NH3.

Kendall, Alexander J.↗
DOE OSTI2020

Particle-Scale Reduction Analysis of CuFeMnO 4 with Hydrogen for Chemical Looping Combustion

In this work CuFeMnO 4 (copper iron manganese oxide) oxygen carrier was characterized using DSC/TGA, in-situ XRD, and SEM-EDS to gain a clear elucidation of the chemical looping combustion (CLC) reactions with H2 which is a component of synthesis gas. A reaction model which best described the experimental TGA reaction data was selected from the analysis. Intrinsic rate of reaction parameters obtained from the study could be used for designing a reactor for scale-up. A model with combined contributions from nucleation and growth model and dimensional phase boundary model was found to exhibit the best correlation with the experimental data. The analysis provided validation of intrinsic reaction rates and other rate parameters.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

The effects of hydrothermal temperature on the photocatalytic performance of ZnIn{sub 2}S{sub 4} for hydrogen generation under visible light irradiation

Highlights: • The ZnIn{sub 2}S{sub 4} (120, 140, 160, 180, and 200 °C) was prepared. • The activities splitting water to hydrogen under visible light were evaluated. • The activity achieved the best when hydrothermal temperature was 160 °C. • The activity order is related to the surface morphology and surface defects. - Abstract: A series of ZnIn{sub 2}S{sub 4} photocatalysts were successfully synthesized using the hydrothermal method with different hydrothermal temperatures (120, 140, 160, 180, and 200 °C) and characterized by various analysis techniques, such as UV–vis, XRD, SEM, BET and PL. The results indicated that these photocatalysts had a similar band gap. The hydrothermal temperature had a huge influence on the properties of the photocatalysts such as the BET surface area, the total pore volume, the average pore diameter, the defects and the morphology. The photocatalytic activities of ZnIn{sub 2}S{sub 4} were evaluated based on photocatalytic hydrogen production from water under visible-light irradiation. The activity order is attributed to the coefficient of the surface morphology and the surface defects. The hydrogen production efficiency achieved the best when the hydrothermal temperature was 160 °C. On the basis of the characterization of the catalysts, the effects of the hydrothermal temperature on the photocatalytic activity of ZnIn{sub 2}S{sub 4} were discussed.

36 MATERIALS SCIENCE↗