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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Carbon-Fuelled Future

Whether due to changes in policy or consumption of available fossil fuels, alternative sources of energy will be required, especially given the rising global energy demand. However, one of the main factors limiting the widespread utilization of renewable energy, such as wind, solar, wave or geothermal, is our ability to store energy. Storage of energy from carbon-neutral sources, such as electricity from solar or wind, can be accomplished through many routes. One approach is to store energy in the form of chemical bonds, as fuels. The conversion of low-energy compounds, such as water and carbon dioxide, to higher energy molecules, such as hydrogen or carbon-based fuels, enables the storage of carbon-neutral energy on a very large scale. The author¹s work in this area is supported by the US Department of Energy Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

CO2 reduction renewable energy↗
DOE OSTI2013

Electrocatalytic Oxidation of Formate with Nickel Diphosphane Dipeptide Complexes. Effect of Ligands Modified with Amino Acids

A series of nickel bis-diphosphine complexes with dipeptides appended to the ligands were investigated for the catalytic oxidation of formate. Typical rates of ~7 s -1 were found, similar to the parent complex (~8 s -1 ), with amino acid size and positioning contributing very little to rate or operating potential. Hydroxyl functionalities did result in lower rates, which were recovered by protecting the hydroxyl group. The results suggest that the overall dielectric introduced by the dipeptides does not play an important role in catalysis, but free hydroxyl groups do influence activity suggesting contributions from intra- or intermolecular interactions. These observations are important in developing a fundamental understanding of the affect that an enzyme-like outer coordination sphere can have upon molecular catalysts. This work was funded by the US DOE Basic Energy Sciences, Chemical Sciences, Geoscience and Biosciences Division (BRG, AJ, AMA, WJS), the US DOE Basic Energy Sciences, Physical Bioscience program (MLR). Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

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

A Ni(II) Bis(diphosphine)-Hydride Complex Containing Proton Relays - Structural Characterization and Electrocatalytic Studies

The syntheses of the new 1,5-diphenyl-3,7-di(isopropyl)-1,5-diaza-3,7-diphosphacyclooctane ligand, PiPr2NPh2, is reported. The two equivalents of the ligand react with [Ni(CH3CN)6](BF4)2 to form the bis-diphosphine Ni(II)-complex [Ni(PiPr2NPh2)2](BF4)2, which acts as a proton reduction electrocatalyst. In addition to [Ni(PiPr2NPh2)2]2+, we report the syntheses and structural characterization of the Ni(0)-complex Ni(PiPr2NPh2)2, and the Ni(II)-hydride complex [HNi(PiPr2NPh2)2]BF4. The [HNi(PiPr2NPh2)2]BF4 complex represents the first Ni(II)-hydride in the [Ni(PR2NR'2)2]2+ family of compounds to be isolated and structurally characterized. In addition to the experimental data, the mechanism of electrocatalysis facilitated by [Ni(PiPr2NPh2)2]2+ is analyzed using linear free energy relationships recently established for the [Ni(PR2NR'2)2]2+ family. We thank Dr. Aaron Appel, Dr. Simone Raugei and Dr. Eric Wiedner for helpful discussions. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Mass spectrometry was provided at W. R. Wiley Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the Department of Energy’s office of Biological and Environmental Research located at Pacific Northwest National Laboratory. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

diphosphine↗
DOE OSTI2016

Synthesis and Structure of Vanadium Halide Complexes Containing Diphosphine Ligands with Pendant Amines

A series of vanadium(III) diiodide complexes of the formula CpV(P R N R' P R )I 2 (Cp = 5-C 5 H 5 ; P R N R' P R = (R 2 PCH 2 ) 2 N(R)), where R = Et, R = Me (1a), R = Ph (1b); R = Ph, R = Me (1c)) is reported. The corresponding vanadium(II) monoiodide complexes of the formula CpV(P R N R' PR )I, where R = Et, R = Me (2a), R = Ph (2b); R = Ph, R = Me (2c)) were prepared in THF by reduction of 1a-c with Zn powder. The paramagnetic complexes 1a-c and 2a-c are characterized by elemental analysis, 1H NMR spectroscopy, and by cyclic voltammetry for complexes 2b and 4b. Complexes 1c and 2a-c were also characterized in the single crystal by X-ray crystallography. We report the preparation of the vanadium(II) complexes CpV(P Ph 2 N Ph 2 )I (3) (P Ph 2 N Ph 2 = 1,5-diphenyl-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane) and trans-[VCl 2 (PEtNMePEt)2] (4a) and trans-[VCl 2 (PEtNPhPEt) 2 ] (4b). These complexes represent initial coordination chemistry of vanadium complexes with P R N R' P R and P Ph 2 N Ph 2 diphosphine ligands, which contain a pendant amine in the second coordination sphere. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

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

Material Profile Influences in Bulk-Heterojunctions

he morphology in mixed bulk-heterojunction films are compared using three different quantitative measurement techniques. We compare the vertical composition changes using high-angle annular dark-field scanning transmission electron microscopy with electron tomography and neutron and x-ray reflectometry. The three measurement techniques yield qualita-tively comparable vertical concentration measurements. The presence of a metal cathode during thermal annealing is observed to alter the fullerene concentration throughout the thickness of the film for all measurements. However, the abso-lute vertical concentration of fullerene is quantitatively different for the three measurements. The origin of the quantitative measurement differences is discussed. The authors thank Luna Innovations, Inc. for donating the endohedral fullerenes used in this study and Plextronics for the P3HT. They are gratefully thank the National Science Foundation Energy for Sustainability Program, Award No. 0933435. This work benefited from the use of the Lujan Neutron Scattering Center at Los Alamos Neutron Science Center funded by the DOE Office of Basic Energy Sciences and Los Alamos National Laboratory under DOE Contract DE-AC52-06NA25396. This research was also supported in part by Laboratory Directed Research & Development program at PNNL. The Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy under contract DE-AC05-76RL01830.

blends↗
DOE OSTI2015

Synthesis and Protonation Studies of Molybdenum(0) Bis(dinitrogen) Complexes Supported by Diphosphine Ligands Containing Pendant Amines

A series of molybdenum bis(dinitrogen) complexes of the formula trans-Mo(N2)2(PEtNRPEt)2 (PEtNRPEt = Et2PCH2N(R)CH2Et2; R = phenyl (1), 2,6-difluorobenzyl (2), 3,5-difluorobenzyl (3), CH2CH2NMe2 (4), CH2-o-Py (5)) have been synthesized and characterized by NMR and IR spectroscopy, and X-ray crystallography. Protonation studies with stoichiometric amounts of triflic acid (HOTf) were performed and the the protonated products were characterized by NMR and in situ IR spectroscopic methods. Protonolysis experiments with excess triflic acid were conducted to test for the formation of ammonia from reduction of the dinitrogen ligands. This work was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy Office of Science, Office of Basic Energy Sciences. S.L. was supported by the DOE Office of Science, Early Career Research Program through the Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for DOE.

ammonia↗
DOE OSTI2014

Molecular Dynamics Study of the Proposed Proton Transport Pathways in [FeFe]-Hydrogenase

Possible proton channels in Clostridium pasteurianum [FeFe]-hydrogenase were investigated with molecular dynamics simulations. This study was undertaken to discern proposed channels, compare their properties, evaluate the functional channel, and to provide insight into the features of an active proton channel. Our simulations suggest that protons are not transported through water wires. Instead, a five-residue motif (E282, S319, E279, HOH, C299) was found to be the likely channel, consistent with experimental observations. This channel connects the surface of the enzyme and the di-thiomethylamine bridge of the catalytic H-cluster, permitting the transport of protons. The channel was found to have a persistent hydrogen bonded core (residues E279 to S319), with less persistent hydrogen bonds at the ends of the channel. The hydrogen bond occupancy in this network was found to be sensitive to the protonation state of the residues in the channel, with different protonation states enhancing or stabilizing hydrogen bonding in different regions of the network. Single site mutations to non-hydrogen bonding residues break the hydrogen bonding network at that residue, consistent with experimental observations showing catalyst inactivation. In many cases, these mutations alter the hydrogen bonding in other regions of the channel which may be equally important in catalytic failure. A correlation between the protein dynamics near the proton channel and the redox partner binding regions was also found as a function of protonation state. The likely mechanism of proton movement in [FeFe]-hydrogenases is discussed based on the structural analysis presented here. This work was funded by the DOE Office of Science Early Career Research Program through the Office of Basic Energy Sciences. Computational resources were provided at W. R. Wiley Environmental Molecular Science Laboratory (EMSL), a national scientific user facility sponsored by the Department of Energy’s Office of Biological and Environmental Research located at Pacific Northwest National Laboratory, and a portion of the research was performed using PNNL Institutional Computing at Pacific Northwest National Laboratory. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

biomimetics↗
DOE OSTI2011

Effects of heat and mass transfer on the kinetics of CO oxidation over RuO2(110) catalyst

By combining first-principles kinetic Monte Carlo (KMC) simulation with a second-order finite difference continuum model, a hybrid computational model is developed to study the effects of heat and mass transfer in the surrounding gas phase on the heterogeneous reaction kinetics. The integrated computational framework consists of a surface phase where catalytic surface reactions occur and a gas-phase boundary layer imposed on the catalyst surface where the temperature and pressure gradients exist. The temperature and pressure gradients in the gas-phase boundary layer are the consequence of thermal and molecular diffusions of reactants and products under reaction conditions. The surface phase domain is modeled using the site-explicit first-principles KMC simulation. The gas-phase boundary layer domain is described using the grid-based Crank-Nicolson method. At each time step, the heat and mass fluxes between two domains are calculated simultaneously until the steady-state reaction condition is reached. At the steady-state reaction condition, the activity, the surface coverages of reaction intermediates, as well as the temperature and pressure gradient profiles in the gas-phase boundary layer are statistically constant with very small fluctuations. To demonstrate the idea that the proper consideration of heat and mass transfer in the reaction environment is essential to accurate measurement of the intrinsic reaction kinetics, we investigated the kinetics of CO oxidation over the RuO2(110) catalysts. By varying the thickness of the RuO2(110) catalyst, the pronounced temperature and pressure gradients are formed in the gas-phase boundary layer. Our simulation results indicate that the temperature and pressure gradients caused by the heat and mass transfer could dramatically affect the observed intrinsic reaction kinetics under presumed nominal operating reaction conditions. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

Characterization and Mechanistic Studies of the Dehydrogenation of NHxBHx Materials

In this review we cover the recent developments providing insight into the chemical and physical properties for a series of hydrogen-rich NBHx materials that are of interest as energy storage media for fuel cell power applications. These materials, ammonium borohydride (ABH2, [NH4][BH4]; 240 g H2/kg; 165 g/liter), ammonia borane (AB, [NH3BH3]; 196 g H2/kg; 147 g/liter) and diammoniate of diborane (DADB, [NH3BH2NH3][BH4]; 196 g H2/kg; ca. 151 g/liter), release hydrogen by a series of moderately exothermic reaction pathways. The advantage of these materials is that hydrogen release is kinetically controlled and occurs at relatively low temperatures and moderate pressures. The challenges are devising economical pathways to regenerate the fully charged hydrogen storage materials off board and understanding and controlling the formation of volatile impurities that decrease the purity of the hydrogen available for polymer electrolyte membrane fuel cell applications. The focus of this review is on the solid phase ABH2, AB and DADB materials to complement the coverage of AB in other recent review articles [1-2]. Additional discussion is given on the decomposition products of these materials, polyaminoborane (PAB, [NH2BH2]n) and polyiminoborane (PIB, [NHBH]n). The article is organized into 3 sections, (i) Synthesis and stuctural characterization; (ii) Kinetics and thermodynamics of hydrogen release and (iii) Outstanding challenges for breakthroughs. This work was supported by the US Department of Energy Basic Energy Sciences' Chemical Sciences, Geosciences & Biosciences Division. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

08 HYDROGEN↗
DOE OSTI2011

Molecular mechanism of hydrocarbons binding to the metal–organic framework

The adsorption and diffusivity of methane, ethane, n-butane, n-hexane and cyclohexane in a metal organic framework (MOF) with the organic linker tetrakis[4-(carboxyphenyl)oxamethyl]methane, the metal salt, Zn2+, and organic pillar, 4,4’-bipyridin was studied using molecular dynamics simulations. For the n-alkanes, the longer the chain, the lower the free energy of adsorption, which was attributed to a greater number of contacts between the alkane and MOF. Cyclohexane had a slightly higher adsorption free energy than n-hexane. Furthermore, for cyclo- and n-hexane, there were no significant differences in adsorption free energies between systems with low to moderate loadings. The diffusivity of the n-alkanes was found to strongly depend on chain length with slower diffusion for longer chains. Cyclohexane had no effective diffusion, suggesting that the selectivity the MOF has towards n-hexane over cyclohexane is the result of kinetics instead of energetics. This work was supported by the U.S. Department of Energy's (DOE) Office of Basic Energy Sciences, Chemical Sciences program. The Pacific Northwest National Laboratory is operated by Battelle for DOE.

03 NATURAL GAS↗
DOE OSTI2012

Group 10 complexes containing phosphinomethylamine ligands: Synthesis, structural analysis and electrochemical studies

The reaction of [M(triphos)OTf](OTf) (M = Pd, Pt; triphos = (Ph2PCH2CH2)2PPh; OTf = triflate) with one equivalent of a diphenylphosphinomethylamine ligand (PPh2NPh(R), R = Ph or Me) leads to the formation of the M(II) complexes [Pd(triphos)PPh2NPh(R)](OTf)2 (1a, R = Ph; 1b, R = Me) and [Pt(triphos)PPh2NPh(R)]- (OTf)2 (2a, R = Ph; 2b, R = Me). Complexes 1a, 1b, 2a and 2b were obtained in moderate yields and characterized by elemental analysis, 1H, 13C, 31P NMR and X-ray diffraction. The redox behavior of these complexes shows a reversible reduction wave with half-wave potentials ranging from -1.04 to -1.23 V. Electrocatalytic proton reduction studies demonstrate these complexes function as hydrogen production catalysts with turn over frequencies ranging from 120 to 200 s-1. We thank Research Corporation Cottrell Science Award (7293) and Fort Lewis College for financial support of this project. Pacific Northwest National Laboratory collaborators would like to acknowledge the support of the US Department of Energy Basic Energy Sciences’ Chemical Sciences, Geosciences, and Biosciences Division. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

08 HYDROGEN↗
DOE OSTI2012

Biologically Inspired Phosphino Platinum Complexes

Platinum complexes containing phosphino amino acid and amino acid ester ligands, built upon the PPhNR’2 platform, have been synthesized and characterized (PPhNR’2= [1,3-diaza]-5-phenyl phosphacyclohexane, R’=glycine or glycine ester). These complexes were characterized by 31P, 13C, 1H, 195Pt NMR spectroscopy and mass spectrometry. The X-ray crystal structure of one of the complexes, [PtCl2(PPhNGlyester 2)2], is also reported. These biologically inspired ligands have potential use in homogeneous catalysis, with special applications in chiral chemistry and water soluble chemistry. These complexes also provide a foundation upon which larger peptides can be attached, to allow the introduction of enzyme-like features onto small molecule catalysts. This work was supported by the US Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2011

Insight into methanol synthesis from CO2 hydrogenation on Cu(111): Complex reaction network and the effects of H2O

Methanol synthesis from CO2 hydrogenation on supported Cu catalysts is of considerable importance in the chemical and energy industries. Although extensive experimental and theoretical efforts have been carried out in the past decades, the most fundamental questions such as the reaction mechanisms and the key reaction intermediates are still in debate. In the present work, a comprehensive reaction network for CO2 hydrogenation to methanol on Cu(111) was studied using periodic density functional theory (DFT) calculations. All of the elementary reaction steps in the reaction network were identified in an unbiased way with the dimer method. Our calculation results show that methanol synthesis from direct hydrogenation of formate on Cu(111) is not feasible due to the high activation barriers for some of the elementary steps. Instead, we find that CO2 hydrogenation to hydrocarboxyl (trans-COOH) is kinetically more favorable than formate in the presence of H2O via a unique proton transfer mechanism. The trans-COOH is then converted into hydroxymethylidyne (COH) via dihydroxycarbene (COHOH) intermediates, followed by three consecutive hydrogenation steps to form hydroxymethylene (HCOH), hydroxymethyl (H2COH), and methanol. This is consistent with recent experimental observations [1], which indicate that direct hydrogenation of formate will not produce methanol under dry hydrogen conditions. Thus, both experiment and computational modeling clearly demonstrate the important role of trace amounts of water in methanol synthesis from CO2 hydrogenation on Cu catalysts. The proposed methanol synthesis route on Cu(111) not only provides new insights into methanol synthesis chemistry, but also demonstrates again that spectroscopically observed surface species are often not critical reaction intermediates but rather spectator species. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

08 HYDROGEN↗
DOE OSTI2013

Hydrodechlorination Catalysis of Pd-on-Au Nanoparticles Varies with Particle Size

The dependence of bimetallic PdAu catalytic activity on the relative ratios of Pd and Au has been theoretically predicted and experimentally observed for a number of reactions. Trichloroethene (TCE), a common carcinogenic solvent that is difficult to remove from contaminated groundwater in many industrialized nations, can be chemically degraded especially rapidly with Au nanoparticles partially coated with Pd ("Pd-on-Au NPs"). These NPs catalyze the room-temperature water-phase TCE hydrodechlorination (HDC) reaction with activities that follow a volcano-shape dependence on Pd surface coverage. The effect of particle size is not known, though. Pd-on-Au NPs synthesized with 3, 7, and 10 nm Au NPs and Pd surface coverages between 0 and 150% were studied in detail. Volcano-shape dependence on Au particle size and Pd surface coverage was observed, with 7 nm Au NPs with a Pd coverage of 60-70% having the highest TCE HDC activity. Extended x-ray absorption fine-structure spectroscopy (EXAFS) revealed the correlation was strongest between catalytic activity and the presence of non-oxidized Pd ensembles of ~2-3 atoms in contact with ~8-10 Au atoms. Isolated Pd atoms and Pd ensembles were visualized for the first time through aberration-corrected scanning transmission electron microscopy (STEM). This study provides the most direct evidence yet for Pd-on-Au NPs containing 2-dimensional Pd ensembles as the active sites for TCE HDC and likely for other chemical reactions. A portion of the research was performed using EMSL, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. This research was supported by the Laboratory Directed Research and Development program at Pacific Northwest National Laboratory. The Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

catalysis↗
DOE OSTI2012

Visible Light Induced Photodesorption of NO from the α-Cr2O3(0001) Surface

Nitric oxide chemistry and photochemistry on the Cr-terminated surface of α-Cr2O3(0001) was examined using temperature programmed desorption (TPD), sticking coefficient measurements and photodesorption. NO adsorbed at 100 K binds at surface Cr cation sites forming a strongly bound surface species that thermally desorbs at 320-340 K, depending on coverage. No thermal decomposition was detected in TPD in agreement with previous results in the literature. Sticking probability measurements of NO at 100 K indicated near unity sticking for NO coverages up to ~1.3 ML, with additional adsorption with higher exposures at decreased sticking probability. These results suggest that each surface Cr cation site on the α-Cr2O3(0001) surface was capable of binding more than one NO molecule, although it is unclear whether this was as separate NO molecules or as dimers. Photodesorption of adsorbed NO was examined for surface coverages below the 1 ML point. Both visible and UV light were shown to photodesorb NO without detectable NO photodecomposition. Visible light photodesorption of NO occurred with a cross section of ~2x10-19 cm2, which was estimated to greater than that obtained with UV light. The visible light photodesorption event was not associated with bandgap excitation in α-Cr2O3(0001), but instead was linked to excitation of a surface Cr3+-NO- charge transfer complex. These results illustrate that localized photoabsorption events at surface sites with unique optical properties (relative to the bulk) can result in unexpected surface photochemistry. This work was supported by the US Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Single-Amino Acid Modifications Reveal Additional Controls on the Proton Pathway of [FeFe]-Hydrogenase

The proton pathway of [FeFe]-hydrogenase is essential for enzymatic H2 production and oxidation and is composed of four residues and a modeled water molecule. Recently, a computational analysis of this pathway revealed that the solvent-exposed residue of the pathway (Glu282) could form hydrogen bonds to two residues outside of the pathway (Arg286 and Ser320), implicating that these residues could function in regulating proton transfer. Substituting Arg286 with leucine eliminates hydrogen bonding with Glu282 and results in a 2.5-fold enhancement in H2 production activity, suggesting that Arg286 serves an important role in controlling the rate of proton delivery. In contrast, substitution of Ser320 with alanine reduces the rate approximately 5-fold, implying that it either acts as a member of the pathway or influences Glu282 to enable proton transfer. Interestingly, QM/MM and molecular dynamics calculations indicate that Ser320 does not play an electronic or structural role. QM calculations also estimate that including Ser320 in the pathway does not significantly change the barrier to proton movement, providing further support for its role as a member of the proton pathway. While further studies are needed to quantify the role of Ser320, collectively, these data provide evidence that the enzyme scaffold plays a significant role in modulating the activity of the enzyme, demonstrating that the rate of intraprotein proton transfer can be accelerated, particularly in a non-biological context. This work was supported by the DOE Great Lakes Bioenergy Research Center (DOE BER Office of Science, DE-FC02-07ER64494). In addition, support from the DOE Office of Science Early Career Research Program through the Office of Basic Energy Sciences (WJS, BGP, SR) is gratefully acknowledged. Computational resources were provided at W. R. Wiley Environmental Molecular Science Laboratory (EMSL), a national scientific user facility sponsored by the Department of Energy’s Office of Biological and Environmental Research located at Pacific Northwest National Laboratory, and a portion of the research was performed using PNNL Institutional Computing at Pacific Northwest National Laboratory. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

catalysis↗