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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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15 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Adsorbate-induced adatom formation on Au-Cu bimetallic alloys and its possible consequences for CO 2 electroreduction

The adsorbate-induced formation of sub-nanometer clusters on transition-metal single crystals observed in previous high-pressure microscopic studies hinted at the in-situ formation of unique active sites even on large nanoparticle catalysts. We propose that the adatom formation energy can be used as an energetic descriptor for the initial step toward the adsorbate-induced metal-cluster formation process. This descriptor can be efficiently computed using density functional theory (DFT) calculations and applied for screening and identification of metal catalysts where this phenomenon may play an important role in generating active sites in-situ. As a proof of concept, here, we construct an adatom formation energy database for three Au x Cu y alloys (x:y = 3:1, 1:1, or 1:3) and eighteen adsorbates (H, C, N, O, F, S, Cl, Br, I, CH x , NH x (x = 1 – 3), CO, NO, and OH) commonly involved in catalytic reactions. The energetics of adatom formation were examined in all cases where the (111) terrace, (211) step-edge, and (874) kink were the sources of the adatom. We demonstrate that the presence of an adsorbate could alter not only the energetics for adatom formation but also the elemental nature of the preferred adatom being formed. Using our database, we identified promising systems which favor adsorbate-induced adatom formation under near-ambient conditions. Specifically, CO-induced adatom formation on all three Au-Cu alloy surfaces could occur under CO 2 electroreduction (CO 2 RR) conditions. This phenomenon offers a qualitative explanation for the experimentally observed CO 2 RR activity on Au-Cu alloy catalysts. As a result, our methodology offers an easily expandable and efficient approach for large-scale catalyst screening with regards to adatom/cluster formation under reaction conditions and provides insight into the possible nature of active sites on alloy catalysts from a novel perspective.

Active site↗
NASA NTRS1975

Oxygen reduction of several gold alloys in 1-molar potassium hydroxide

With rotated disk-and-ring equipment, polarograms and other electrochemical measurements were made of oxygen reduction in 1-molar potassium hydroxide on an equiatomic gold-copper (Au-Cu) alloy and a Au-Cu alloy doped with either indium (In) or cobalt (Co) and on Au doped with either nickel (Ni) or platinum (Pt). The results were compared with those for pure Au and pure Pt. The two-electron reaction dominated on all Au alloys as it did on Au. The polarographic results at lower polarization potentials were compared, assuming exclusively a two-step reduction. A qualified ranking of cathodic electrocatalytic activity on the freshly polished reduced disks was indicated: anodized Au Au-Cu-In Au-Cu Au-Cu-Co is equivalent or equal to Au-Pt Au-Ni. Aging in distilled water improved the electrocatalytic efficiency of Au-Cu-Co, Au-Cu, and (to a lesser extent) Au-Cu-In.

Miller, R. O.↗
DOE OSTI2022

Brazing characteristics, microstructure, and wettability of laser powder bed fusion additive manufactured GRCop-84 compared to CuCrZr and OFC, and brazing to titanium-zirconium-molybdenum alloy limiters

Laser Powder Bed Fusion (L-PBF) of Glenn Research Copper 84 (GRCop-84), a Cr 2 Nb (8 at. % Cr, 4 at. % Nb) precipitation hardened alloy, produces a fully dense, high conductivity alloy with a yield strength of 500 MPa and ultimate tensile strength (UTS) of 740 MPa with 20% elongation; superior to other competing copper alloys. Braze wetting characteristics of GRCop-84 with Ag-Cu-X, and Au-Cu brazes were similar to CuCrZr, but less than oxygen free copper. No difference in wetting was observed between infill and surface contour areas in L-PBF GRCop-84. Wet sanding to 240 grit (R a =0.24 µm) was considered the optimal surface condition. Silver diffusing through GRCop-84 depleted Cr 2 Nb precipitates from the copper grain and deposited agglomerations of coarsened precipitates within silver-rich regions of intergranular diffusion once a density threshold was reached. Microstructure modification was minimized with 50Au-50Cu braze implying that silver caused precipitate coarsening and agglomeration, and not high temperature exposure. Coarsened precipitates were observed on the surface within braze pools implying a contribution to braze wetting. Palcusil-25, Ticusil, CuSil-ABA, and 50Au-50Cu brazes were suitable for brazing to unplated Titanium-Zirconium-Molybdenum (TZM), while sulfamate nickel plating to allows wetting with CuSil or other non-active brazes. Additionally, vacuum brazing techniques were developed to join a 1 mm thick layer of TZM to the front of additive manufactured GRCop-84 waveguides considering the brazing characteristics of both GRCop-84, TZM, and internal stress from the difference in coefficient in thermal expansion.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Gold-in-copper at low *CO coverage enables efficient electromethanation of CO 2

The renewable-electricity-powered CO 2 electroreduction reaction provides a promising means to store intermittent renewable energy in the form of valuable chemicals and dispatchable fuels. Renewable methane produced using CO 2 electroreduction attracts interest due to the established global distribution network; however, present-day efficiencies and activities remain below those required for practical application. Here we exploit the fact that the suppression of *CO dimerization and hydrogen evolution promotes methane selectivity: we reason that the introduction of Au in Cu favors *CO protonation vs. C-C coupling under low *CO coverage and weakens the *H adsorption energy of the surface, leading to a reduction in hydrogen evolution. We construct experimentally a suite of Au-Cu catalysts and control *CO availability by regulating CO 2 concentration and reaction rate. This strategy leads to a 1.6× improvement in the methane:H 2 selectivity ratio compared to the best prior reports operating above 100 mA cm -2 . We as a result achieve a CO 2 -to-methane Faradaic efficiency (FE) of (56 ± 2)% at a production rate of (112 ± 4) mA cm -2 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

IC w22_phadiagractox Highlight: Composition-dependent melting temperature of a compound [Poster]

Figure 1 displays, ambient melting points of the Au-Cu system as a function of Cu atomic percent: present model vs. experimental data from four different sources. Figure 2 displays, ambient melting points of the U-O system as a function of O atomic percent: present model vs. both experiment and quantum molecular dynamics (QMD) simulations on the stoichiometric U-O compounds.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1984

Solubility of hydrogen in metals and its effect of pore-formation and embrittlement

The effect of alloying elements on hydrogen solubility were determined by evaluating solubility equations and interaction coefficients. The solubility of dry hydrogen at one atmosphere was investigated in liquid aluminum, Al-Ti, Al-Si, Al-Fe, liquid gold, Au-Cu, and Au-Pd. The design of rapid heating and high pressure casting furnaces used in meta foam experiments is discussed as well as the mechanism of precipitation of pores in melts, and the effect of hydrogen on the shrinkage porosity of Al-Cu and Al-Si alloys. Hydrogen embrittlement in iron base alloys is also examined.

Shahani, H. R.↗
DOE OSTI2023

Chapter 14: Surface plasmon resonance enhanced artificial photosynthesis of chemical fuels for energy storage

Nanostructured noble metals such as Au, Ag, and Cu have interesting optical properties because of the oscillation motions of their surface electrons upon strong coupling with light under resonance conditions. This resonant oscillation motion of conduction electrons refers to surface plasmon resonance (SPR) and localized SPR (LSPR) when localized near the surface of a nanoparticle. The extinction spectrum of a solution of plasmonic nanoparticles has tunable wavelength responses from UV to NIR due to strong light scattering and absorption which are highly sensitive to the permittivity of the nanoparticles, their sizes and shapes, and chemical environment. Strong light scattering due to the LSPR of plasmonic nanoparticles creates a strong localized and far-field intensity capable of enhancing light absorption characteristics of a chromophore near a plasmonic surface. Engineering the chromophores’ radiative decay dynamics can be done by 1) increasing its radiative decay rate to increase its photoluminescence intensity and 2) increasing its nonradiative decay rates associated to direct charge transfer to the metal surface. Such interesting photophysical properties of a chromophore can be extended to other light-absorbing materials such as semiconductor thin films and nanostructures. This plasmonic effect on the photophysics of a light-absorbing material can be theoretically and experimentally validated. The phenomenon has also been applied to advanced optoelectronic devices such as organic light-emitting diodes (OLED)1 and organic photovoltaics (OPV).2-4 The local field created by the SPR can provide an intense EM field to enhance photoluminescence emission of an organic chromophore5-8 and Raman scattering of an organic molecule, and single-molecule Raman9-10 can be detected on specially designed LSPR substrate. (Figure 1 on SPR for energy) Recent studies suggest that LSPR can be incorporated in light-harvesting and conversion systems to increase energy conversion in a solar cell and photoelectrochemical cell and chemical transformations of CO2 to chemical fuels.11-12 Plasmonic active metals naturally exhibit catalytic activities for electrochemical fuel conversion that can be enhanced by engineering their structures to form unique catalytic structures such as symmetry-broken Au-Cu Janus nanocrystals.13 These studies are critical to addressing the global challenges of energy14-15 and CO2 emission from nonrenewable sources such as coal, petroleum, and natural gas.16-17 Electrochemical systems comprised of unique photonic structures and functions that enable efficient and affordable energy harvesting/conversion/storage are highly desired for providing safe and environment-friendly energy sources. This chapter reviews our recent work of LSPR enabled photoelectrochemical water splitting and recent advances in LSPR-enabled CO2 reduction and photochemical reactions reported in the literature. Scientific and technical challenges of applying LSPR to enhance these energy conversion and storage systems are discussed at the conclusion of this chapter.

Pan, Shanlin↗
DOE OSTI2020

Materials Data on CuAu3 by Materials Project

Au3Cu is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Au+0.33- is bonded to eight equivalent Au+0.33- and four equivalent Cu1+ atoms to form distorted AuCu4Au8 cuboctahedra that share corners with twelve equivalent AuCu4Au8 cuboctahedra, edges with eight equivalent CuAu12 cuboctahedra, edges with sixteen equivalent AuCu4Au8 cuboctahedra, faces with four equivalent CuAu12 cuboctahedra, and faces with fourteen equivalent AuCu4Au8 cuboctahedra. All Au–Au bond lengths are 2.87 Å. All Au–Cu bond lengths are 2.87 Å. Cu1+ is bonded to twelve equivalent Au+0.33- atoms to form CuAu12 cuboctahedra that share corners with twelve equivalent CuAu12 cuboctahedra, edges with twenty-four equivalent AuCu4Au8 cuboctahedra, faces with six equivalent CuAu12 cuboctahedra, and faces with twelve equivalent AuCu4Au8 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cu3Au by Materials Project

Cu3Au is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Au is bonded to twelve equivalent Cu atoms to form AuCu12 cuboctahedra that share corners with twelve equivalent AuCu12 cuboctahedra, edges with twenty-four equivalent CuCu8Au4 cuboctahedra, faces with six equivalent AuCu12 cuboctahedra, and faces with twelve equivalent CuCu8Au4 cuboctahedra. All Au–Cu bond lengths are 2.67 Å. Cu is bonded to four equivalent Au and eight equivalent Cu atoms to form distorted CuCu8Au4 cuboctahedra that share corners with twelve equivalent CuCu8Au4 cuboctahedra, edges with eight equivalent AuCu12 cuboctahedra, edges with sixteen equivalent CuCu8Au4 cuboctahedra, faces with four equivalent AuCu12 cuboctahedra, and faces with fourteen equivalent CuCu8Au4 cuboctahedra. All Cu–Cu bond lengths are 2.67 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CuAu by Materials Project

AuCu is Tetraauricupride structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Au1- is bonded in a distorted body-centered cubic geometry to eight equivalent Cu1+ atoms. All Au–Cu bond lengths are 2.73 Å. Cu1+ is bonded in a body-centered cubic geometry to eight equivalent Au1- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CuAu by Materials Project

AuCu crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are five inequivalent Au1- sites. In the first Au1- site, Au1- is bonded in a 12-coordinate geometry to four Au1- and eight Cu1+ atoms. There are two shorter (2.82 Å) and two longer (2.84 Å) Au–Au bond lengths. There are a spread of Au–Cu bond distances ranging from 2.70–2.86 Å. In the second Au1- site, Au1- is bonded in a distorted body-centered cubic geometry to two equivalent Au1- and eight Cu1+ atoms. There are a spread of Au–Cu bond distances ranging from 2.72–2.80 Å. In the third Au1- site, Au1- is bonded in a distorted body-centered cubic geometry to eight Cu1+ atoms. There are a spread of Au–Cu bond distances ranging from 2.72–2.74 Å. In the fourth Au1- site, Au1- is bonded in a distorted body-centered cubic geometry to eight Cu1+ atoms. There are two shorter (2.72 Å) and six longer (2.73 Å) Au–Cu bond lengths. In the fifth Au1- site, Au1- is bonded in a distorted body-centered cubic geometry to eight Cu1+ atoms. There are two shorter (2.72 Å) and six longer (2.73 Å) Au–Cu bond lengths. There are five inequivalent Cu1+ sites. In the first Cu1+ site, Cu1+ is bonded in a 8-coordinate geometry to eight Au1- atoms. In the second Cu1+ site, Cu1+ is bonded in a body-centered cubic geometry to eight Au1- atoms. In the third Cu1+ site, Cu1+ is bonded in a body-centered cubic geometry to eight Au1- atoms. In the fourth Cu1+ site, Cu1+ is bonded in a body-centered cubic geometry to eight Au1- atoms. In the fifth Cu1+ site, Cu1+ is bonded in a body-centered cubic geometry to eight Au1- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CuAu3 by Materials Project

Au3Cu is Uranium Silicide-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Au+0.33- is bonded to eight equivalent Au+0.33- and four equivalent Cu1+ atoms to form distorted AuCu4Au8 cuboctahedra that share corners with four equivalent CuAu12 cuboctahedra, corners with fourteen equivalent AuCu4Au8 cuboctahedra, edges with six equivalent CuAu12 cuboctahedra, edges with twelve equivalent AuCu4Au8 cuboctahedra, faces with four equivalent CuAu12 cuboctahedra, and faces with sixteen equivalent AuCu4Au8 cuboctahedra. There are a spread of Au–Au bond distances ranging from 2.81–2.91 Å. There are two shorter (2.85 Å) and two longer (2.88 Å) Au–Cu bond lengths. Cu1+ is bonded to twelve equivalent Au+0.33- atoms to form CuAu12 cuboctahedra that share corners with six equivalent CuAu12 cuboctahedra, corners with twelve equivalent AuCu4Au8 cuboctahedra, edges with eighteen equivalent AuCu4Au8 cuboctahedra, faces with eight equivalent CuAu12 cuboctahedra, and faces with twelve equivalent AuCu4Au8 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CuAu4 by Materials Project

Au4Cu crystallizes in the trigonal R-3m space group. The structure is three-dimensional. there are two inequivalent Au+0.25- sites. In the first Au+0.25- site, Au+0.25- is bonded in a 12-coordinate geometry to three equivalent Au+0.25- and three equivalent Cu1+ atoms. All Au–Au bond lengths are 2.97 Å. All Au–Cu bond lengths are 2.68 Å. In the second Au+0.25- site, Au+0.25- is bonded to twelve Au+0.25- atoms to form a mixture of corner, edge, and face-sharing AuAu12 cuboctahedra. There are six shorter (2.93 Å) and three longer (2.95 Å) Au–Au bond lengths. Cu1+ is bonded in a distorted hexagonal planar geometry to six equivalent Au+0.25- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CuAu by Materials Project

AuCu crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Au1- is bonded in a 12-coordinate geometry to six equivalent Cu1+ atoms. All Au–Cu bond lengths are 2.70 Å. Cu1+ is bonded in a distorted hexagonal planar geometry to six equivalent Au1- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cu4Au by Materials Project

AuCu4 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Au is bonded to six equivalent Au and six equivalent Cu atoms to form distorted AuCu6Au6 cuboctahedra that share corners with six equivalent AuCu6Au6 cuboctahedra, corners with six CuCu12 cuboctahedra, edges with six equivalent AuCu6Au6 cuboctahedra, edges with eighteen CuCu9Au3 cuboctahedra, faces with six equivalent AuCu6Au6 cuboctahedra, and faces with twelve equivalent CuCu9Au3 cuboctahedra. All Au–Au bond lengths are 2.71 Å. All Au–Cu bond lengths are 2.77 Å. There are six inequivalent Cu sites. In the first Cu site, Cu is bonded to three equivalent Au and nine Cu atoms to form distorted CuCu9Au3 cuboctahedra that share corners with twelve CuCu9Au3 cuboctahedra, edges with six equivalent AuCu6Au6 cuboctahedra, edges with eighteen CuCu9Au3 cuboctahedra, faces with six equivalent AuCu6Au6 cuboctahedra, and faces with twelve CuCu9Au3 cuboctahedra. There are three shorter (2.53 Å) and six longer (2.71 Å) Cu–Cu bond lengths. In the second Cu site, Cu is bonded to twelve Cu atoms to form CuCu12 cuboctahedra that share corners with three equivalent AuCu6Au6 cuboctahedra, corners with nine CuCu9Au3 cuboctahedra, edges with three equivalent AuCu6Au6 cuboctahedra, edges with twenty-one CuCu9Au3 cuboctahedra, and faces with eighteen CuCu9Au3 cuboctahedra. There are three shorter (2.52 Å) and six longer (2.71 Å) Cu–Cu bond lengths. In the third Cu site, Cu is bonded to twelve Cu atoms to form CuCu12 cuboctahedra that share corners with three equivalent AuCu6Au6 cuboctahedra, corners with nine CuCu9Au3 cuboctahedra, edges with three equivalent AuCu6Au6 cuboctahedra, edges with twenty-one CuCu9Au3 cuboctahedra, and faces with eighteen CuCu9Au3 cuboctahedra. There are three shorter (2.53 Å) and six longer (2.71 Å) Cu–Cu bond lengths. In the fourth Cu site, Cu is bonded to twelve Cu atoms to form CuCu12 cuboctahedra that share corners with three equivalent AuCu6Au6 cuboctahedra, corners with nine CuCu9Au3 cuboctahedra, edges with three equivalent AuCu6Au6 cuboctahedra, edges with twenty-one CuCu9Au3 cuboctahedra, and faces with eighteen CuCu9Au3 cuboctahedra. There are a spread of Cu–Cu bond distances ranging from 2.52–2.71 Å. In the fifth Cu site, Cu is bonded to twelve Cu atoms to form CuCu12 cuboctahedra that share corners with three equivalent AuCu6Au6 cuboctahedra, corners with nine CuCu9Au3 cuboctahedra, edges with three equivalent AuCu6Au6 cuboctahedra, edges with twenty-one CuCu9Au3 cuboctahedra, and faces with eighteen CuCu9Au3 cuboctahedra. There are three shorter (2.53 Å) and six longer (2.71 Å) Cu–Cu bond lengths. In the sixth Cu site, Cu is bonded to twelve Cu atoms to form CuCu12 cuboctahedra that share corners with three equivalent AuCu6Au6 cuboctahedra, corners with nine CuCu9Au3 cuboctahedra, edges with three equivalent AuCu6Au6 cuboctahedra, edges with twenty-one CuCu9Au3 cuboctahedra, and faces with eighteen CuCu9Au3 cuboctahedra. There are a spread of Cu–Cu bond distances ranging from 2.52–2.71 Å.

36 MATERIALS SCIENCE↗