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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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All sourcesNASA NTRSDOE OSTI
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.↗
NASA NTRS1975

Development of gold alloy catalyst cathode for alkaline electrolyte fuel cells

A program for the development of improved catalyst and Teflon-bonded electrode structures using this improved catalyst is described, for use in fuel cell cathodes. It was found that Au-Pt was superior to the traditional platinum black as a catalyst. The impetus to the program was provided by the discovery that a life-limiting mechanism on the old catalyst was the gradual dissolution of platinum from the cathode and subsequent redeposition in the electrolyte-containing matrix.

Freed, M. S.↗
DOE OSTI2020

Synthesis and Characterization of Pd-based Nanomaterials

Bimetallic nanoparticles (BNPs) consist of two different types of metals or alloys that are bonded together. Unique properties such as optical, electronic, thermal, and catalytic effects differ for each type of BNP. Important BNPs range from Au-Pd, Ag- Pt, Au-Pt, and Ag-Ni. Pd bimetallic nanoparticles are of interest due to their many applications such as catalysis and sensing. Bimetallic catalysts have increase reaction rates and have improved catalyst stability through the geometry and ligand distribution. Pd nanoparticles are considered to be a strong catalyst due to their high activity at low temperatures and high tolerance to moisture. The catalytic properties of bimetallic nanoparticles depend on the structural properties such as size and shape. Core-shell, hollow structure, and multi-shell alloy are three possible structures nanoparticles can form as bimetallic catalysts. BNPs can be synthesized through different methods to control the size, shape, and structure. To obtain different morphologies, a variety of methods can be performed. Different methods can range from the usage of the glancing angle deposition (GLAD) to the galvanic replacement reaction, but the methods all depend on the properties of the metals. The galvanic displacement reaction was the method used to obtain Pd-based nanoparticles. This reaction is best know for obtaining hollow shaped NPs. To determine what redox process was preformed, the activity series of metals was used. From the activity series of metals, silver (Ag) was selected to preform Pd-based nanoparticles. Objectives: Synthesize Ag nanoparticles and Ag-Pd nanoparticles to understand the morphology. Characterize the synthesized nanoparticles using scanning electron microscopy (SEM), phase analysis light scattering (PALS), dynamic light scattering (DLS), energy dispersive X-ray spectroscopy (EDS), and UV-Vis spectroscopy. Results: In the UV-Vis spectrum, the Ag-Pd bimetallic NP's plasmon band decreased as the volume of palladium increased. The surface charge increases as the concentration of palladium increases. The Pd{sup 2+} ions interact with the sodium citrate surface, and decrease the negative charge. Conclusion: Ag-Pd nanoparticles were successfully created and stabilized with sodium citrate. The addition of Pd decreased the prominent plasmon band of the Ag nanoparticles. The SEM analysis showed that Ag nanoparticles had a well-defined structure, while the Ag-Pd nanoparticles showed hollow and rough structure. The EDX analysis confirmed the presence of silver and palladium. This material can be used in many industrial and research fields such as organic synthesis, fuel cells, and environmental sensing and remediation.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Materials Data on PtAu by Materials Project

PtAu crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Pt2- is bonded to six equivalent Pt2- and six equivalent Au2+ atoms to form PtPt6Au6 cuboctahedra that share corners with twelve equivalent AuPt6 cuboctahedra, corners with eighteen equivalent PtPt6Au6 cuboctahedra, edges with six equivalent PtPt6Au6 cuboctahedra, edges with twelve equivalent AuPt6 cuboctahedra, and faces with eight equivalent PtPt6Au6 cuboctahedra. All Pt–Pt bond lengths are 2.85 Å. All Pt–Au bond lengths are 2.91 Å. Au2+ is bonded to six equivalent Pt2- atoms to form distorted AuPt6 cuboctahedra that share corners with twelve equivalent PtPt6Au6 cuboctahedra, corners with twelve equivalent AuPt6 cuboctahedra, edges with six equivalent AuPt6 cuboctahedra, edges with twelve equivalent PtPt6Au6 cuboctahedra, and faces with two equivalent AuPt6 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PtAu by Materials Project

PtAu crystallizes in the trigonal R-3m space group. The structure is three-dimensional. there are two inequivalent Pt2- sites. In the first Pt2- site, Pt2- is bonded to six equivalent Pt2- and six Au2+ atoms to form a mixture of face, edge, and corner-sharing PtPt6Au6 cuboctahedra. All Pt–Pt bond lengths are 2.87 Å. All Pt–Au bond lengths are 2.88 Å. In the second Pt2- site, Pt2- is bonded to ten equivalent Pt2- and six Au2+ atoms to form PtPt10Au6 cuboctahedra that share corners with twelve PtPt6Au6 cuboctahedra, edges with sixteen PtPt6Au6 cuboctahedra, and faces with sixteen equivalent PtPt10Au6 cuboctahedra. There are a spread of Pt–Pt bond distances ranging from 2.87–5.74 Å. All Pt–Au bond lengths are 2.88 Å. There are three inequivalent Au2+ sites. In the first Au2+ site, Au2+ is bonded in a 6-coordinate geometry to six equivalent Pt2- atoms. In the second Au2+ site, Au2+ is bonded in a 6-coordinate geometry to six Pt2- atoms. All Au–Pt bond lengths are 2.88 Å. In the third Au2+ site, Au2+ is bonded in a 6-coordinate geometry to six Pt2- atoms.

36 MATERIALS SCIENCE↗