Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Ag(NO)3”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Interstitial Atoms and the Frustrated and Allowed Structural Transitions Principle: Tunability in the Electronic Structure of AuCu 3 ‐type Frameworks in Dy 4 T 1− x Ga 12 (T = Ag, Ir)

In this Article, we explore how the chemical pressure (CP) features of an intermetallic phase may provide opportunities to couple perturbations in electron count with the stabilization of the underlying geometrical structure. AuCu 3 ‐type LnGa 3 (Ln = lanthanide or group 3 metal) phases contain octahedral cavities of negative CP held open by overly compressed Ln–Ga interactions, leading to a series of transition metal‐stuffed derivatives. We present new additions to this family with the synthesis and crystal structures of Dy 4 T 1−x Ga 12 with (T, x) = (Ag, 0.29) and (Ir, 0.15), adopting Y 4 PdGa 12 ‐type superstructures of the AuCu 3 ‐type. density functional Ttheory (DFT)‐CP calculations, when adjusted to avoid dipolar CP features, affirm that T atom incorporation provides a mechanism for the relief of packing tensions, while electronic density of states distributions illustrate that the T atoms serve largely as electron or hole donors to the band structure, as needed for them to attain d 10 configurations. The maximum obtainable value for x may be limited by a mismatch between the Fermi energy and pseudogap, in line with the balance of factors envisioned by the frustrated and allowed structural transitions principle. Furthermore, trends in resistivity measurements on T = Ir, Pd, and Ag compounds are interpretable in terms of the varying degrees of disorder arising from x < 1.0.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Cubic AgMnSbTe 3 Semiconductor with a High Thermoelectric Performance

The reaction of MnTe with AgSbTe 2 in an equimolar ratio (ATMS) provides a new semiconductor, AgMnSbTe 3 . AgMnSbTe 3 crystallizes in an average rock-salt NaCl structure with Ag, Mn, and Sb cations statistically occupying the Na sites. AgMnSbTe 3 is a p-type semiconductor with a narrow band gap of ~0.33 eV. A pair distribution function analysis indicates that local distortions are associated with the location of the Ag atoms in the lattice. Density functional theory calculations suggest a specific electronic band structure with multi-peak valence band maxima prone to energy convergence. In addition, Ag 2 Te nanograins precipitate at grain boundaries of AgMnSbTe 3 . Here, the energy offset of the valance band edge between AgMnSbTe 3 and Ag 2 Te is ~0.05 eV, which implies that Ag 2 Te precipitates exhibit a negligible effect on the hole transmission. As a result, ATMS exhibits a high power factor of ~12.2 μWcm -1 K -2 at 823 K, ultralow lattice thermal conductivity of ~0.34 Wm -1 K -1 (823 K), high peak ZT of ~1.46 at 823 K, and high average ZT of ~0.87 in the temperature range of 400–823 K.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Toward white light emission from plasmonic-luminescent hybrid nanostructures

We study the light emission of plasmonic-luminescent hybrid nanostructures consisting of Ag nanoparticles (NPs) embedded in europium oxide (EuO X ). The Ag NPs present a bidimensional organization in the nanostructures and they optically behave as oblate spheroids. The photoluminescence (PL) spectral response of the nanostructures evolves from a narrow red emission characteristic of Eu 3+ ions in absence of Ag NPs to a broad blue-green emission band associated with Eu 2+ ions when the layer of Ag NPs is present. This behavior is not related to a change in the Eu 2+ /Eu 3+ ratio, which is verified by compositional analysis. Instead, a detailed investigation of the PL emission of the nanostructures suggests that the coupling of the Ag NPs to the Eu 2+ ions present in the EuO X layer, which manifests itself in an efficient sensitization of these ions, enhances their broad visible emission. In particular, the longitudinal mode of the Ag NPs surface plasmon is considered to be responsible for the efficient energy transfer for the non-normal incidence excitation PL configuration used. Finally, the use of a capping amorphous Al 2 O 3 layer allows improving the robustness of hybrid nanostructures and further enhances their PL emission. These findings provide a new path to actively control the selective excitation of Eu 2+ and Eu 3+ ions via a controlled coupling with the surface plasmon resonance modes of the Ag NPs and points to these nanostructures as promising building blocks for the development of integrable white light sources.

36 MATERIALS SCIENCE↗
DOE OSTI2022

High-performance and stable AgSbTe 2 -based thermoelectric materials for near room temperature applications

AgSbTe 2 -based ternary chalcogenides show excellent thermoelectric performance at low- and middle-temperature ranges, yet their practical applications are greatly limited by their intrinsic poor thermodynamic stability. In this work, we demonstrate that AgSbTe 2 -based ternary chalcogenides can be stabilized for service below their decomposition threshold. A series of Ag x Sb 2-x Te 3-x (x = 1.0, 0.9, 0.8 and 0.7) samples have been prepared by the melt-quenching method. Among them, phase pure Ag 0.9 Sb 1.1 Te 2.1 is verified by comprehensive structural characterizations from macroscale by X-ray diffraction to microscale by energy-dispersive spectroscopy and then to sub-nanometer scale by atom probe tomography. This composition is further chosen for the stability investigation. The decomposition threshold of Ag 0.9 Sb 1.1 Te 2.1 appears around 473K. Below this temperature, the chemical compositions and thermoelectric properties are barely changed even after 720 h annealing at 473 K. The figure-of-merit (zT) value of Ag 0.9 Sb 1.1 Te 2.1 below the decomposition threshold is very competitive for real applications even compared with Bi 2 Te 3 -based alloys. The average zT of Ag 0.9 Sb 1.1 Te 2.1 at 300–473 K reaches 0.84, which is higher than most other thermoelectric materials in a similar temperature range, promising applications in miniaturized refrigeration and power generation near room temperature.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Surface Reactivity of Ag-Modified Ceria to Hydrogen: A Combined Experimental and Theoretical Investigation

We investigate the mechanism of H 2 activation on Ag-modified cerium oxide surfaces, of interest for different catalytic applications. The study is performed on thin epitaxial cerium oxide films, investigated by X-ray photoemission spectroscopy to assess the changes of both the Ag oxidation state and the concentration of Ce 3+ ions, O vacancies, and hydroxyl groups on the surface during thermal reduction cycles in vacuum and under hydrogen exposure. The results are interpreted using density functional theory calculations to model pristine and Ag-modified ceria surfaces. Although the reactivity of ceria toward H 2 oxidation improves when a fraction of Ce cations is substituted with Ag, the concentration of reduced Ce 3+ ions in Ag-modified ceria is found to be lower than in pure ceria under the same conditions. This behavior is observed even though the number of surface oxygen vacancies caused by the thermal treatment under hydrogen exposure is larger for the Ag-modified surface. These results are explained in terms of a change of the oxidation state of the surface Ag, which is able to acquire some of the extra surface electrons created by the oxygen vacancies and the adsorbed hydrogen atoms. Our findings provide new insights into the reactivity of Ag-modified ceria, which has been proposed as a promising alternative to platinum electrodes in electrochemical devices.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on Na7Al11Si13(AgO12)4 by Materials Project

Na7Al11Si13(AgO12)4 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are seven inequivalent Na sites. In the first Na site, Na is bonded in a 3-coordinate geometry to three O atoms. There are a spread of Na–O bond distances ranging from 2.17–2.65 Å. In the second Na site, Na is bonded in a distorted L-shaped geometry to two O atoms. There are one shorter (2.13 Å) and one longer (2.30 Å) Na–O bond lengths. In the third Na site, Na is bonded in a distorted L-shaped geometry to two O atoms. There are one shorter (2.12 Å) and one longer (2.33 Å) Na–O bond lengths. In the fourth Na site, Na is bonded in a distorted L-shaped geometry to two O atoms. There are one shorter (2.34 Å) and one longer (2.45 Å) Na–O bond lengths. In the fifth Na site, Na is bonded in a 1-coordinate geometry to four O atoms. There are a spread of Na–O bond distances ranging from 2.23–2.87 Å. In the sixth Na site, Na is bonded in a distorted trigonal non-coplanar geometry to three O atoms. There are a spread of Na–O bond distances ranging from 2.26–2.34 Å. In the seventh Na site, Na is bonded in a 5-coordinate geometry to five O atoms. There are a spread of Na–O bond distances ranging from 2.36–2.78 Å. There are four inequivalent Ag sites. In the first Ag site, Ag is bonded in a trigonal planar geometry to three O atoms. There are a spread of Ag–O bond distances ranging from 2.17–2.47 Å. In the second Ag site, Ag is bonded in a 3-coordinate geometry to three O atoms. There are a spread of Ag–O bond distances ranging from 2.23–2.55 Å. In the third Ag site, Ag is bonded in a distorted trigonal non-coplanar geometry to three O atoms. There are a spread of Ag–O bond distances ranging from 2.27–2.36 Å. In the fourth Ag site, Ag is bonded in a 2-coordinate geometry to two O atoms. There are one shorter (2.29 Å) and one longer (2.38 Å) Ag–O bond lengths. There are eleven inequivalent Al sites. In the first Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share corners with two AlO4 tetrahedra and corners with two SiO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.71–1.79 Å. In the second Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share a cornercorner with one SiO4 tetrahedra and corners with three AlO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.70–1.83 Å. In the third Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share corners with two AlO4 tetrahedra and corners with two SiO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.75–1.77 Å. In the fourth Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share a cornercorner with one SiO4 tetrahedra and corners with three AlO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.75–1.77 Å. In the fifth Al site, Al is bonded to four O atoms to form corner-sharing AlO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.72–1.80 Å. In the sixth Al site, Al is bonded to four O atoms to form corner-sharing AlO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.73–1.78 Å. In the seventh Al site, Al is bonded to four O atoms to form distorted corner-sharing AlO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.72–1.78 Å. In the eighth Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share corners with two AlO4 tetrahedra and corners with two SiO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.71–1.81 Å. In the ninth Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share corners with two AlO4 tetrahedra and corners with two SiO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.71–1.81 Å. In the tenth Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share corners with two AlO4 tetrahedra and corners with two SiO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.67–1.85 Å. In the eleventh Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share corners with two AlO4 tetrahedra and corners with two SiO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.69–1.79 Å. There are thirteen inequivalent Si sites. In the first Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.62–1.65 Å. In the second Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There is two shorter (1.64 Å) and two longer (1.65 Å) Si–O bond length. In the third Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.63–1.65 Å. In the fourth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.63–1.65 Å. In the fifth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.63–1.66 Å. In the sixth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There is two shorter (1.63 Å) and two longer (1.65 Å) Si–O bond length. In the seventh Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.62–1.66 Å. In the eighth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.62–1.66 Å. In the ninth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.60–1.68 Å. In the tenth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.57–1.68 Å. In the eleventh Si site, Si is bonded to four O atoms to form corner-sharing SiO4 tetrahedra. There is one shorter (1.62 Å) and three longer (1.64 Å) Si–O bond length. In the twelfth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.57–1.65 Å. In the thirteenth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one SiO4 tetrahedra and corners with three AlO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.59–1.69 Å. There are forty-eight inequivalent O sites. In the first O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the second O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the third O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the fourth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the fifth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the sixth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the seventh O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the eighth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the ninth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the tenth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the eleventh O site, O is bonded in a distorted bent 150 degrees geometry to one Ag and two Si atoms. In the twelfth O site, O is bonded in a distorted bent 150 degrees geometry to one Ag and two Si atoms. In the thirteenth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the fourteenth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the fifteenth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the sixteenth O site, O is bonded in a distorted bent 150 degrees geometry to one Na and two Si atoms. In the seventeenth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the eighteenth O site, O is bonded in a 2-coordinate geometry to one Na, one Al, and one Si atom. In the nineteenth O site, O is bonded in a linear geometry to one Al and one Si atom. In the twentieth O site, O is bonded in a bent 150 degrees geometry to one Al and one Si atom. In the twenty-first O site, O is bonded in a bent 150 degrees geometry to one Al and one Si atom. In the twenty-second O site, O is bonded in a bent 120 degrees geometry to two Al atoms. In the twenty-third O site, O is bonded in a bent 150 degrees geometry to one Al and one Si atom. In the twenty-fourth O site, O is bonded in a 2-coordinate geometry to one Ag and two Al atoms. In the twenty-fifth O site, O is bonded in a 2-coordinate geometry to one Na and two Al atoms. In the twenty-sixth O site, O is bonded in a 3-coordinate geometry to one Na and two Al atoms. In the twenty-seventh O site, O is bonded in a 3-coordinate geometry to one Na, one Al, and one Si atom. In the twenty-eighth O site, O is bonded in a distorted bent 120 degrees geometry to one Na and two Al atoms. In the twenty-ninth O site, O is bonded in a 3-coordinate geometry to one Ag and two Al atoms. In the thirtieth O site, O is bonded in a 4-coordinate geometry to one Na, one Ag, and two Al atoms. In the thirty-first O site, O is bonded in a distorted trigonal pyramidal geometry to one Na, one Ag, and two Al atoms. In the thirty-second O site, O is bonded in a distorted rectangular see-saw-like geometry to one Na, one Ag, and two Al atoms. In the thirty-third O site, O is bonded in a 2-coordinate geometry to one Na and two Al atoms. In the thirty-fourth O site, O is bonded in a 2-coordinate geometry to one Na and two Al atoms. In the thirty-fifth O site, O is bonded in a 3-coordinate geometry to two Na and two Al atoms. In the thirty-sixth O site, O is bonded in a 4-coordinate geometry to two Na and two Al atoms. In the thirty-seventh O site, O is bonded in a bent 150 degrees geometry to two Al atoms. In the thirty-eighth O site, O is bonded in a distorted T-shaped geometry to one Na and two Al atoms. In the thirty-ninth O site, O is bonded in a 2-coordinate geometry to one Ag, one Al, and one Si atom. In the fortieth O site, O is bonded in a distorted bent 150 degrees geometry to one Ag, one Al, and one Si atom. In the forty-first O site, O is bonded in a 2-coordinate geometry to one Ag, one Al, and one Si atom. In the forty-second O site, O is bonded in a distorted trigonal planar geometry to one Na, one Al, and one Si atom. In the forty-third O site, O is bonded in a 4-coordinate geometry to one Na, one Ag, one Al, and one Si atom. In the forty-fourth O site, O is bonded in a distorted trigonal planar geometry to one Na, one Al, and one Si atom. In the forty-fifth O site, O is bonded in a 3-coordinate geometry to one Na, one Al, and one Si atom. In the forty-sixth O site, O is bonded in a 3-coordinate geometry to one Na, one Al, and one Si atom. In the forty-seventh O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the forty-eighth O site, O is bonded in a bent 150 degrees geometry to two Si atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

A comparative study of silver- and palladium-exchanged zeolites in propylene and nitrogen oxide adsorption and desorption for cold-start applications

Here, silver and palladium ion-exchanged BEA zeolites (Si/Al = 12.5) and silver ion-exchanged ZSM-5 zeolites (Si/Al = 15) were studied for their ability to adsorb and desorb propylene and NO under simulated diesel exhaust conditions. The adsorption experiment results demonstrated the excellent ability of bare BEA zeolites to adsorb propylene, but only a small amount of NO. The presence of H 2 O inhibited the adsorption of both C 3 H 6 and NO. Ion-exchanging BEA zeolites with Ag (1.2 and 5.1 wt.% Ag/BEA) attenuated the inhibiting effect of H 2 O on C 3 H 6 adsorption, while NO storage remained inhibited. Adsorption experiments indicated that C 3 H 6 and NO competed with each other for Pd sites with C 3 H 6 showing stronger adsorption compared to NO, whereas Ag sites preferentially adsorbed C 3 H 6 . DRIFTS data indicated the formation of nitrate, formate and acetate species on Ag and Pd, while C 3 H 6 and NO adsorption was also observed on the zeolite hydroxyl groups in the absence of H 2 O. However, the C 3 H 6 and NO adsorption on the zeolite hydroxyl groups was significantly inhibited in the presence of H 2 O. Additionally, nitrosyl, acrolein and carbonate species were formed over 1.0 wt.% Pd/BEA. The effluent analysis during the temperature-programmed desorption in the DRIFTS reactor revealed that adsorbed C 3 H 6 and NO reacted during the release to form oxidation reaction byproducts. The 1.0 wt.% Pd/BEA zeolite showed the greatest oxidation ability during desorption with the majority of stored C 3 H 6 converted to CO 2 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Evaluation of Getter Metals in Na–Al–Si–O Aerogels and Xerogels for the Capture of Iodine Gas

In this paper, sodium aluminosilicate aerogels and xerogels were evaluated as scaffolds for a variety of different getters including: Ag + , Cs + , Cu 2+ , Fe 3+ , K + , Li + , Rb + , Sb 3+ , Sn 2+ , and Sn 4+ . The exchange capacities varied widely from a near complete exchange in the case of Ag + to much lower exchange levels for some of the Sn compounds [i.e., colloidal SnO 2 , Sn(II) acetate, Sn(IV) acetate]. Several of the additives showed great promise at allowing for high iodine loadings in the base materials including the following: AgNO 3 , colloidal SnO 2 , Sn(II) acetate, Sn(IV) acetate, Cu(NO 3 ) 2 , and CuSO 4 . From the standpoint of iodine uptake as a function of getter loading, the Sn4+ showed the most promise with a getter utilization (mass of iodine divided by mass of Sn, in atomic%) of 8.4, a chemical uptake of 60.7 mass% (oxygen excluded), and an mI $m_s^{-1}$ value of 0.881; these are some of the highest values reported to date for inorganic iodine sorbents.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on LiAg2F4 by Materials Project

LiAg2F4 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Li1+ is bonded to four F1- atoms to form LiF4 tetrahedra that share corners with five equivalent AgF5 trigonal bipyramids. There are a spread of Li–F bond distances ranging from 1.88–1.95 Å. There are two inequivalent Ag+1.50+ sites. In the first Ag+1.50+ site, Ag+1.50+ is bonded in a 4-coordinate geometry to five F1- atoms. There are a spread of Ag–F bond distances ranging from 2.26–2.85 Å. In the second Ag+1.50+ site, Ag+1.50+ is bonded to five F1- atoms to form distorted AgF5 trigonal bipyramids that share corners with five equivalent LiF4 tetrahedra and an edgeedge with one AgF5 trigonal bipyramid. There are a spread of Ag–F bond distances ranging from 2.18–2.56 Å. There are four inequivalent F1- sites. In the first F1- site, F1- is bonded in a 4-coordinate geometry to one Li1+ and three Ag+1.50+ atoms. In the second F1- site, F1- is bonded in a 3-coordinate geometry to one Li1+ and two Ag+1.50+ atoms. In the third F1- site, F1- is bonded in a 1-coordinate geometry to one Li1+ and three Ag+1.50+ atoms. In the fourth F1- site, F1- is bonded in a 3-coordinate geometry to one Li1+ and two Ag+1.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Synthesis and Characterization of Pt‐Ag Icosahedral Nanocages with Enhanced Catalytic Activity toward Oxygen Reduction

Abstract There is an urgent need to develop cost‐effective electrocatalysts based on Pt for a broad spectrum of applications, including those vital to the operation of fuel cells. Hollowing out the interior of Pt nanocrystals offers a simple and viable strategy for maximizing the utilization efficiency of this precious metal while enhancing the electrocatalytic performance. Herein, we report the synthesis and electrocatalytic evaluation of Pt−Ag icosahedral nanocages with an average wall thickness of 1.6 nm. The Pt atoms are coated on the surface of Ag icosahedral seeds, leading to the formation of Ag@Pt nL core‐shell icosahedral nanocrystals with tunable shell thicknesses. The core‐shell nanocrystals are then converted to icosahedral nanocages by selectively etching away the Ag in the core. The as‐obtained nanocages with a composition of Pt 4.5 Ag exhibit an almost 3‐fold enhancement in specific activity toward oxygen reduction relative to the commercial Pt/C in acid media.

Wang, Wenxia↗
DOE OSTI2021

Robust method for broadband efficiency enhancement of electron photocathodes using optical interferences

In this work, we demonstrate the key features of an interference cathode using both simulations and experiments. We deposit Cs 3 Sb photocathodes on Ag to produce an interference enhanced photocathode with 2–5× quantum efficiency (QE) enhancement using a robust procedure that requires only a smooth metal substrate and QE monitoring during growth. We grow both an interference cathode (Ag substrate) and a typical photocathode (Si reference substrate) simultaneously to confirm that the effects are due to optical interactions with the substrate rather than photocathode composition or surface electron affinity differences. Growing the cathodes until the QE converges shows both the characteristic interference peaks during growth and the identical limiting case where the cathode is “infinitely thick,” in agreement with simulations. We also grow a cathode until the QE on Ag peaks and then stop the growth, demonstrating broadband QE enhancement.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba2Ag8S7 by Materials Project

Ba2Ag8S7 crystallizes in the orthorhombic Pmn2_1 space group. The structure is three-dimensional. Ba2+ is bonded in a 8-coordinate geometry to eight S2- atoms. There are a spread of Ba–S bond distances ranging from 3.20–3.39 Å. There are five inequivalent Ag+1.25+ sites. In the first Ag+1.25+ site, Ag+1.25+ is bonded in a distorted trigonal planar geometry to three S2- atoms. There are a spread of Ag–S bond distances ranging from 2.55–2.63 Å. In the second Ag+1.25+ site, Ag+1.25+ is bonded in a 3-coordinate geometry to four S2- atoms. There are a spread of Ag–S bond distances ranging from 2.58–3.21 Å. In the third Ag+1.25+ site, Ag+1.25+ is bonded in a 4-coordinate geometry to four S2- atoms. There are a spread of Ag–S bond distances ranging from 2.45–3.24 Å. In the fourth Ag+1.25+ site, Ag+1.25+ is bonded in a 2-coordinate geometry to four S2- atoms. There are a spread of Ag–S bond distances ranging from 2.45–3.34 Å. In the fifth Ag+1.25+ site, Ag+1.25+ is bonded in a 4-coordinate geometry to four S2- atoms. There are a spread of Ag–S bond distances ranging from 2.49–3.35 Å. There are five inequivalent S2- sites. In the first S2- site, S2- is bonded in a 6-coordinate geometry to six Ag+1.25+ atoms. In the second S2- site, S2- is bonded in a 7-coordinate geometry to one Ba2+ and six Ag+1.25+ atoms. In the third S2- site, S2- is bonded in a 7-coordinate geometry to four equivalent Ba2+, two equivalent Ag+1.25+, and one S2- atom. The S–S bond length is 2.16 Å. In the fourth S2- site, S2- is bonded in a 9-coordinate geometry to four equivalent Ba2+, four Ag+1.25+, and one S2- atom. In the fifth S2- site, S2- is bonded in a 6-coordinate geometry to three equivalent Ba2+ and three Ag+1.25+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na8Al11Si13(AgO16)3 by Materials Project

Na8Al11Si13(AgO16)3 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are eight inequivalent Na sites. In the first Na site, Na is bonded in a 5-coordinate geometry to five O atoms. There are a spread of Na–O bond distances ranging from 2.34–2.82 Å. In the second Na site, Na is bonded in a 1-coordinate geometry to three O atoms. There are a spread of Na–O bond distances ranging from 2.29–2.71 Å. In the third Na site, Na is bonded in a 2-coordinate geometry to two O atoms. There are one shorter (2.16 Å) and one longer (2.20 Å) Na–O bond lengths. In the fourth Na site, Na is bonded in a 3-coordinate geometry to three O atoms. There are a spread of Na–O bond distances ranging from 2.16–2.45 Å. In the fifth Na site, Na is bonded in a 5-coordinate geometry to five O atoms. There are a spread of Na–O bond distances ranging from 2.23–2.93 Å. In the sixth Na site, Na is bonded in a 5-coordinate geometry to four O atoms. There are a spread of Na–O bond distances ranging from 2.21–2.81 Å. In the seventh Na site, Na is bonded in a 5-coordinate geometry to five O atoms. There are a spread of Na–O bond distances ranging from 2.22–2.90 Å. In the eighth Na site, Na is bonded in a distorted pentagonal planar geometry to five O atoms. There are a spread of Na–O bond distances ranging from 2.27–2.75 Å. There are three inequivalent Ag sites. In the first Ag site, Ag is bonded in a distorted trigonal planar geometry to three O atoms. There are a spread of Ag–O bond distances ranging from 2.20–2.43 Å. In the second Ag site, Ag is bonded in a 3-coordinate geometry to four O atoms. There are a spread of Ag–O bond distances ranging from 2.30–2.72 Å. In the third Ag site, Ag is bonded in a 4-coordinate geometry to four O atoms. There are a spread of Ag–O bond distances ranging from 2.29–2.55 Å. There are eleven inequivalent Al sites. In the first Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share corners with four SiO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.74–1.78 Å. In the second Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share corners with two AlO4 tetrahedra and corners with two SiO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.72–1.82 Å. In the third Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share corners with two AlO4 tetrahedra and corners with two SiO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.73–1.81 Å. In the fourth Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share a cornercorner with one SiO4 tetrahedra and corners with three AlO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.73–1.79 Å. In the fifth Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share a cornercorner with one SiO4 tetrahedra and corners with three AlO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.71–1.83 Å. In the sixth Al site, Al is bonded to four O atoms to form corner-sharing AlO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.72–1.76 Å. In the seventh Al site, Al is bonded to four O atoms to form corner-sharing AlO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.71–1.80 Å. In the eighth Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share corners with two AlO4 tetrahedra and corners with two SiO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.69–1.82 Å. In the ninth Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share corners with two AlO4 tetrahedra and corners with two SiO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.68–1.80 Å. In the tenth Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share corners with two AlO4 tetrahedra and corners with two SiO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.73–1.80 Å. In the eleventh Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share corners with two AlO4 tetrahedra and corners with two SiO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.72–1.80 Å. There are thirteen inequivalent Si sites. In the first Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.61–1.68 Å. In the second Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with two AlO4 tetrahedra and corners with two SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.62–1.65 Å. In the third Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. In the fourth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. In the fifth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with two AlO4 tetrahedra and corners with two SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.62–1.65 Å. In the sixth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.61–1.69 Å. In the seventh Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. In the eighth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.61–1.68 Å. In the ninth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.59–1.67 Å. In the tenth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with two AlO4 tetrahedra and corners with two SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.60–1.67 Å. In the eleventh Si site, Si is bonded to four O atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.60–1.66 Å. In the twelfth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with two AlO4 tetrahedra and corners with two SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.58–1.67 Å. In the thirteenth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one SiO4 tetrahedra and corners with three AlO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.62–1.67 Å. There are forty-eight inequivalent O sites. In the first O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the second O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the third O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the fourth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the fifth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the sixth O site, O is bonded in a distorted bent 150 degrees geometry to one Ag and two Si atoms. In the seventh O site, O is bonded in a distorted bent 150 degrees geometry to one Ag and two Si atoms. In the eighth O site, O is bonded in a distorted bent 150 degrees geometry to one Ag and two Si atoms. In the ninth O site, O is bonded in a distorted bent 150 degrees geometry to one Ag and two Si atoms. In the tenth O site, O is bonded in a distorted bent 150 degrees geometry to one Na and two Si atoms. In the eleventh O site, O is bonded in a distorted bent 150 degrees geometry to one Na, one Al, and one Si atom. In the twelfth O site, O is bonded in a 2-coordinate geometry to one Ag, one Al, and one Si atom. In the thirteenth O site, O is bonded in a distorted bent 150 degrees geometry to one Ag and two Si atoms. In the fourteenth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the fifteenth O site, O is bonded in a bent 150 degrees geometry to one Al and one Si atom. In the sixteenth O site, O is bonded in a linear geometry to one Na and two Si atoms. In the seventeenth O site, O is bonded in a distorted linear geometry to one Na, one Al, and one Si atom. In the eighteenth O site, O is bonded in a distorted linear geometry to one Ag, one Al, and one Si atom. In the nineteenth O site, O is bonded in a distorted linear geometry to one Ag, one Al, and one Si atom. In the twentieth O site, O is bonded in a distorted bent 150 degrees geometry to one Na and two Si atoms. In the twenty-first O site, O is bonded in a distorted bent 150 degrees geometry to one Ag, one Al, and one Si atom. In the twenty-second O site, O is bonded in a distorted bent 150 degrees geometry to one Ag, one Al, and one Si atom. In the twenty-third O site, O is bonded in a distorted bent 150 degrees geometry to one Ag and two Al atoms. In the twenty-fourth O site, O is bonded in a 3-coordinate geometry to one Na, one Al, and one Si atom. In the twenty-fifth O site, O is bonded in a distorted bent 120 degrees geometry to one Na and two Al atoms. In the twenty-sixth O site, O is bonded in a distorted bent 150 degrees geometry to one Al and one Si atom. In the twenty-seventh O site, O is bonded in a distorted bent 120 degrees geometry to one Na and two Al atoms. In the twenty-eighth O site, O is bonded in a 3-coordinate geometry to one Na and two Al atoms. In the twenty-ninth O site, O is bonded in a 3-coordinate geometry to one Na and two Al atoms. In the thirtieth O site, O is bonded in a 2-coordinate geometry to one Na and two Al atoms. In the thirty-first O site, O is bonded in a 2-coordinate geometry to one Na and two Al atoms. In the thirty-second O site, O is bonded in a bent 150 degrees geometry to one Na and two Al atoms. In the thirty-third O site, O is bonded in a 5-coordinate geometry to three Na and two Al atoms. In the thirty-fourth O site, O is bonded in a distorted trigonal bipyramidal geometry to three Na and two Al atoms. In the thirty-fifth O site, O is bonded in a 2-coordinate geometry to three Na and two Al atoms. In the thirty-sixth O site, O is bonded in a distorted linear geometry to one Na and two Al atoms. In the thirty-seventh O site, O is bonded in a distorted bent 120 degrees geometry to one Na and two Al atoms. In the thirty-eighth O site, O is bonded in a distorted trigonal planar geometry to one Na, one Al, and one Si atom. In the thirty-ninth O site, O is bonded in a 2-coordinate geometry to one Na, one Al, and one Si atom. In the fortieth O site, O is bonded in a distorted bent 150 degrees geometry to one Na, one Al, and one Si atom. In the forty-first O site, O is bonded in a 3-coordinate geometry to one Na, one Al, and one Si atom. In the forty-second O site, O is bonded in a 3-coordinate geometry to one Na, one Al, and one Si atom. In the forty-third O site, O is bonded in a distorted bent 150 degrees geometry to one Na, one Al, and one Si atom. In the forty-fourth O site, O is bonded in a distorted bent 150 degrees geometry to one Na, one Al, and one Si atom. In the forty-fifth O site, O is bonded in a 3-coordinate geometry to one Na, one Al, and one Si atom. In the forty-sixth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the forty-seventh O site, O is bonded in a bent 150 degrees geometry to two Si ato

36 MATERIALS SCIENCE↗
DOE OSTI2021

High Thermoelectric Performance through Crystal Symmetry Enhancement in Triply Doped Diamondoid Compound Cu 2 SnSe 3

The presence of high crystallographic symmetry and nanoscale defects are favorable for thermoelectrics. With proper electronic structures, a highly symmetric crystal tends to possess multiple carrier channels and promote electrical conductivity without sacrificing Seebeck coefficient. In addition, nanoscale defects can effectively scatter acoustic phonons to suppress thermal conductivity. Here, we report that the triple doping of Cu 2 SnSe 3 leads to a high ZT value of 1.6 at 823 K for Cu 1.85 Ag 0.15 (Sn 0.88 Ga 0.1 Na 0.02 )Se 3 , and a decent average ZT (ZT ave ) value of 0.7 is also achieved for Cu 1.85 Ag 0.15 (Sn 0.93 Mg 0.06 Na 0.01 )Se 3 from 475 to 823 K. Our study reveals: (1) Ag doping on Cu sites generates numerous point defects and greatly decreases lattice thermal conductivity. (2) Doping Mg or Ga converts the monoclinic Cu 2 SnSe 3 into a cubic structure. This symmetry enhancing leads to increase in the effective mass from 0.8 m e to 2.6 m e (m e , free electron mass) and the power factor from 4.3 μW/cm –1 K –2 for Cu 2 SnSe 3 to 11.6 μW/cm –1 K –2 . (3) Na doping creates dense dislocation arrays and nanoprecipitates, which strengthens the phonon scattering. (4) Pair distribution function analysis shows localized symmetry breakdwon in the cubic Cu 1.85 Ag 0.15 (Sn 0.88 Ga 0.1 Na 0.02 )Se 3 . Furthermore, the present work provides a standpoint to design promising thermoelectric materials by synergistically manipulating crystal symmetry and nanoscale defects.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Random-exchange Heisenberg behavior in the electron-doped quasi-one-dimensional spin-1 chain compound AgVP 2 ⁢S 6

Recent theoretical work suggests that a pair-density wave superconducting state can be realized by doping a one-dimensional spin-1 chain. Here, we report the physical properties of single crystals of Mg x Ag 1–x VP 2 S 6 [x = 0, x = 0.017(6), x = 0.067(8), and 0.098(11)] prepared by solid-state synthesis. Single-crystal x-ray-diffraction measurements confirm that Mg 2+ is substituting for Ag + to electron dope the V 3+ zigzag chains. Magnetization measurements reveal that electron doping breaks up the V 3+ chains, resulting in unpaired spins at the chain ends. The Mg x Ag 1–x VP 2 S 6 series is consistent with random-exchange Heisenberg antiferromagnetic chain behavior and can be well described by the exchange-coupled pair model at low temperatures. As a result, transport measurements show Mg x Ag 1–x VP 2 S 6 remains insulating in the range 0 ≤ x ≤ 0.098(11), with the band gap decreasing to ~ 0.2 eV at x = 0.098(11).

1-dimensional spin chains↗
DOE OSTI2020

Energetic Stability of Freestanding and Metal-Supported Borophenes: Quantum Monte Carlo and Density-Functional Theory Calculations

Quantum Monte Carlo (QMC) and density-functional theory (DFT) calculations were carried out to study cohesion energetics of two-dimensional (2D) sheets of boron atoms called borophenes. Our QMC calculations confirmed the polymorphism among free-standing borophenes that was reported in previous DFT studies. Although Perdew-Burke-Ernzerhof (PBE) calculations significantly overestimate the cohesive energies of 2D boron sheets, DFT-PBE relative energetics with respect to each other among various free-standing borophenes are found to be in quantitative agreement with the corresponding QMC results. This suggests that one can make reliable predictions for relative stability of different boron sheets through DFT-PBE calculations. Our analysis of PBE formation energies of borophenes on metal surfaces shows that the polymorphic range is extended for borophenes on the Ag(111) and the Au(111) surfaces beyond that of free-standing borophenes, reflecting recent experimental synthesis of beta(12) and chi(3) boron sheets on the Ag(111) surface. We have also found that a hexagonal borophene can be stabilized through charge transfer from a metal surface and is energetically favored on the AI(111) surface over other borophene structures. Finally, it is found that the bilayer formation could be energetically favored over its monolayer form for the borophene-Au system, especially for borophenes with hexagonal hole densities eta lower than 1/9. This leads to our prediction that in addition to its monolayer form, a bilayer eta = 1/12 borophene can be synthesized on the Au(111) surface, opening a new possibility for borophene-based electronic devices.

ab initio↗
DOE OSTI2026

Heterogeneous doping via nanoscale coating impacts the mechanics of Li intrusion in brittle solid electrolytes

Lithium dendrite intrusion in solid-state batteries limits fast charging and causes short-circuiting, yet the underlying regulating mechanisms are not well-understood. Here, in this work, we discover that heterogeneous Ag + doping dramatically affects lithium intrusion into Li 6.6 La 3 Zr 1.6 Ta 0.4 O 12 (LLZO), a brittle solid electrolyte. Nanoscale Ag + doping is achieved by thermally annealing a 3-nm-thick metallic coating on LLZO, inducing Ag–Li ion exchange and Ag diffusion into grains and grain boundaries. Density functional theory calculations and experimental characterization show negligible impact on the electronic properties and surface wettability from Ag + incorporation. Mechanically, nanoindentation experiments show a fivefold increase in the mechanical force required to fracture the surface Ag + -doped LLZO, indicating substantial doping-induced surface toughening. Operando microprobe scanning electron microscopy experiments show that the Ag + -doped LLZO surface exhibits improved lithium plating at >250 mA cm −2 and an electroplating diameter that is expanded by over fourfold, even under an extreme indentation stress of 3 GPa. This demonstrates enhanced defect tolerance in LLZO, rather than electronic or adhesion effects. Our study reveals a chemo-mechanical mechanism via surface heterogeneous doping, complementing present bulk design rules to minimize mechanical failures in solid-state batteries.

36 MATERIALS SCIENCE↗
NASA NTRS1997

Third Order Optical Nonlinearity of Colloidal Metal Nanoclusters Formed by MeV Ion Implantation

We report the results of characterization of nonlinear refractive index of the composite material produced by MeV Ag ion implantation of LiNbO(sub 3) crystal (z-cut). The material after implantation exhibited a linear optical absorption spectrum with the surface plasmon peak near 430 nm attributed to the colloidal silver nanoclusters. Heat treatment of the material at 500 deg C caused a shift of the absorption peak to 550 nm. The nonlinear refractive index of the sample after heat treatment was measured in the region of the absorption peak with the Z-scan technique using a tunable picosecond laser source (4.5 ps pulse width).The experimental data were compared against the reference sample made of MeV Cu implanted silica with the absorption peak in the same region. The nonlinear index of the Ag implanted LiNbO(sub 3) sample produced at five times less fluence is on average two times greater than that of the reference.

Sarkisov, S. S.↗