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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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11 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

A comparative study of Bi, Sb, and BiSb for electrochemical nitrogen reduction leading to a new catalyst design strategy

Recent studies identified Bi as one of the most promising non-noble metal elements that can promote the electrochemical N 2 reduction reaction (ENRR) to produce NH 3 . The electronic features that make Bi a promising ENRR catalyst may also be owned by Sb that belongs to the same group as Bi. Thus, the ENRR properties of Bi, Sb, and a BiSb alloy were investigated comparatively to identify common characteristics that facilitate the ENRR. These catalysts were prepared as uniform coating layers on high surface area carbon felt electrodes, which could serve as both regular electrodes and pseudo-gas diffusion electrodes. The experimental results demonstrated that while Bi and Sb show comparable ENRR performances, the formation of a BiSb alloy distinctively increases the faradic efficiency for NH 3 production. Additionally, the X-ray photoelectron spectroscopy results revealed that Bi in BiSb possesses a partial positive charge while Sb in BiSb possesses a partial negative charge, which can impact the way the catalyst surface interacts with the reactants and reaction intermediates of the ENRR and hydrogen evolution reaction (HER), the major competing reaction with the ENRR. Computational investigations including the Bader charge analysis and Gibbs free energy calculations for the elemental steps of the ENRR and HER provided an explanation of how the formation of a BiSb alloy can change the selectivity for the ENRR. The combined experimental and theoretical results and discussion contained in this study lead to a new strategy for designing efficient metal catalysts for the ENRR. Additionally, this study investigated how the use of gas phase and dissolved N 2 affected the ENRR performances of the Bi, Sb, and BiSb catalysts.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BiSb by Materials Project

BiSb is Halite, Rock Salt structured and crystallizes in the trigonal R3m space group. The structure is three-dimensional. Bi3+ is bonded to six equivalent Sb3- atoms to form a mixture of distorted corner and edge-sharing BiSb6 octahedra. The corner-sharing octahedral tilt angles are 12°. There are three shorter (3.03 Å) and three longer (3.53 Å) Bi–Sb bond lengths. Sb3- is bonded to six equivalent Bi3+ atoms to form a mixture of distorted corner and edge-sharing SbBi6 octahedra. The corner-sharing octahedral tilt angles are 12°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on La8(BiSb)3 by Materials Project

La8(BiSb)3 crystallizes in the monoclinic C2 space group. The structure is three-dimensional. there are four inequivalent La sites. In the first La site, La is bonded in a 6-coordinate geometry to three Bi and three Sb atoms. There are a spread of La–Bi bond distances ranging from 3.29–3.54 Å. There are a spread of La–Sb bond distances ranging from 3.23–3.49 Å. In the second La site, La is bonded in a 6-coordinate geometry to three Bi and three Sb atoms. There are a spread of La–Bi bond distances ranging from 3.28–3.53 Å. There are a spread of La–Sb bond distances ranging from 3.22–3.53 Å. In the third La site, La is bonded in a 6-coordinate geometry to three Bi and three Sb atoms. There are a spread of La–Bi bond distances ranging from 3.28–3.51 Å. There are a spread of La–Sb bond distances ranging from 3.24–3.51 Å. In the fourth La site, La is bonded in a 6-coordinate geometry to three Bi and three Sb atoms. There are a spread of La–Bi bond distances ranging from 3.29–3.55 Å. There are a spread of La–Sb bond distances ranging from 3.22–3.49 Å. There are two inequivalent Bi sites. In the first Bi site, Bi is bonded to eight La atoms to form distorted BiLa8 hexagonal bipyramids that share corners with two equivalent BiLa8 hexagonal bipyramids, corners with six SbLa8 hexagonal bipyramids, edges with four equivalent BiLa8 hexagonal bipyramids, faces with two equivalent BiLa8 hexagonal bipyramids, and faces with six SbLa8 hexagonal bipyramids. In the second Bi site, Bi is bonded to eight La atoms to form distorted BiLa8 hexagonal bipyramids that share corners with four equivalent BiLa8 hexagonal bipyramids, corners with four equivalent SbLa8 hexagonal bipyramids, edges with four equivalent SbLa8 hexagonal bipyramids, faces with four equivalent BiLa8 hexagonal bipyramids, and faces with four equivalent SbLa8 hexagonal bipyramids. There are two inequivalent Sb sites. In the first Sb site, Sb is bonded to eight La atoms to form distorted SbLa8 hexagonal bipyramids that share corners with four equivalent BiLa8 hexagonal bipyramids, corners with four equivalent SbLa8 hexagonal bipyramids, edges with four equivalent BiLa8 hexagonal bipyramids, faces with four equivalent BiLa8 hexagonal bipyramids, and faces with four equivalent SbLa8 hexagonal bipyramids. In the second Sb site, Sb is bonded to eight La atoms to form distorted SbLa8 hexagonal bipyramids that share corners with two equivalent SbLa8 hexagonal bipyramids, corners with six BiLa8 hexagonal bipyramids, edges with four equivalent SbLa8 hexagonal bipyramids, faces with two equivalent SbLa8 hexagonal bipyramids, and faces with six BiLa8 hexagonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Stable bismuth-antimony alloy cathode with a conversion-dissolution/deposition mechanism for high-performance zinc batteries

Although a large number of intercalation cathode materials for aqueous Zn batteries have been reported, limited intercalation capacity precludes achieving a higher energy density. Here, for this work, we develop a high-performance aqueous Zn battery based on BiSb alloy (Bi 0.5 Sb 0.5 ) using a high-concentrated strong-basic polyelectrolyte. We demonstrate that a conversion-dissolution/deposition electrochemical mechanism (BiSb ↔ Bi + SbO 2 – ↔ Bi + SbO 3 – ↔ Bi 2 O 3 ) through in situ X-ray diffraction (XRD), Raman, and ex-situ X-ray photoelectron spectrometry (XPS) characterizations with the help of density functional theory calculations. The BiSb cathode delivers large capacity of 512 mAh g –1 at 0.3 Ag –1 and superior rate capability of 90 mAh g –1 even at 20 Ag –1 , and long-term cyclability with capacity retentions of 184 mAh g –1 after 600 cycles at 0.5 Ag –1 and 130 mAh g –1 after 1300 cycles at 1 Ag –1 . Remarkably, even at temperatures as low as –10 and –20 °C, capacities of 210 and 197 mAh g –1 are reserved at 1 Ag –1 , respectively. Moreover, the prepared pouch Zn//BiSb battery delivers a high energy density of 303 Wh kg –1 BiSb at 0.3 Ag –1 . When coupled with a high concentration polyelectrolyte, the Zn/BiSb battery exhibits an excellent performance over a wide temperature range (–40 to 40 °C). Our research reveals the metal cathode is promising for Zn batteries to achieve a high performance with the unique mechanism and alloys can be an effective approach to stabilize metal electrodes for cycling.

25 ENERGY STORAGE↗
DOE OSTI2021

Bulk dissipation in the quantum anomalous Hall effect

Even at the lowest accessible temperatures, measurements of the quantum anomalous Hall (QAH) effect have indicated the presence of parasitic dissipative conduction channels. There is no consensus whether parasitic conduction is related to processes in the bulk or along the edges. Here, we approach this problem by comparing transport measurements of Hall bar and Corbino geometry devices fabricated from Cr-doped (BiSb) 2 Te 3 . We identify bulk conduction as the dominant source of dissipation at all values of temperature and in-plane electric field. Furthermore, we observe identical breakdown phenomenology in both geometries, indicating that breakdown of the QAH phase is a bulk process. The methodology developed in this study could be used to identify dissipative conduction mechanisms in new QAH materials, ultimately guiding material development towards realization of the QAH effect at higher temperatures

36 MATERIALS SCIENCE↗
DOE OSTI2025

Weyl semimetal phases and intrinsic spin-Hall conductivity in SbAs ordered alloys

Here, using density functional theory calculations, we investigated possible Weyl semimetal (WSM) phases in antimony arsenide ordered alloys Sb 1-x ⁢As x (x=0, 1/6, 1/3, 1/2, 2/3, 5/6, 1). We find WSM phases for all As compositions of Sb 1-x ⁢As x with broken inversion symmetry, in contrast to Bi 1-x⁢ Sb x where only compositions x=1/2 and 5/6 were predicted to exhibit WSM phases. The WSM phases in Sb 1-x ⁢As x are characterized by the presence of 12 Weyl points, located within 55 meV from the Fermi level in the case of x = 1/2. The robust spin-orbit coupling strength and Berry curvature in these alloys produce large spin-Hall conductivity in the range of 176–602 ($\hslash$/e)(S/cm), comparable to that in the BiSb alloys. Finally, Sb 0.5 ⁢As 0.5 is predicted to be almost lattice matched to GaAs(111), with the Fermi level within the gap of the semiconductor, facilitating growth and characterization, and thus, offering promising integration with conventional semiconductors.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Probing the low-temperature limit of the quantum anomalous Hall effect

Quantum anomalous Hall effect has been observed in magnetically doped topological insulators. However, full quantization, up until now, is limited within the sub–1 K temperature regime, although the material’s magnetic ordering temperature can go beyond 100 K. Here, we study the temperature limiting factors of the effect in Cr-doped (BiSb)2Te3 systems using both transport and magneto-optical methods. By deliberate control of the thin-film thickness and doping profile, we revealed that the low occurring temperature of quantum anomalous Hall effect in current material system is a combined result of weak ferromagnetism and trivial band involvement. Our findings may provide important insights into the search for high-temperature quantum anomalous Hall insulator and other topologically related phenomena.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Materials Data on Bi2Sb2Te3 by Materials Project

(BiSb)2Te3 is Caswellsilverite-like structured and crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Bi3+ is bonded to three equivalent Bi3+ and three equivalent Te2- atoms to form distorted BiBi3Te3 octahedra that share corners with three equivalent SbTe6 octahedra, corners with three equivalent TeBi3Sb3 octahedra, edges with three equivalent SbTe6 octahedra, edges with three equivalent TeBi3Sb3 octahedra, and edges with six equivalent BiBi3Te3 octahedra. The corner-sharing octahedral tilt angles are 10°. All Bi–Bi bond lengths are 3.08 Å. All Bi–Te bond lengths are 3.52 Å. Sb is bonded to six Te2- atoms to form SbTe6 octahedra that share corners with three equivalent BiBi3Te3 octahedra, corners with three equivalent SbTe6 octahedra, edges with three equivalent BiBi3Te3 octahedra, and edges with nine equivalent SbTe6 octahedra. The corner-sharing octahedra tilt angles range from 0–10°. There are three shorter (3.06 Å) and three longer (3.21 Å) Sb–Te bond lengths. There are two inequivalent Te2- sites. In the first Te2- site, Te2- is bonded to three equivalent Bi3+ and three equivalent Sb atoms to form TeBi3Sb3 octahedra that share corners with three equivalent BiBi3Te3 octahedra, corners with three equivalent TeSb6 octahedra, edges with three equivalent BiBi3Te3 octahedra, and edges with nine TeBi3Sb3 octahedra. The corner-sharing octahedra tilt angles range from 4–10°. In the second Te2- site, Te2- is bonded to six equivalent Sb atoms to form a mixture of edge and corner-sharing TeSb6 octahedra. The corner-sharing octahedral tilt angles are 4°.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Climate-Mediated Changes to Linked Terrestrial and Marine Ecosystems across the Northeast Pacific Coastal Temperate Rainforest Margin

Coastal margins are important areas of materials flux that link terrestrial and marine ecosystems. Consequently, climate-mediated changes to coastal terrestrial ecosystems and hydrologic regimes have high potential to influence nearshore ocean chemistry and food web dynamics. Research from tightly coupled, high-flux coastal ecosystems can advance understanding of terrestrial–marine links and climate sensitivities more generally. In the present article, we use the northeast Pacific coastal temperate rainforest as a model system to evaluate such links. We focus on key above- and belowground production and hydrological transport processes that control the land-to-ocean flow of materials and their influence on nearshore marine ecosystems. We evaluate how these connections may be altered by global climate change and we identify knowledge gaps in our understanding of the source, transport, and fate of terrestrial materials along this coastal margin. Finally, we propose five priority research themes in this region that are relevant for understanding coastal ecosystem links more broadly.

temperate rainforest, coastal margin, climate chan↗