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At least 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

CO 2 Hydrogenation: Na Doping Promotes CO and Hydrocarbon Formation over Ru/m-ZrO 2 at Elevated Pressures in Gas Phase Media

Sodium-promoted monoclinic zirconia supported ruthenium catalysts were tested for CO 2 hydrogenation at 20 bar and a H 2 :CO 2 ratio of 3:1. Although increasing sodium promotion, from 2.5% to 5% by weight, slightly decreased CO 2 conversion (14% to 10%), it doubled the selectivity to both CO (~36% to ~71%) and chain growth products (~4% to ~8%) remarkably and reduced the methane selectivity by two-thirds (~60% to ~21%). For CO 2 hydrogenation during in situ DRIFTS under atmospheric pressure, it was revealed that Na increases the catalyst basicity and suppresses the reactivity of Ru sites. Higher basicity facilitates CO 2 adsorption, weakens the C–H bond of the formate intermediate promoting CO formation, and inhibits methanation occurring on ruthenium nanoparticle surfaces. The suppression of excessive hydrogenation increases the chain growth probability. Decelerated reduction during H 2 -TPR/TPR-MS and H 2 -TPR-EXAFS/XANES at the K-edge of ruthenium indicates that sodium is in contact with ruthenium. A comparison of the XANES spectra of unpromoted and Na-promoted catalysts after H 2 reduction showed no evidence of a promoting effect involving electron charge transfer.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na(FeSb3)4 by Materials Project

NaFe4Sb12 crystallizes in the cubic Im-3 space group. The structure is three-dimensional. Na1+ is bonded to twelve equivalent Sb1- atoms to form NaSb12 cuboctahedra that share faces with eight equivalent FeSb6 octahedra. All Na–Sb bond lengths are 3.41 Å. Fe+2.75+ is bonded to six equivalent Sb1- atoms to form FeSb6 octahedra that share corners with six equivalent FeSb6 octahedra and faces with two equivalent NaSb12 cuboctahedra. The corner-sharing octahedral tilt angles are 52°. All Fe–Sb bond lengths are 2.56 Å. Sb1- is bonded in a 2-coordinate geometry to one Na1+, two equivalent Fe+2.75+, and two equivalent Sb1- atoms. There are one shorter (2.97 Å) and one longer (3.06 Å) Sb–Sb bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na(CuO)2 by Materials Project

NaCu2O2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Na1+ is bonded to five O2- atoms to form distorted edge-sharing NaO5 square pyramids. There are two shorter (2.32 Å) and three longer (2.39 Å) Na–O bond lengths. There are two inequivalent Cu+1.50+ sites. In the first Cu+1.50+ site, Cu+1.50+ is bonded in a square co-planar geometry to four O2- atoms. There are two shorter (1.99 Å) and two longer (2.02 Å) Cu–O bond lengths. In the second Cu+1.50+ site, Cu+1.50+ is bonded in a linear geometry to two O2- atoms. There is one shorter (1.85 Å) and one longer (1.87 Å) Cu–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to three equivalent Na1+ and three Cu+1.50+ atoms to form ONa3Cu3 octahedra that share corners with seven equivalent ONa2Cu3 square pyramids, edges with four equivalent ONa3Cu3 octahedra, and edges with two equivalent ONa2Cu3 square pyramids. In the second O2- site, O2- is bonded to two equivalent Na1+ and three Cu+1.50+ atoms to form ONa2Cu3 square pyramids that share corners with seven equivalent ONa3Cu3 octahedra, edges with two equivalent ONa3Cu3 octahedra, and edges with two equivalent ONa2Cu3 square pyramids. The corner-sharing octahedra tilt angles range from 0–76°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na(RhO2)2 by Materials Project

NaRh2O4 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Na1+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Na–O bond distances ranging from 2.42–2.55 Å. There are two inequivalent Rh+3.50+ sites. In the first Rh+3.50+ site, Rh+3.50+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing RhO6 octahedra. The corner-sharing octahedra tilt angles range from 50–59°. There are a spread of Rh–O bond distances ranging from 2.02–2.07 Å. In the second Rh+3.50+ site, Rh+3.50+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing RhO6 octahedra. The corner-sharing octahedra tilt angles range from 50–59°. There are two shorter (2.04 Å) and four longer (2.06 Å) Rh–O bond lengths. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 5-coordinate geometry to two equivalent Na1+ and three Rh+3.50+ atoms. In the second O2- site, O2- is bonded to two equivalent Na1+ and three equivalent Rh+3.50+ atoms to form a mixture of distorted edge and corner-sharing ONa2Rh3 square pyramids. In the third O2- site, O2- is bonded to two equivalent Na1+ and three Rh+3.50+ atoms to form a mixture of distorted edge and corner-sharing ONa2Rh3 trigonal bipyramids. In the fourth O2- site, O2- is bonded in a 5-coordinate geometry to two equivalent Na1+ and three equivalent Rh+3.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na(CuO)2 by Materials Project

NaCu2O2 crystallizes in the tetragonal P4_2/nmc space group. The structure is three-dimensional. Na1+ is bonded to five O2- atoms to form edge-sharing NaO5 square pyramids. There are a spread of Na–O bond distances ranging from 2.31–2.40 Å. There are two inequivalent Cu+1.50+ sites. In the first Cu+1.50+ site, Cu+1.50+ is bonded in a square co-planar geometry to four O2- atoms. There are two shorter (2.00 Å) and two longer (2.03 Å) Cu–O bond lengths. In the second Cu+1.50+ site, Cu+1.50+ is bonded in a linear geometry to two O2- atoms. There is one shorter (1.85 Å) and one longer (1.86 Å) Cu–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to three equivalent Na1+ and three Cu+1.50+ atoms to form ONa3Cu3 octahedra that share corners with seven equivalent ONa2Cu3 square pyramids, edges with four equivalent ONa3Cu3 octahedra, and edges with two equivalent ONa2Cu3 square pyramids. In the second O2- site, O2- is bonded to two equivalent Na1+ and three Cu+1.50+ atoms to form distorted ONa2Cu3 square pyramids that share corners with seven equivalent ONa3Cu3 octahedra, edges with two equivalent ONa3Cu3 octahedra, and edges with two equivalent ONa2Cu3 square pyramids. The corner-sharing octahedra tilt angles range from 0–80°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na(Cu2Sb)2 by Materials Project

NaCu4Sb2 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Na1+ is bonded to six equivalent Sb3- atoms to form edge-sharing NaSb6 octahedra. All Na–Sb bond lengths are 3.26 Å. There are two inequivalent Cu+1.25+ sites. In the first Cu+1.25+ site, Cu+1.25+ is bonded in a 1-coordinate geometry to three equivalent Cu+1.25+ and four equivalent Sb3- atoms. All Cu–Cu bond lengths are 2.56 Å. There are one shorter (2.70 Å) and three longer (2.88 Å) Cu–Sb bond lengths. In the second Cu+1.25+ site, Cu+1.25+ is bonded in a trigonal non-coplanar geometry to three equivalent Cu+1.25+ and three equivalent Sb3- atoms. All Cu–Sb bond lengths are 2.60 Å. Sb3- is bonded in a 10-coordinate geometry to three equivalent Na1+ and seven Cu+1.25+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na(Mo3Se4)2 by Materials Project

Na1Mo6Se8 crystallizes in the trigonal R-3 space group. The structure is three-dimensional. Na1+ is bonded in a body-centered cubic geometry to eight Se2- atoms. There are two shorter (2.80 Å) and six longer (3.25 Å) Na–Se bond lengths. Mo+2.50+ is bonded to five Se2- atoms to form a mixture of corner and edge-sharing MoSe5 square pyramids. There are a spread of Mo–Se bond distances ranging from 2.53–2.74 Å. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 1-coordinate geometry to one Na1+ and three equivalent Mo+2.50+ atoms. In the second Se2- site, Se2- is bonded in a 5-coordinate geometry to one Na1+ and four equivalent Mo+2.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na(CoO2)2 by Materials Project

NaCo2O4 crystallizes in the orthorhombic Amm2 space group. The structure is two-dimensional and consists of one NaCo2O4 sheet oriented in the (0, 0, 1) direction. Na1+ is bonded to six equivalent O2- atoms to form distorted NaO6 pentagonal pyramids that share corners with six equivalent CoO6 octahedra, edges with six equivalent CoO6 octahedra, and edges with six equivalent NaO6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 9–12°. There are two shorter (2.36 Å) and four longer (2.38 Å) Na–O bond lengths. Co+3.50+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with three equivalent NaO6 pentagonal pyramids, edges with six equivalent CoO6 octahedra, and edges with three equivalent NaO6 pentagonal pyramids. There are a spread of Co–O bond distances ranging from 1.88–2.16 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to three equivalent Na1+ and three equivalent Co+3.50+ atoms to form a mixture of edge, corner, and face-sharing ONa3Co3 octahedra. The corner-sharing octahedra tilt angles range from 41–47°. In the second O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three equivalent Co+3.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na(Mo2O3)2 by Materials Project

NaMo4O6 crystallizes in the tetragonal P4/mbm space group. The structure is three-dimensional. Na1+ is bonded in a body-centered cubic geometry to eight equivalent O2- atoms. All Na–O bond lengths are 3.05 Å. There are two inequivalent Mo+2.75+ sites. In the first Mo+2.75+ site, Mo+2.75+ is bonded in a see-saw-like geometry to four O2- atoms. There are two shorter (2.05 Å) and two longer (2.12 Å) Mo–O bond lengths. In the second Mo+2.75+ site, Mo+2.75+ is bonded to five O2- atoms to form edge-sharing MoO5 square pyramids. There are one shorter (2.03 Å) and four longer (2.15 Å) Mo–O bond lengths. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a trigonal planar geometry to three Mo+2.75+ atoms. In the second O2- site, O2- is bonded in a 5-coordinate geometry to two equivalent Na1+ and three Mo+2.75+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na(MoO2)3 by Materials Project

NaMo2O4MoO2 crystallizes in the orthorhombic Cmmm space group. The structure is two-dimensional and consists of two molybdenum molecules; four water molecules; and one NaMo2O4 sheet oriented in the (0, 0, 1) direction. In the NaMo2O4 sheet, Na1+ is bonded in a square co-planar geometry to four equivalent O2- atoms. All Na–O bond lengths are 2.34 Å. Mo+3.67+ is bonded in a linear geometry to two equivalent O2- atoms. Both Mo–O bond lengths are 1.81 Å. O2- is bonded in a bent 150 degrees geometry to one Na1+ and one Mo+3.67+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na(GeP)3 by Materials Project

NaGe3P3 crystallizes in the orthorhombic Pmc2_1 space group. The structure is three-dimensional. Na1+ is bonded to five P3- atoms to form distorted NaP5 square pyramids that share corners with six equivalent GeP4 tetrahedra and edges with two equivalent NaP5 square pyramids. There are a spread of Na–P bond distances ranging from 2.96–3.14 Å. There are three inequivalent Ge+2.67+ sites. In the first Ge+2.67+ site, Ge+2.67+ is bonded in a water-like geometry to two equivalent P3- atoms. Both Ge–P bond lengths are 2.42 Å. In the second Ge+2.67+ site, Ge+2.67+ is bonded in a distorted trigonal non-coplanar geometry to three P3- atoms. There are one shorter (2.39 Å) and two longer (2.41 Å) Ge–P bond lengths. In the third Ge+2.67+ site, Ge+2.67+ is bonded to four P3- atoms to form GeP4 tetrahedra that share corners with six equivalent NaP5 square pyramids and corners with two equivalent GeP4 tetrahedra. There are a spread of Ge–P bond distances ranging from 2.34–2.36 Å. There are three inequivalent P3- sites. In the first P3- site, P3- is bonded to one Na1+ and three Ge+2.67+ atoms to form distorted PNaGe3 trigonal pyramids that share corners with four equivalent PNa2Ge3 trigonal bipyramids and corners with two equivalent PNaGe3 trigonal pyramids. In the second P3- site, P3- is bonded in a distorted pentagonal planar geometry to two equivalent Na1+ and three Ge+2.67+ atoms. In the third P3- site, P3- is bonded to two equivalent Na1+ and three Ge+2.67+ atoms to form distorted PNa2Ge3 trigonal bipyramids that share corners with four equivalent PNaGe3 trigonal pyramids and edges with two equivalent PNa2Ge3 trigonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na(CoO2)2 by Materials Project

NaCo2O4 crystallizes in the trigonal R3m space group. The structure is two-dimensional and consists of three NaCo2O4 sheets oriented in the (0, 0, 1) direction. Na1+ is bonded to six O2- atoms to form distorted NaO6 pentagonal pyramids that share corners with nine CoO6 octahedra, edges with three equivalent CoO6 octahedra, edges with six equivalent NaO6 pentagonal pyramids, and a faceface with one CoO6 octahedra. The corner-sharing octahedra tilt angles range from 8–47°. There are three shorter (2.35 Å) and three longer (2.42 Å) Na–O bond lengths. There are two inequivalent Co+3.50+ sites. In the first Co+3.50+ site, Co+3.50+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with three equivalent NaO6 pentagonal pyramids, edges with six equivalent CoO6 octahedra, and edges with three equivalent NaO6 pentagonal pyramids. There are three shorter (1.93 Å) and three longer (2.11 Å) Co–O bond lengths. In the second Co+3.50+ site, Co+3.50+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with six equivalent NaO6 pentagonal pyramids, edges with six equivalent CoO6 octahedra, and a faceface with one NaO6 pentagonal pyramid. There are three shorter (1.94 Å) and three longer (2.08 Å) Co–O bond lengths. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a trigonal non-coplanar geometry to three equivalent Co+3.50+ atoms. In the second O2- site, O2- is bonded in a 6-coordinate geometry to three equivalent Na1+ and three equivalent Co+3.50+ atoms. In the third O2- site, O2- is bonded in a trigonal non-coplanar geometry to three equivalent Co+3.50+ atoms. In the fourth O2- site, O2- is bonded to three equivalent Na1+ and three equivalent Co+3.50+ atoms to form edge-sharing ONa3Co3 octahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na(RuO2)2 by Materials Project

NaRu2O4 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Na1+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Na–O bond distances ranging from 2.37–2.67 Å. There are two inequivalent Ru+3.50+ sites. In the first Ru+3.50+ site, Ru+3.50+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing RuO6 octahedra. The corner-sharing octahedra tilt angles range from 45–54°. There are a spread of Ru–O bond distances ranging from 2.00–2.07 Å. In the second Ru+3.50+ site, Ru+3.50+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing RuO6 octahedra. The corner-sharing octahedra tilt angles range from 45–54°. There are a spread of Ru–O bond distances ranging from 2.01–2.07 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 5-coordinate geometry to two equivalent Na1+ and three Ru+3.50+ atoms. In the second O2- site, O2- is bonded to two equivalent Na1+ and three equivalent Ru+3.50+ atoms to form a mixture of distorted edge and corner-sharing ONa2Ru3 square pyramids. In the third O2- site, O2- is bonded in a 5-coordinate geometry to two equivalent Na1+ and three Ru+3.50+ atoms. In the fourth O2- site, O2- is bonded to two equivalent Na1+ and three equivalent Ru+3.50+ atoms to form a mixture of distorted edge and corner-sharing ONa2Ru3 trigonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2024

High–Energy Earth–Abundant Cathodes with Enhanced Cationic/Anionic Redox for Sustainable and Long–Lasting Na–Ion Batteries

Layered iron/manganese-based oxides are a class of promising cathode materials for sustainable batteries due to their high energy densities and earth abundance. However, the stabilization of cationic and anionic redox reactions in these cathodes during cycling at high voltage remain elusive. Here, an electrochemically/thermally stable P2-Na 0.67 Fe 0.3 Mn 0.5 Mg 0.1 Ti 0.1 O 2 cathode material with zero critical elements is designed for sodium-ion batteries (NIBs) to realize a highly reversible capacity of ≈210 mAh g –1 at 20 mA g –1 and good cycling stability with a capacity retention of 74% after 300 cycles at 200 mA g –1 , even when operated with a high charge cut-off voltage of 4.5 V versus sodium metal. Combining a suite of cutting-edge characterizations and computational modeling, it is shown that Mg/Ti co-doping leads to stabilized surface/bulk structure at high voltage and high temperature, and more importantly, enhances cationic/anionic redox reaction reversibility over extended cycles with the suppression of other undesired oxygen activities. This work fundamentally deepens the failure mechanism of Fe/Mn-based layered cathodes and highlights the importance of dopant engineering to achieve high-energy and earth-abundant cathode material for sustainable and long-lasting NIBs.

25 ENERGY STORAGE↗
DOE OSTI2025

Revisiting Structural and Electromechanical Properties of the Lead-free (K,Na)NbO 3 High-Piezoelectric Material

Having lead-free systems with excellent piezoelectric responses is crucial to the development of environmentally friendly electromechanical applications. In this work, we build an effective Hamiltonian model to explore the promising (K x Na 1–x )NbO 3 system, whose rich phase diagram near x = 50% remains poorly understood meanwhile exhibiting a colossal effective piezoelectric response. Thanks to the numerical implementation of this effective Hamiltonian scheme into a Monte Carlo Metropolis algorithm, we reveal striking features. First, a long-period state can be the ground state at low temperatures for some concentrations while only a short-period conventional polar ground state exists for larger x. Second, the electric field-driven transformation, via a first-order transition, of this long-period state into a short-period polar state creates large electromechanical strains (on the order of the percent) and is likely the origin of the colossal piezoelectric response reported in KNN, for which we evaluate an effective piezoelectric coefficient of several thousands of pC/N.

(K,Na)NbO3↗
DOE OSTI2025

Determination of nuclear charge radius by extreme-ultraviolet spectroscopy of Na-like ions

We report on a method for determining the absolute nuclear charge radius of high-𝑍 elements using extreme-ultraviolet spectroscopy of highly charged Na-like ions in tandem with highly accurate atomic structure calculations of transition energy differences. The application of this method has reduced the nuclear charge radius uncertainty of 191 Ir by a factor of 8 from the currently accepted literature value, with a recently reported charge radius of 5.435(12) fm. The result reduces the charge radius uncertainty along the full Ir isotopic chain when combined with prior optical isotope shift measurements. The technique utilizes only a few million ions stored in an ion trap, which should apply to measurements with small quantities of radioactive nuclei.

Atom & ion trapping & guiding↗
DOE OSTI2025

Development of a kinetic-thermodynamic model for lime-stabilization of Na-bentonite

This study presents the first kinetic model to predict the solid and pore solution composition of Na-bentonite clay reacting with slaked lime over a period of 720 days. The model successfully accounts for most experimental data using a single kinetic rate constant. The following sequence of reactions was predicted by the model: initial rapid dissolution of portlandite within the first 7 days, leading to a decrease in pH and dissolved calcium, and concurrent formation of calcium silicate hydrates (C-S-H: jennite), calcium aluminate hydrate (C-A-H: C₄AH₁₃), calcium aluminosilicate hydrates (stratlingite) and hydrotalcite. After 7 days, jennite and stratlingite are predicted to transform into tobermorite-II, contributing to strength development up to 28 days. From 28 to 90 days, continued montmorillonite dissolution is predicted, along with minor formation of ettringite, partial tobermorite-II dissolution, and precipitation of secondary phases such as albite and talc. Experimentally, portlandite dissolution was confirmed by TGA and XRD and found to be complete within 7 days, in agreement with model predictions. However, other predicted solid-phase transformations (e.g., tobermorite-II formation and dissolution, ettringite, albite, and talc formation) could not be conclusively verified through experimental techniques. Aqueous phase measurements confirmed that the pH and Ca trends in solution, and that equilibrium was reached by 90 days.

Chemical kinetics↗
DOE OSTI2024

Deconstructing the High Voltage Degradation Mechanisms in Na 2/3 Ni 1/3 Mn 2/3 O 2 with Single Crystals and Advanced Electrolyte

Abstract Sodium layered oxide cathodes can uniquely benefit from the existing lithium‐ion battery industry as sodium‐ion batteries gain traction as a potential low‐cost, drop‐in replacement. However, achieving relevant energy density with a suitable cycle life remains a challenge for sodium layered oxides. At high operating potentials, several competing degradation mechanisms prevent P2‐type Na 2/3 Ni 1/3 Mn 2/3 O 2 (≈550 Wh kg −1 ) from achieving meaningful cycle life—with bulk structural instability and surface reactivity being the primary retractors. Herein, the issue of particle cracking is addressed through detailed synthesis methods of “single‐crystal” materials. By comparison to a polycrystalline baseline, the single‐crystal materials quantify the capacity loss due to isolation of active material caused by intergranular particle cracking. The single crystal materials are then employed in cells with an advanced, “localized saturated electrolyte” (LSE) to demonstrate the magnitude of capacity loss due to electrolyte decomposition at the cathode surface. Mitigation of the surface reactivity through the LSE electrolyte effectively demonstrates the elevated importance of surface reactivity at high voltages despite the onset of egregious particle cracking. This work aims to guide future research into understanding molten‐salt assisted syntheses and advance the debate on surface versus bulk degradation.

Darga, Joe↗