Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Na”

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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Na-D line emission from rock specimens by proton bombardment - Implications for emissions from Jupiter's satellite Io

The effectiveness of low-keV range protons in producing Na line emission from selected sodium-bearing rock and mineral samples is examined. Laboratory experiments show that substantial Na-D line emission is produced by 3- to 5-keV proton bombardment of silicate and halite rock powders. It is found that emission intensity and energy efficiency are directly proportional to sodium content and are dependent on total dose, dose rate, and proton energy. Na-D photon emission is considered to emanate predominantly from sputtered sodium slightly above the target surfaces. It is concluded that the Na-D line emission directly excited during surface sputtering by Jovian magnetospheric protons appears to be an observable component in the Jovian satellite Io emission.

Nash, D. B.↗
NASA NTRS1983

A two-stage mechanism for escape of Na and K from Io

A two-stage process is presented to identify Io as the source of Na and K ions in the Io plasma torus. The Voyager I IRIS experiment recorded an SO2 abundance of 0.2 cm atm in the Io subsolar region, and further calculations determined that the S(+) and O(+) would have sufficient energy to penetrate the Io atmosphere and produce sputtering of surface atoms at a rate of 800 million/sq cm per sec. If K, Na, and S are present on the surface in cosmic proportions, then an evenly applied sputter distribution would produce the same abundances of sputtered Na and K as observed in the Na and K clouds around Io. Sputtered into the atmosphere, the ions undergo thermal Jean's escape and attain velocities of at least 2.6 km/sec. The sputtering ions are a factor of two greater on the Jupiter side than on the solar side, in agreement with asymmetries measured by the Voyager.

Summers, M. E.↗
NASA NTRS1990

Igneous origin for the Na in the cloud of Io

Mixtures of sulfur and Na-bearing silicates were heated in evacuated silica glass capsules to temperatures between 600 C and 950 C. At or above 850 C, Na-silicate glass reacts with elemental S to form a (Na, K) sulfide. Mobilization of this phase may account for the presence of Na and K on the surface of Io, and hence in the material sputtered onto the Jovian magnetosphere.

Johnson, Mary L.↗
NASA NTRS1993

Sources of Na for the Io atmosphere

The physics and geology of Io have been extensively studied, but there has been little discussion of the chemistry. Relatively little is known about Io chemistry, but there are constraints. Further, it will be a long time before improvements will result from direct observation, given the severe difficulties with the Galileo mission. Via laboratory simulation experiments, plausible thermochemical and photochemical processes which determine the nature and amounts of surface constituents of Io are explored. The well-known density of Io shows that the planet overall is rocky. Because the orbit of Io is well within the magnetosphere of Jupiter and because Io only has a thin, transient SO2 atmosphere, the surface is continually sputtered with magnetospheric ions. Complex processes ionize and accelerate the Io surface atoms to keV and MeV energies. Remarkably, only S, O, and Na ions were found by Voyager. Sputtering also produces an atomic cloud of Na and S (O not observable) with a trace of K. Both gaseous and solid SO2 are known from spectroscopic studies. A trace of H2S and possibly CO2 are present. Geologic features are interpreted in terms of elemental S, but there is no direct evidence for this constituent. We thus have a rocky planet which does not have rocks on the surface. Our general goal is to understand the cycling of Na, S, and O through the crust and atmosphere on present-day Io and to understand how Io evolved to this state. A specific objective was to determine the phases on the surface which are the source of the Na in the atmosphere of Io.

Burnett, D. S.↗
NASA NTRS1994

Formation of Na-containing molecular ions at Io

Fast sodium atoms, which appear to be associated with the motion of the magnetic 'field lines' downstream from Io (Schneider et al. 1991), are thought to be produced by dissociation of NaX(+) in Io's plasma torus. It was suggested that these molecular ions are formed near Io's exobase by electron-impact ionization and picked up be the corotating filed lines (Wilson and Schneider 1994). Because electron cooling processes dominate electron-impact ionization in Io's corona, two reactions are suggested here as sources of NaX(+) and, hence, as the ultimate sources of the observed fast Na. First, the charge-exchange cross sections for forming NaX(+) are shown to be large for plasma torus ions (O(+), S(+), O(2+), S(3+)) colliding with NaX molecules in Io's corona. Sputtering from the surface (Chrisey et al. 1988) and rapid transport to the exobase is a potential source of NaX, where X is O,S, Na, or a molecular species such as NaS or O2. Second ions of the more abundant molecules (e.g., SO(+), SO2(+), O2(+), and S2(+)) can react efficiently with atomic Na in Io's corona to form NaX(+). Here cross sections are estimated for these two processes, as well as for charge exchange in O(+) and S(+) on Na collisions.

Johnson, R. E.↗
NASA NTRS1994

Kinetic and mechanistic analysis of dinucleotide and oligonucleotide formation from the 5'-phosphorimidazolide of adenosine on Na(+)-montmorillonite

The rate constants for the condensation reaction of the 5'-phosphorimidazolide of adenosine (ImpA) to form dinucleotides and oligonucleotides have been measured in the presence of Na(+)-volclay (a Na(+)-montmorillonite) in pH 8 aqueous solution at 25 degrees C. The rates of the reaction of ImpA with an excess of adenosine 5'-monophosphoramidate (NH2pA), P1,P2-diadenosine 5',5'-pyrophosphate (A5'ppA), or adenosine 5'-monophosphate (5'-AMP or pA) in the presence of the montmorillonite to form NH2pA3'pA, A5'ppA3'pA, and pA3'pA, respectively, were measured. Only 3',5'-linked products were observed. The magnitude of the rate constants decrease in the order NH2pA3'pA > A5'-ppA3'pA > pA3'pA. The binding of ImpA to montmorillonite was measured, and the adsorption isotherm was determined. The binding of ImpA to montmorillonite and the formation of higher oligonucleotides is not observed in the absence of salts. Mg2+ enhances binding and oligonucleotide formation more than Ca2+ and Na+. The rate constants for the oligonucleotide formation were determined from the reaction products formed from 10 to 40 mM ImpA in the presence of Na(+)-montmorillonite using the computer program SIMFIT. The magnitudes of the rate constants for the formation of oligonucleotides increased in the order 2-mer < 3-mer < 4-mer ... 7-mer. The rate constants for dinucleotide and trinucleotide formation are more than 1000 times larger than those measured in the absence of montmorillonite. The rate constants for the formation of dinucleotide, trinucleotide, and tetranucleotide are 41,2.6, and 3.7 times larger than those for the formation of oligo(G)s with a poly(C) template. The hydrolysis of ImpA was accelerated 35 times in the presence of the montmorillonite. The catalytic ability of montmorillonite to form dinucleotides and oligonucleotides is quantitatively evaluated and possible pathways for oligo(A) formation are proposed.

NASA Discipline Exobiology↗
NASA NTRS2016

Observations and Simulations of the Na I D-1 Line profiles in an M-Class Solar Flare

We study the temporal evolution of the Na I D1 line profiles in the M3.9 flare SOL2014-06-11T21:03UT, using observations at high spectral resolution obtained with the Interferometric Bidimensional Spectrometer instrumentation the Dunn Solar Telescope combined with radiative hydrodynamic simulations. Our results show a significant increase in the intensities of the line core and wings during the flare. The analysis of the line profiles from the flare ribbons reveals that the Na I D1 line has a central reversal with excess emission in the blue wing (blue asymmetry).We combine RADYN and RH simulations to synthesize Na I D1 line profiles of the flaring atmosphere and find good agreement with the observations. Heating with a beam of electrons modifies the radiation field in the flaring atmosphere and excites electrons from the ground state 3s 2S to the first excited state 3p 2P, which in turn modifies the relative population of the two states. The change in temperature and the population density of the energy states make the sodium line profile revert from absorption into emission. Furthermore, the rapid changes in temperature break the pressure balance between the different layers of the lower atmosphere, generating upflow/downflow patterns. Analysis of the simulated spectra reveals that the asymmetries of the Na I D1 flare profile are produced by the velocity gradients in the lower solar atmosphere.

methods: numerical↗
DOE OSTI2020

Materials Data on Na(NO2)2 by Materials Project

NaO4N2 crystallizes in the monoclinic C2/m space group. The structure is two-dimensional and consists of two nitrogen molecules and one NaO4 sheet oriented in the (0, 0, 1) direction. In the NaO4 sheet, Na is bonded to eight equivalent O atoms to form edge-sharing NaO8 hexagonal bipyramids. There are four shorter (2.45 Å) and four longer (2.78 Å) Na–O bond lengths. O is bonded in a distorted trigonal planar geometry to two equivalent Na and one O atom. The O–O bond length is 1.29 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na(NiO2)2 by Materials Project

Na(NiO2)2 crystallizes in the monoclinic P2/c space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Na–O bond distances ranging from 2.35–2.46 Å. In the second Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are two shorter (2.35 Å) and four longer (2.44 Å) Na–O bond lengths. There are three inequivalent Ni+3.50+ sites. In the first Ni+3.50+ site, Ni+3.50+ is bonded to six O2- atoms to form edge-sharing NiO6 octahedra. There are a spread of Ni–O bond distances ranging from 1.86–1.98 Å. In the second Ni+3.50+ site, Ni+3.50+ is bonded to six O2- atoms to form edge-sharing NiO6 octahedra. There are a spread of Ni–O bond distances ranging from 1.88–1.98 Å. In the third Ni+3.50+ site, Ni+3.50+ is bonded to six O2- atoms to form edge-sharing NiO6 octahedra. There is two shorter (1.87 Å) and four longer (1.88 Å) Ni–O bond length. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded to two Na1+ and three Ni+3.50+ atoms to form distorted ONa2Ni3 trigonal bipyramids that share corners with five ONa2Ni3 trigonal bipyramids, corners with four ONaNi3 trigonal pyramids, edges with four ONa2Ni3 trigonal bipyramids, and edges with four ONaNi3 trigonal pyramids. In the second O2- site, O2- is bonded to two Na1+ and three Ni+3.50+ atoms to form distorted ONa2Ni3 trigonal bipyramids that share corners with five ONa2Ni3 trigonal bipyramids, corners with four ONaNi3 trigonal pyramids, edges with four ONa2Ni3 trigonal bipyramids, and edges with four ONaNi3 trigonal pyramids. In the third O2- site, O2- is bonded to one Na1+ and three Ni+3.50+ atoms to form distorted ONaNi3 trigonal pyramids that share corners with four ONa2Ni3 trigonal bipyramids, corners with six ONaNi3 trigonal pyramids, edges with four ONa2Ni3 trigonal bipyramids, and an edgeedge with one ONaNi3 trigonal pyramid. In the fourth O2- site, O2- is bonded to one Na1+ and three Ni+3.50+ atoms to form distorted ONaNi3 trigonal pyramids that share corners with four ONa2Ni3 trigonal bipyramids, corners with six ONaNi3 trigonal pyramids, edges with four ONa2Ni3 trigonal bipyramids, and an edgeedge with one ONaNi3 trigonal pyramid.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na(Fe2O3)4 by Materials Project

Na(Fe2O3)4 is Spinel-like structured and crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to six O2- atoms to form NaO6 octahedra that share corners with six FeO4 tetrahedra and edges with six FeO6 octahedra. There are two shorter (2.21 Å) and four longer (2.25 Å) Na–O bond lengths. In the second Na1+ site, Na1+ is bonded to six O2- atoms to form NaO6 octahedra that share corners with six equivalent FeO4 tetrahedra and edges with six FeO6 octahedra. There are four shorter (2.24 Å) and two longer (2.25 Å) Na–O bond lengths. There are seven inequivalent Fe+2.88+ sites. In the first Fe+2.88+ site, Fe+2.88+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six FeO4 tetrahedra, an edgeedge with one NaO6 octahedra, and edges with five FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.03–2.18 Å. In the second Fe+2.88+ site, Fe+2.88+ is bonded to four O2- atoms to form FeO4 tetrahedra that share a cornercorner with one NaO6 octahedra and corners with eleven FeO6 octahedra. The corner-sharing octahedra tilt angles range from 54–60°. There is one shorter (1.88 Å) and three longer (1.98 Å) Fe–O bond length. In the third Fe+2.88+ site, Fe+2.88+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six FeO4 tetrahedra, edges with two equivalent NaO6 octahedra, and edges with four FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.04–2.08 Å. In the fourth Fe+2.88+ site, Fe+2.88+ is bonded to four O2- atoms to form FeO4 tetrahedra that share corners with two equivalent NaO6 octahedra and corners with ten FeO6 octahedra. The corner-sharing octahedra tilt angles range from 50–63°. There are a spread of Fe–O bond distances ranging from 1.88–2.04 Å. In the fifth Fe+2.88+ site, Fe+2.88+ is bonded to four O2- atoms to form FeO4 tetrahedra that share corners with three equivalent NaO6 octahedra and corners with nine FeO6 octahedra. The corner-sharing octahedra tilt angles range from 54–61°. There is three shorter (1.91 Å) and one longer (2.03 Å) Fe–O bond length. In the sixth Fe+2.88+ site, Fe+2.88+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six FeO4 tetrahedra, an edgeedge with one NaO6 octahedra, and edges with five FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.05–2.11 Å. In the seventh Fe+2.88+ site, Fe+2.88+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six FeO4 tetrahedra, an edgeedge with one NaO6 octahedra, and edges with five FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.04–2.11 Å. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Na1+ and three Fe+2.88+ atoms. In the second O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Fe+2.88+ atoms. In the third O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Fe+2.88+ atoms. In the fourth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Na1+ and three Fe+2.88+ atoms. In the fifth O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Fe+2.88+ atoms. In the sixth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Fe+2.88+ atoms. In the seventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Fe+2.88+ atoms. In the eighth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Na1+ and three Fe+2.88+ atoms. In the ninth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Na1+ and three Fe+2.88+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na(SnAs)2 by Materials Project

Na(SnAs)2 crystallizes in the trigonal R-3m space group. The structure is two-dimensional and consists of three Na(SnAs)2 sheets oriented in the (0, 0, 1) direction. Na1+ is bonded to six equivalent As3- atoms to form edge-sharing NaAs6 octahedra. All Na–As bond lengths are 3.14 Å. Sn+2.50+ is bonded in a distorted T-shaped geometry to three equivalent As3- atoms. All Sn–As bond lengths are 2.72 Å. As3- is bonded to three equivalent Na1+ and three equivalent Sn+2.50+ atoms to form a mixture of corner and edge-sharing AsNa3Sn3 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na(NbS2)2 by Materials Project

Na(NbS2)2 crystallizes in the trigonal P3m1 space group. The structure is two-dimensional and consists of one Na(NbS2)2 sheet oriented in the (0, 0, 1) direction. Na1+ is bonded in a 6-coordinate geometry to six S2- atoms. There are three shorter (2.82 Å) and three longer (2.83 Å) Na–S bond lengths. There are two inequivalent Nb+3.50+ sites. In the first Nb+3.50+ site, Nb+3.50+ is bonded to six S2- atoms to form distorted edge-sharing NbS6 pentagonal pyramids. There are three shorter (2.49 Å) and three longer (2.53 Å) Nb–S bond lengths. In the second Nb+3.50+ site, Nb+3.50+ is bonded to six S2- atoms to form distorted edge-sharing NbS6 pentagonal pyramids. There are three shorter (2.49 Å) and three longer (2.53 Å) Nb–S bond lengths. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded to three equivalent Na1+ and three equivalent Nb+3.50+ atoms to form a mixture of corner, edge, and face-sharing SNa3Nb3 octahedra. In the second S2- site, S2- is bonded to three equivalent Na1+ and three equivalent Nb+3.50+ atoms to form a mixture of distorted corner, edge, and face-sharing SNa3Nb3 pentagonal pyramids. The corner-sharing octahedral tilt angles are 41°. In the third S2- site, S2- is bonded in a distorted T-shaped geometry to three equivalent Nb+3.50+ atoms. In the fourth S2- site, S2- is bonded in a distorted T-shaped geometry to three equivalent Nb+3.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na(NbSe2)2 by Materials Project

Na(NbSe2)2 crystallizes in the trigonal P3m1 space group. The structure is two-dimensional and consists of one Na(NbSe2)2 sheet oriented in the (0, 0, 1) direction. Na1+ is bonded in a 6-coordinate geometry to six Se2- atoms. There are three shorter (2.96 Å) and three longer (2.97 Å) Na–Se bond lengths. There are two inequivalent Nb+3.50+ sites. In the first Nb+3.50+ site, Nb+3.50+ is bonded to six Se2- atoms to form distorted edge-sharing NbSe6 pentagonal pyramids. There are three shorter (2.62 Å) and three longer (2.65 Å) Nb–Se bond lengths. In the second Nb+3.50+ site, Nb+3.50+ is bonded to six Se2- atoms to form distorted edge-sharing NbSe6 pentagonal pyramids. There are three shorter (2.62 Å) and three longer (2.65 Å) Nb–Se bond lengths. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to three equivalent Na1+ and three equivalent Nb+3.50+ atoms to form a mixture of distorted edge, face, and corner-sharing SeNa3Nb3 octahedra. In the second Se2- site, Se2- is bonded to three equivalent Na1+ and three equivalent Nb+3.50+ atoms to form a mixture of distorted edge, face, and corner-sharing SeNa3Nb3 pentagonal pyramids. The corner-sharing octahedral tilt angles are 40°. In the third Se2- site, Se2- is bonded in a 3-coordinate geometry to three equivalent Nb+3.50+ atoms. In the fourth Se2- site, Se2- is bonded in a 3-coordinate geometry to three equivalent Nb+3.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na(SmS2)3 by Materials Project

SmNa(SmS2)2(S)2 crystallizes in the orthorhombic Cmmm space group. The structure is two-dimensional and consists of four hydrogen sulfide molecules; two samario molecules; and one Na(SmS2)2 sheet oriented in the (0, 0, 1) direction. In the Na(SmS2)2 sheet, Na1+ is bonded in a distorted rectangular see-saw-like geometry to four equivalent S+1.33- atoms. All Na–S bond lengths are 2.79 Å. Sm+2.33+ is bonded in a linear geometry to two equivalent S+1.33- atoms. Both Sm–S bond lengths are 2.49 Å. S+1.33- is bonded in a distorted linear geometry to one Na1+ and one Sm+2.33+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na(WO3)2 by Materials Project

Na(WO3)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to twelve O2- atoms to form NaO12 cuboctahedra that share corners with four equivalent NaO12 cuboctahedra, faces with two equivalent NaO12 cuboctahedra, and faces with eight equivalent WO6 octahedra. There are eight shorter (2.64 Å) and four longer (2.94 Å) Na–O bond lengths. In the second Na1+ site, Na1+ is bonded to twelve O2- atoms to form NaO12 cuboctahedra that share corners with four equivalent NaO12 cuboctahedra, faces with two equivalent NaO12 cuboctahedra, and faces with eight equivalent WO6 octahedra. There are four shorter (2.58 Å) and eight longer (2.82 Å) Na–O bond lengths. W+5.50+ is bonded to six O2- atoms to form WO6 octahedra that share corners with six equivalent WO6 octahedra and faces with four NaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 8–11°. All W–O bond lengths are 1.96 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to two Na1+ and two equivalent W+5.50+ atoms. In the second O2- site, O2- is bonded in a 4-coordinate geometry to two Na1+ and two equivalent W+5.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na(VSe2)2 by Materials Project

Na(VSe2)2 is MAX Phase-like structured and crystallizes in the trigonal R3m space group. The structure is two-dimensional and consists of three Na(VSe2)2 sheets oriented in the (0, 0, 1) direction. Na1+ is bonded in a 6-coordinate geometry to six Se2- atoms. There are three shorter (2.99 Å) and three longer (3.00 Å) Na–Se bond lengths. There are two inequivalent V+3.50+ sites. In the first V+3.50+ site, V+3.50+ is bonded to six Se2- atoms to form edge-sharing VSe6 octahedra. There are three shorter (2.52 Å) and three longer (2.59 Å) V–Se bond lengths. In the second V+3.50+ site, V+3.50+ is bonded to six Se2- atoms to form edge-sharing VSe6 octahedra. There are three shorter (2.52 Å) and three longer (2.59 Å) V–Se bond lengths. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to three equivalent Na1+ and three equivalent V+3.50+ atoms to form a mixture of face, edge, and corner-sharing SeNa3V3 octahedra. In the second Se2- site, Se2- is bonded in a distorted T-shaped geometry to three equivalent V+3.50+ atoms. In the third Se2- site, Se2- is bonded to three equivalent Na1+ and three equivalent V+3.50+ atoms to form a mixture of distorted face, edge, and corner-sharing SeNa3V3 pentagonal pyramids. The corner-sharing octahedral tilt angles are 41°. In the fourth Se2- site, Se2- is bonded in a distorted T-shaped geometry to three equivalent V+3.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2022

TiO x -supported Na-Mn-W oxides for the oxidative coupling of methane

Supported Na-Mn-W oxides are among the most studied catalysts for the oxidative coupling of methane (OCM) because of their superior thermal stability and relatively high C 2+ product yields. However, because of the structural complexity, the roles of each component in these catalysts have been controversial. In this work, WO x and MnO x sites were supported on titanate nanowires and employed in OCM studies. Compared to the commonly studied silica support, which is subject to severe restructuring due to the Na-induced crystallization, titanate support not only serves as a reservoir for alkali metals (e.g., Na), but also stabilizes isolated MnO x species. The catalytic performance of the titanate-based catalyst is similar to that of reference catalyst, MnO x /Na 2 WO 4 /SiO 2 , with a synergistic effect between MnO x and WO x sites. Further, advanced electron microscopy, X-ray diffraction, infrared spectroscopy, and X-ray absorption near edge structure spectroscopy suggest that the basic NaO x and MnO x species have strong interactions with the acidic WO x and TiO x species, which might contribute to the high selectivity toward C 2+ products and suppressed CO x formation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

On the Electrochemical Properties of Carbon-Coated NaCrO 2 for Na-Ion Batteries

NaCrO 2 is a promising cathode for Na-ion batteries. However, further studies of the mechanisms controlling its specific capacities and cycle stability are needed for real-world applications in the future. This study reveals, for the first time, that the typical specific capacity of ~110 mAh/g reported by many researchers when the charge/discharge voltage window is set between 2.0 and 3.6 V vs. Na/Na + is actually controlled by the low electronic conductivity at the electrode/electrolyte interface. Through wet solution mixing of NaCrO 2 particles with carbon precursors, uniform carbon coating can be formed on the surface of NaCrO 2 particles, leading to unprecedented specific capacities at 140 mAh/g, which is the highest specific capacity ever reported in the literature with the lower and upper cutoff voltages at the aforementioned values. However, such carbon-coated NaCrO 2 with ultrahigh specific capacity does not improve cycle stability because with the specific capacity at 140 mAh/g the Na deintercalation during charge is more than 50% Na ions per formula unit of NaCrO 2 which leads to irreversible redox reactions. The insights from this study provide a future direction to enhance the long-term cycle stability of NaCrO 2 through integrating carbon coating and doping.

25 ENERGY STORAGE↗