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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Interaction of Methane with Calcium Ferrite in the Chemical Looping Partial Oxidation Application: Experimental and DFT Study

In this study, experimental studies using mass spectroscopy, thermogravimetric analysis, in situ X-ray diffraction (XRD), and theoretical density functional theory calculations were carried out to investigate the mechanism of methane partial oxidation over a CaFe 2 O 4 oxygen carrier. The XRD analysis revealed the formation of the calcium ferrite phases during methane reduction occurred in the sequence CaFe 2 O 4 →CaFe 3 O 5 + Ca 2 Fe 2 O 5 →FeO + Fe + CaO→Fe + CaO. Each of these phases was modeled using periodic density functional theory to study the activity of these phases for the reactivity with CH 4 , CO, and H 2 along with the adsorbed surface species to help elucidate the effect that phase changes during reduction have on the chemical looping products CO and H 2 . Mass spectroscopic analysis revealed the formation of H 2 O and CO 2 occurred prior to the formation of CO and H 2 , and these products may be due to the removal of lattice oxygen bound in the discrete primary phase, which contributes to a small portion (~16%) of the total transferable oxygen in the solid. The density functional theory (DFT) results suggest that the gaseous CO and H 2 are not thermodynamically favorable to react with the Ca 2 Fe 2 O 5 where the release of CO and H 2 led to an increase in selectivity for these products. The DFT results suggest that some of the adsorbed atomic hydrogen combined to form adsorbed H 2 and then gaseous H 2 on the CaFe 2 O 4 surface, while the carbon deposition and some adsorbed atomic hydrogen react to form the CaFe 3 O 5 and Ca 2 Fe 2 O 5 phases simultaneously. DFT simulations suggest that both the gaseous H 2 and adsorbed atomic H are less thermodynamically favorable to drive the deep reduction of Ca 2 Fe 2 O 5 to CaO and Fe0. The deep reduction of the calcium ferrite therefore favors the generation of syngas products (CO and H 2 ) through mechanisms of methane dehydrogenation and selective oxidation of carbon to CO. The significant difference in mechanisms for partial oxidation of methane to syngas with the CaFe 2 O 4 carrier can be correlated to the differences in the oxide phases present during the reduction process, concentration of oxygen species, and bonding in the lattice structure.

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

Little Change in Apparent Hydrological Sensitivity at Large CO 2 Forcing

Apparent hydrological sensitivity (η a ), the change in the global mean precipitation per degree K of global surface warming, is a key aspect of the climate system's response to increasing CO 2 forcing. To determine whether ηa depends on the forcing amplitude we analyze idealized experiments over a broad range of abrupt CO 2 forcing, from 2× to 8× preindustrial values, with two distinct climate models. We find little change in η a between 2× and 4×CO 2 , and almost no change beyond 5×CO 2 . We validate this finding under transient CO 2 forcing at 1%-per-year, up to 8×CO 2 . We further corroborate this result by analyzing the 1%-per-year output of more than 15 CMIP5/6 models. Lastly, we examine the 1,000-year long LongrunMIP model output, and again find little change in η a . This wealth of results demonstrates that η a is a very weak function of CO 2 forcing.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Materials Data on AgSbC6N4(OF3)2 by Materials Project

Ag(CN)4(CO)2SbF6 crystallizes in the monoclinic C2/c space group. The structure is zero-dimensional and consists of eight formaldehyde molecules, four Ag(CN)4 clusters, and four SbF6 clusters. In each Ag(CN)4 cluster, Ag1+ is bonded in a 4-coordinate geometry to four N3- atoms. There are two shorter (2.27 Å) and two longer (2.32 Å) Ag–N bond lengths. There are two inequivalent C4+ sites. In the first C4+ site, C4+ is bonded in a single-bond geometry to one N3- atom. The C–N bond length is 1.16 Å. In the second C4+ site, C4+ is bonded in a single-bond geometry to one N3- atom. The C–N bond length is 1.16 Å. There are two inequivalent N3- sites. In the first N3- site, N3- is bonded in a distorted linear geometry to one Ag1+ and one C4+ atom. In the second N3- site, N3- is bonded in a distorted linear geometry to one Ag1+ and one C4+ atom. In each SbF6 cluster, Sb3- is bonded in an octahedral geometry to six F1- atoms. There is four shorter (1.92 Å) and two longer (1.93 Å) Sb–F bond length. There are three inequivalent F1- sites. In the first F1- site, F1- is bonded in a single-bond geometry to one Sb3- atom. In the second F1- site, F1- is bonded in a single-bond geometry to one Sb3- atom. In the third F1- site, F1- is bonded in a single-bond geometry to one Sb3- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on H2Ru4(CO)13 by Materials Project

RuRu3H2(CO)9(CO)4 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of sixteen formaldehyde molecules, four ruthenium molecules, and four Ru3H2(CO)9 clusters. In two of the Ru3H2(CO)9 clusters, there are three inequivalent Ru3+ sites. In the first Ru3+ site, Ru3+ is bonded in a 5-coordinate geometry to three C+0.92+ and two H1+ atoms. There is two shorter (1.91 Å) and one longer (1.93 Å) Ru–C bond length. There is one shorter (1.77 Å) and one longer (1.78 Å) Ru–H bond length. In the second Ru3+ site, Ru3+ is bonded in a distorted rectangular see-saw-like geometry to three C+0.92+ and one H1+ atom. There is two shorter (1.90 Å) and one longer (1.91 Å) Ru–C bond length. The Ru–H bond length is 1.80 Å. In the third Ru3+ site, Ru3+ is bonded in a 4-coordinate geometry to three C+0.92+ and one H1+ atom. There is one shorter (1.90 Å) and two longer (1.92 Å) Ru–C bond length. The Ru–H bond length is 1.80 Å. There are nine inequivalent C+0.92+ sites. In the first C+0.92+ site, C+0.92+ is bonded in a single-bond geometry to one Ru3+ and one O2- atom. The C–O bond length is 1.16 Å. In the second C+0.92+ site, C+0.92+ is bonded in a single-bond geometry to one Ru3+ and one O2- atom. The C–O bond length is 1.16 Å. In the third C+0.92+ site, C+0.92+ is bonded in a single-bond geometry to one Ru3+ and one O2- atom. The C–O bond length is 1.16 Å. In the fourth C+0.92+ site, C+0.92+ is bonded in a single-bond geometry to one Ru3+ and one O2- atom. The C–O bond length is 1.16 Å. In the fifth C+0.92+ site, C+0.92+ is bonded in a single-bond geometry to one Ru3+ and one O2- atom. The C–O bond length is 1.16 Å. In the sixth C+0.92+ site, C+0.92+ is bonded in a single-bond geometry to one Ru3+ and one O2- atom. The C–O bond length is 1.16 Å. In the seventh C+0.92+ site, C+0.92+ is bonded in a single-bond geometry to one Ru3+ and one O2- atom. The C–O bond length is 1.16 Å. In the eighth C+0.92+ site, C+0.92+ is bonded in a single-bond geometry to one Ru3+ and one O2- atom. The C–O bond length is 1.16 Å. In the ninth C+0.92+ site, C+0.92+ is bonded in a single-bond geometry to one Ru3+ and one O2- atom. The C–O bond length is 1.16 Å. There are two inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a bent 120 degrees geometry to two Ru3+ atoms. In the second H1+ site, H1+ is bonded in a bent 120 degrees geometry to two Ru3+ atoms. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C+0.92+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+0.92+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one C+0.92+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one C+0.92+ atom. In the fifth O2- site, O2- is bonded in a single-bond geometry to one C+0.92+ atom. In the sixth O2- site, O2- is bonded in a single-bond geometry to one C+0.92+ atom. In the seventh O2- site, O2- is bonded in a single-bond geometry to one C+0.92+ atom. In the eighth O2- site, O2- is bonded in a single-bond geometry to one C+0.92+ atom. In the ninth O2- site, O2- is bonded in a single-bond geometry to one C+0.92+ atom. In two of the Ru3H2(CO)9 clusters, there are three inequivalent Ru3+ sites. In the first Ru3+ site, Ru3+ is bonded in a 5-coordinate geometry to three C+0.92+ and two H1+ atoms. There are a spread of Ru–C bond distances ranging from 1.90–1.93 Å. There is one shorter (1.75 Å) and one longer (1.77 Å) Ru–H bond length. In the second Ru3+ site, Ru3+ is bonded in a distorted rectangular see-saw-like geometry to three C+0.92+ and one H1+ atom. There are a spread of Ru–C bond distances ranging from 1.89–1.91 Å. The Ru–H bond length is 1.78 Å. In the third Ru3+ site, Ru3+ is bonded in a 4-coordinate geometry to three C+0.92+ and one H1+ atom. There is two shorter (1.91 Å) and one longer (1.93 Å) Ru–C bond length. The Ru–H bond length is 1.77 Å. There are nine inequivalent C+0.92+ sites. In the first C+0.92+ site, C+0.92+ is bonded in a single-bond geometry to one Ru3+ and one O2- atom. The C–O bond length is 1.16 Å. In the second C+0.92+ site, C+0.92+ is bonded in a single-bond geometry to one Ru3+ and one O2- atom. The C–O bond length is 1.16 Å. In the third C+0.92+ site, C+0.92+ is bonded in a single-bond geometry to one Ru3+ and one O2- atom. The C–O bond length is 1.16 Å. In the fourth C+0.92+ site, C+0.92+ is bonded in a single-bond geometry to one Ru3+ and one O2- atom. The C–O bond length is 1.16 Å. In the fifth C+0.92+ site, C+0.92+ is bonded in a single-bond geometry to one Ru3+ and one O2- atom. The C–O bond length is 1.16 Å. In the sixth C+0.92+ site, C+0.92+ is bonded in a single-bond geometry to one Ru3+ and one O2- atom. The C–O bond length is 1.16 Å. In the seventh C+0.92+ site, C+0.92+ is bonded in a single-bond geometry to one Ru3+ and one O2- atom. The C–O bond length is 1.16 Å. In the eighth C+0.92+ site, C+0.92+ is bonded in a single-bond geometry to one Ru3+ and one O2- atom. The C–O bond length is 1.15 Å. In the ninth C+0.92+ site, C+0.92+ is bonded in a single-bond geometry to one Ru3+ and one O2- atom. The C–O bond length is 1.16 Å. There are two inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a bent 120 degrees geometry to two Ru3+ atoms. In the second H1+ site, H1+ is bonded in a bent 120 degrees geometry to two Ru3+ atoms. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C+0.92+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+0.92+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one C+0.92+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one C+0.92+ atom. In the fifth O2- site, O2- is bonded in a single-bond geometry to one C+0.92+ atom. In the sixth O2- site, O2- is bonded in a single-bond geometry to one C+0.92+ atom. In the seventh O2- site, O2- is bonded in a single-bond geometry to one C+0.92+ atom. In the eighth O2- site, O2- is bonded in a single-bond geometry to one C+0.92+ atom. In the ninth O2- site, O2- is bonded in a single-bond geometry to one C+0.92+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2021

3D-Printable Fluoropolymer Gas Diffusion Layers for CO 2 Electroreduction

The electrosynthesis of value-added multicarbon products from CO 2 is a promising strategy to shift chemical production away from fossil fuels. Particularly important is the rational design of gas diffusion electrode (GDE) assemblies to react selectively, at scale, and at high rates. However, the understanding of the gas diffusion layer (GDL) in these assemblies is limited for the CO 2 reduction reaction (CO 2 RR): particularly important, but incompletely understood, is how the GDL modulates product distributions of catalysts operating in high current density regimes > 300 mA cm -2 . Here, 3D-printable fluoropolymer GDLs with tunable microporosity and structure are reported and probe the effects of permeance, microstructural porosity, macrostructure, and surface morphology. Under a given choice of applied electrochemical potential and electrolyte, a 100× increase in the C 2 H 4 :CO ratio due to GDL surface morphology design over a homogeneously porous equivalent and a 1.8× increase in the C 2 H 4 partial current density due to a pyramidal macrostructure are observed. Overall, these findings offer routes to improve CO 2 RR GDEs as a platform for 3D catalyst design.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CoHRu(CO)6 by Materials Project

RuCoH(CO)2(CO)4 crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of thirty-two formaldehyde molecules and four RuCoH(CO)2 clusters. In each RuCoH(CO)2 cluster, there are two inequivalent Ru2+ sites. In the first Ru2+ site, Ru2+ is bonded in a single-bond geometry to one H1+ atom. The Ru–H bond length is 1.79 Å. In the second Ru2+ site, Ru2+ is bonded in a distorted bent 120 degrees geometry to two H1+ atoms. There is one shorter (1.83 Å) and one longer (1.90 Å) Ru–H bond length. There are two inequivalent Co1+ sites. In the first Co1+ site, Co1+ is bonded in a distorted T-shaped geometry to two C+1.33+ and one H1+ atom. There is one shorter (1.75 Å) and one longer (1.77 Å) Co–C bond length. The Co–H bond length is 1.71 Å. In the second Co1+ site, Co1+ is bonded in a 3-coordinate geometry to two C+1.33+ and one H1+ atom. There is one shorter (1.75 Å) and one longer (1.78 Å) Co–C bond length. The Co–H bond length is 1.75 Å. There are four inequivalent C+1.33+ sites. In the first C+1.33+ site, C+1.33+ is bonded in a distorted linear geometry to one Co1+ and one O2- atom. The C–O bond length is 1.16 Å. In the second C+1.33+ site, C+1.33+ is bonded in a distorted linear geometry to one Co1+ and one O2- atom. The C–O bond length is 1.16 Å. In the third C+1.33+ site, C+1.33+ is bonded in a distorted linear geometry to one Co1+ and one O2- atom. The C–O bond length is 1.16 Å. In the fourth C+1.33+ site, C+1.33+ is bonded in a distorted linear geometry to one Co1+ and one O2- atom. The C–O bond length is 1.16 Å. There are two inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a water-like geometry to two Ru2+ atoms. In the second H1+ site, H1+ is bonded in a distorted L-shaped geometry to one Ru2+ and two Co1+ atoms. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C+1.33+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one C+1.33+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one C+1.33+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one C+1.33+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Real-space observation of the dissociation of a transition metal complex and its concurrent energy redistribution

Mechanistic insights into photodissociation dynamics of transition metal carbonyls, like Fe(CO) 5 , are fundamental for understanding active catalytic intermediates. Although extensively studied, the structural dynamics of these systems remain elusive. Using ultrafast X-ray scattering, we uncover the photochemistry of Fe(CO) 5 in real space and time, observing synchronous oscillations in atomic pair distances, followed by a prompt rotating CO release preferentially in the axial direction. This behavior aligns with simulations, reflecting the interplay between the axial Fe-C distances’ potential energy landscape and non-adiabatic transitions between metal-to-ligand charge-transfer states. Additionally, we characterize a secondary delayed CO release associated with a reduction of Fe-C steady state distances and structural dynamics of the formed Fe(CO) 4 . Our results quantify energy redistribution across vibration, rotation, and translation degrees of freedom, offering a microscopic view of complex structural dynamics, enhancing our grasp on Fe(CO) 5 photodissociation, and advancing our understanding of transition metal catalytic systems.

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

Crystal chemistry and phase equilibria of the CaO-½Ho 2 O 3 -CoO z system at 885 °C in air

Ini this work, the phase equilibrium diagram of the CaO-½Ho 2 O 3 -CoO z system was determined at 885 °C in air. This diagram offers compatibility relationships in the ternary oxide system that are essential for processing and for the understanding of properties of several thermoelectric phases in the system. Four three-phase regions and three solid solution tie-line regions were determined in the CaO-½Ho 2 O 3 -CoO z system. In the CaO-Ho 2 O 3 system, while a small solid solution region was identified for (Ho 1-x Ca x )O (3-z)/2 (0 ≤x ≤ 0.14), Ho was not present in the Ca site of CaO. Neither the reported Ho2CoO4 phase in the Ho 2 O-CoO z system nor the Ca-doped (Ho 1+x Ca1-x)CoO 4-z phase was present at 885 °C. No solid solution of the distorted perovskite, (Ho 1-x Cax)CoO 3-z , was established at this temperature. The CaO-CoO z system consists of two calcium cobaltate thermoelectric compounds. The 2D thermoelectric oxide, (Ca 3-x Ho x )Co 4 O 9-z (0 ≤x ≤ 0.5), has a misfit layered structure, and the 1D Ca 3 Co 2 O 6 consists of chains of alternating CoO 6 trigonal prisms and CoO 6 octahedra. Ca 3 Co 2 O 6 was found to be a stoichiometric compound. A comparison of the phase diagrams of the CaO -½ R 2 O 3 -CoO z (R = La, Nd, Eu, and Ho) systems is given.

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

Mechanistic Study of the Li–Air Battery with a Co 3 O 4 Cathode and Dimethyl Sulfoxide Electrolyte

The lithium–air battery, a powerful competitor to replace the traditional lithium-ion battery, has attracted increasing attention due to its extremely high theoretical energy density. However, its development is limited by the cathode and electrolyte properties, which should include high stability, conductivity, and electrocatalytic properties in oxygen-rich environments. Here, we employ a systematic first-principles study of Li–O 2 discharge and charge reactions on the Co 3 O 4 -based cathode with the assistance of dimethyl sulfoxide (DMSO) electrolyte. The structure, stability, and electronic properties of different surface reconstructions of the Co 3 O 4 (100) facet are investigated. In addition, the mechanisms and thermodynamic overpotentials of multi-step reactions between Li + /e – and O 2 are provided, where lithium suboxide products (Li 2 O 2 or Li 3 O 2 ) are formed on the different Co 3 O 4 (100) terminations. The solvation shell of Li + components in explicit DMSO solvent is investigated through ab initio molecular dynamics simulations. In general, we find that the Co 3 O 4 (100)-O (oxidized) surface is the most stable one under standard conditions, and the stable Li + solvation structure is found in a tetrahedral Li(DMSO) 4 + shell in the DMSO-based electrolyte. Moreover, in the system of the Co 3 O 4 (100)-O cathode and DMSO electrolyte, the solution model pathway is energetically favorable for the Li–O 2 discharge reaction. It provides a low constant overpotential of 0.17 V during a long-term discharging process, thus causing the final toroid Li 2 O 2 formation on the cathode. During the charging process, an overpotential of 0.36 V is required to rapidly decompose Li 2 O 2 .

25 ENERGY STORAGE↗
DOE OSTI2020

The crystal structures of Fe-bearing MgCO 3 sp 2 - and sp 3 -carbonates at 98 GPa from single-crystal X-ray diffraction using synchrotron radiation

The crystal structure of MgCO 3 -II has long been discussed in the literature where DFT-based model calculations predict a pressure-induced transition of the carbon atom from the sp 2 to the sp 3 type of bonding. We have now determined the crystal structure of iron-bearing MgCO 3 -II based on single-crystal X-ray diffraction measurements using synchrotron radiation. We laser-heated a synthetic (Mg 0.85 Fe 0.15 )CO 3 single crystal at 2500 K and 98 GPa and observed the formation of a monoclinic phase with composition (Mg 2.53 Fe 0.47 )C 3 O 9 in the space group C 2/ m that contains tetrahedrally coordinated carbon, where CO 4 4- tetrahedra are linked by corner-sharing oxygen atoms to form three-membered C 3 O 9 6- ring anions. The crystal structure of (Mg 0.85 Fe 0.15 )CO 3 (magnesium iron carbonate) at 98 GPa and 300 K is reported here as well. In comparison with previous structure-prediction calculations and powder X-ray diffraction data, our structural data provide reliable information from experiments regarding atomic positions, bond lengths, and bond angles.

Chariton, Stella (ORCID:0000000155220498)↗
DOE OSTI2026

Binuclear Acetoniminato Derivatives of Iron and Chromium Carbonyls: A Theoretical Study

The structures and energetics of binuclear acetoniminato metal carbonyl derivatives of the types (Me 2 C═N) 2 Fe 2 (CO) n and (Me 2 C═N) 2 Cr 2 (CO) n have been investigated by density functional theory. The (Me 2 C═N) 2 Fe 2 (CO) 6 structure, with bridging Me 2 C═N ligands using only their nitrogen atoms to bridge an Fe═Fe bond related to experimentally known species, as well as a related (Me 2 C═N) 2 Cr 2 (CO) 8 structure, appear to be energetically preferred. Among carbonyl-richer systems, the iron system energetically prefers a {Me 2 C═NC(O)} 2 Fe 2 (CO) 6 structure with bridging Me 2 C═NC(O) ligands, whereas the chromium system energetically prefers a structure with a 2,3-diazabutadiene ligand having each nitrogen atom bonded to a Cr(CO) 5 moiety. Preferred structures for systems with fewer CO groups include the tetracarbonyl (Me 2 C═N) 2 Fe 2 (CO) 4 in which one of the bridging Me 2 C═N uses its C═N double bond to bond to an iron atom, as well as (Me 2 C═N)2Cr 2 (CO) n (n = 7, 6) structures with chromium–chromium multiple bonds bridged by Me2C═N groups.

Carbonyls↗
DOE OSTI2020

Materials Data on SnH58C16S4(N11O9)2 by Materials Project

SnC6H22(N2O)4(CO(NH2)2)6(C2NH6S2O4)2 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of two dimethanesulfonamide molecules, six urea molecules, and one SnC6H22(N2O)4 cluster. In the SnC6H22(N2O)4 cluster, Sn is bonded in an octahedral geometry to two equivalent C and four O atoms. Both Sn–C bond lengths are 2.13 Å. There are two shorter (2.27 Å) and two longer (2.30 Å) Sn–O bond lengths. There are three inequivalent C sites. In the first C site, C is bonded in a trigonal planar geometry to two N and one O atom. Both C–N bond lengths are 1.35 Å. The C–O bond length is 1.29 Å. In the second C site, C is bonded in a distorted trigonal non-coplanar geometry to one Sn and three H atoms. There is one shorter (1.09 Å) and two longer (1.10 Å) C–H bond length. In the third C site, C is bonded in a trigonal planar geometry to two N and one O atom. There is one shorter (1.34 Å) and one longer (1.35 Å) C–N bond length. The C–O bond length is 1.29 Å. There are four inequivalent N sites. In the first N site, N is bonded in a trigonal planar geometry to one C and two H atoms. There is one shorter (1.02 Å) and one longer (1.03 Å) N–H bond length. In the second N site, N is bonded in a trigonal planar geometry to one C and two H atoms. There is one shorter (1.02 Å) and one longer (1.03 Å) N–H bond length. In the third N site, N is bonded in a trigonal planar geometry to one C and two H atoms. There is one shorter (1.02 Å) and one longer (1.03 Å) N–H bond length. In the fourth N site, N is bonded in a trigonal planar geometry to one C and two H atoms. Both N–H bond lengths are 1.02 Å. There are ten inequivalent H sites. In the first H site, H is bonded in a single-bond geometry to one C atom. In the second H site, H is bonded in a single-bond geometry to one N atom. In the third H site, H is bonded in a single-bond geometry to one N atom. In the fourth H site, H is bonded in a single-bond geometry to one N atom. In the fifth H site, H is bonded in a single-bond geometry to one N atom. In the sixth H site, H is bonded in a single-bond geometry to one N atom. In the seventh H site, H is bonded in a single-bond geometry to one N atom. In the eighth H site, H is bonded in a single-bond geometry to one N atom. In the ninth H site, H is bonded in a single-bond geometry to one N atom. In the tenth H site, H is bonded in a single-bond geometry to one C atom. There are two inequivalent O sites. In the first O site, O is bonded in a distorted single-bond geometry to one Sn and one C atom. In the second O site, O is bonded in a distorted bent 120 degrees geometry to one Sn and one C atom.

36 MATERIALS SCIENCE↗
DOE OSTI2026

A new layered kagome strip structure Na 2 Co 3 (AsO 4 ) 2 (OH) 2 : static and dynamic magnetic properties

One-dimensional kagome strip chains share much of the same frustrated structural motif as two-dimensional kagome antiferromagnets, making them valuable for deepening our understanding of kagome lattice magnetism. In this paper, we report the hydrothermal synthesis and detailed structural and property characterization of Na 2 Co 3 (AsO 4 ) 2 (OH) 2 , a striped kagome system. The crystal structure was characterized using single crystal X-ray diffraction which reveals that Na 2 Co 3 (AsO 4 ) 2 (OH) 2 crystallizes in monoclinic crystal system C2/m. The structure features a one-dimensional kagome strip lattice built from Co 2+ ions and undergoes an antiferromagnetic transition at T N = 14 K. The magnetic ground state at zero field was characterized using neutron powder diffraction. Below the magnetic transition, Na 2 Co 3 (AsO 4 ) 2 (OH) 2 orders into an antiferromagnetic structure with a k-vector (0.5, 0.5, 0.5). In the proposed model, the Co1 moment is predominantly confined to the ac-plane while the Co2 moment is primarily aligned along the b-axis. Two flat bands were observed in the inelastic neutron spectra below the magnetic transition, 5 and 10 meV. Inelastic neutron spectra were modeled with a Heisenberg Hamiltonian including three nearest-neighbor exchange interactions (J 1 , J 2 , J 3 ) and strong single-ion anisotropy to stabilize the observed magnetic structure. Our study highlights the complexity of Co 2+ -based kagome strip magnetic lattice compound Na 2 Co 3 (AsO 4 ) 2 (OH) 2 which provides an excellent platform to broaden our understanding of the frustrated kagome magnetic lattice space.

Liurukara, Duminda S. [Oak Ridge National Laborato↗
DOE OSTI2021

Where Is the Water? Jupiter-like C/H Ratio but Strong H{sub 2}O Depletion Found on τ Boötis b Using SPIRou

The present-day envelope of gaseous planets is a relic of how these giant planets originated and evolved. Measuring their elemental composition therefore presents a powerful opportunity to answer long-standing questions regarding planet formation. Obtaining precise observational constraints on the elemental inventory of giant exoplanets has, however, remained challenging owing to the limited simultaneous wavelength coverage of current space-based instruments. Here, we present thermal emission observations of the nontransiting hot Jupiter τ Boo b using the new wide wavelength coverage (0.95–2.50 μm) and high spectral resolution (R = 70,000) CFHT/SPIRou spectrograph. By combining a total of 20 hr of SPIRou data obtained over five nights in a full atmospheric retrieval framework designed for high-resolution data, we constrain the abundances of all the major oxygen- and carbon-bearing molecules and recover a noninverted temperature structure using a new free-shape, nonparametric temperature–pressure profile retrieval approach. We find a volume mixing ratio of log(CO) = -2.46{sub -0.29}{sup +0.25} and a highly depleted water abundance of less than 0.0072 times the expected value for a solar composition envelope. Combined with upper limits on the abundances of CH{sub 4}, CO{sub 2}, HCN, TiO, and C{sub 2}H{sub 2}, this results in a gas-phase C/H ratio of 5.85{sub -2.82}{sup +4.44} × solar, consistent with the value of Jupiter, and an envelope C/O ratio robustly greater than 0.60, even when taking into account the oxygen that may be sequestered out of the gas phase. Combined, the inferred supersolar C/H, O/H, and C/O ratios on τ Boo b support a formation scenario beyond the water snowline in a disk enriched in CO owing to pebble drift.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2023

Element-Specific Study of Magnetic Anisotropy and Hardening in SmCo 5– x Cu x Thin Films

This work investigates the effect of copper substitution on the magnetic properties of SmCo 5 thin films synthesized by molecular beam epitaxy. A series of thin films with varying concentrations of Cu were grown under otherwise identical conditions to disentangle structural and compositional effects on the magnetic behavior. The combined experimental and theoretical studies show that Cu substitution at the Co 3g sites not only stabilizes the formation of the SmCo 5 structure but also enhances magnetic anisotropy and coercivity. Density functional theory calculations indicate that Sm(Co 4 Cu 3g ) 5 possesses a higher single-ion anisotropy as compared to pure SmCo 5 . In addition, X-ray magnetic circular dichroism reveals that Cu substitution causes an increasing decoupling of the Sm 4f and Co 3d moments. Scanning transmission electron microscopy confirms predominantly SmCo 5 phase formation and reveals nanoscale inhomogeneities in the Cu and Co distribution. Our study based on thin film model systems and advanced characterization as well as modeling reveals novel aspects of the complex interplay of intrinsic and extrinsic contributions to magnetic hysteresis in rare-earth-based magnets, i.e., the combination of increased intrinsic anisotropy due to Cu substitution and the extrinsic effect of inhomogeneous elemental distribution of Cu and Co.

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DOE OSTI2025

The [4Fe-4S] Cluster of HydF Is Essential for [FeFe]-Hydrogenase Maturation

The organometallic H-cluster of the [FeFe]-hydrogenase is assembled in vivo through a complex process requiring the action of three dedicated maturation enzymes, HydG, HydE, and HydF, as well as the aminomethyl-lipoyl-H-protein (H met ) of the glycine cleavage system (GCS). Here we probe the role of HydF and its [4Fe-4S] cluster in [FeFe]-hydrogenase maturation by using a defined semisynthetic approach in which [Fe I 2 (μ-SH) 2 (CO) 4 (CN) 2 ] 2– ([2Fe] E ) is used to bypass HydE and HydG, and GCS components are used in place of cell lysate. We show that inclusion of the iron–sulfur carrier protein NfuA and the high-CO-affinity myoglobin variant Mb H64L provides dramatically improved hydrogenase activities up to 828 μmol/min/mg, equivalent to the best reported activities for Chlamydomonas reinhardtii [FeFe]-hydrogenase isolated from the native organism. Apo-HydF lacking a [4Fe-4S] cluster provides very little hydrogenase activity; however, full maturation is restored with the addition of NfuA, which we demonstrate reconstitutes the [4Fe-4S] cluster of HydF. In addition, a HydF variant lacking a [4Fe-4S] cluster by changing two cysteine ligands to alanine is completely unable to support either semisynthetic maturation using [2Fe] E , or full maturation using HydG and HydE, even in the presence of NfuA, demonstrating that the HydF [4Fe-4S] cluster is absolutely essential for [FeFe]-hydrogenase maturation. The possibility that the HydF [4Fe-4S] cluster plays a role in direct binding of [2Fe] E is negated by our results with the HydF D311C variant, which demonstrate that the labile Asp311 cluster ligand is not essential for [2Fe] E binding and HydA maturation. We therefore conclude that [2Fe]E binds HydF adjacent to, but not directly coordinated to, the [4Fe-4S] cluster. The HydF [4Fe-4S] cluster is proposed to be essential due to its impact on the [2Fe] E binding orientation and the ability of the HydF/[2Fe] E complex to form productive interactions with H met or the H met /T-protein complex during DTMA ligand biosynthesis.

cluster chemistry↗
DOE OSTI2025

Cobalt–Nickel Exchange in Exfoliated Battery Layered Cathode Sheets with Application to Recycling

With the emerging dominance of electric vehicles (EV) in the transportation sector, recycling or upcycling spent battery materials will be required to reduce EV costs, lessen waste, and ease critical material supply chain issues for EV batteries. Here, motivated by work in the literature describing the exfoliation of layered oxides, first‐principles calculations are performed to show that Li x CoO 2 , if exfoliated into nanosheets, can readily undergo transition metal cation exchange in aqueous media. The substitution of Co 3+ or Co 4+ cations inside the sheet by Ni 2+ is associated with modest reaction barriers (Δ G* ≈ 0.3–0.7 eV) and is at most mildly endothermic (Δ G ≈ 0.2–0.3 eV). In contrast, previous battery degradation studies have shown that Co 3+ diffusion is strongly inhibited inside bulk layered oxides. This suggests that processing spent layered oxides as nanosheets can provide a potentially low‐energy‐cost pathway to altering the transition metal and/or dopant stoichiometry, which can be used toward developing new room‐temperature upcycling routes for cathodes from end‐of‐life batteries.

battery recycling↗
DOE OSTI2020

Steering the Methane Dry Reforming Reactivity of Ni/La 2 O 3 Catalysts by Controlled In Situ Decomposition of Doped La 2 NiO 4 Precursor Structures

The influence of A- and/or B-site doping of Ruddlesden-Popper perovskite materials on the crystal structure, stability, and dry reforming of methane (DRM) reactivity of specific A 2 BO 4 phases (A = La, Ba; B = Cu, Ni) has been evaluated by a combination of catalytic experiments, in situ X-ray diffraction, X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), and aberration-corrected electron microscopy. At room temperature, B-site doping of La 2 NiO 4 with Cu stabilizes the orthorhombic structure ( Fmmm ) of the perovskite, while A-site doping with Ba yields a tetragonal space group ( I 4/ mmm ). We observed the orthorhombic-to-tetragonal transformation above 170 °C for La 2 Ni 0.9 Cu 0.1 O 4 and La 2 Ni 0.8 Cu 0.2 O 4 , slightly higher than for undoped La 2 NiO 4 . Loss of oxygen in interstitial sites of the tetragonal structure causes further structure transformations for all samples before decomposition in the temperature range of 400 °C-600 °C. Controlled in situ decomposition of the parent or A/B-site doped perovskite structures in a DRM mixture (CH 4 :CO 2 = 1:1) in all cases yields an active phase consisting of exsolved nanocrystalline metallic Ni particles in contact with hexagonal La 2 O 3 and a mixture of (oxy)carbonate phases (hexagonal and monoclinic La 2 O 2 CO 3 , BaCO 3 ). Differences in the catalytic activity evolve because of (i) the in situ formation of Ni-Cu alloy phases (in a composition of >7:1 = Ni:Cu) for La 2 Ni 0.9 Cu 0.1 O 4 , La 2 Ni 0.8 Cu 0.2 O 4 , and La 1.8 Ba 0.2 Ni 0.9 Cu 0.1 O 4 , (ii) the resulting Ni particle size and amount of exsolved Ni, and (iii) the inherently different reactivity of the present (oxy)carbonate species. Based on the onset temperature of catalytic DRM activity, the latter decreases in the order of La 2 Ni 0.9 Cu 0.1 O 4 ~ La 2 Ni 0.8 Cu 0.2 O 4 ≥ La 1.8 Ba 0.2 Ni 0.9 Cu 0.1 O 4 > La 2 NiO 4 > La 1.8 Ba 0.2 NiO 4 . Simple A-site doped La 1.8 Ba 0.2 NiO 4 is essentially DRM inactive. The Ni particle size can be efficiently influenced by introducing Ba into the A site of the respective Ruddlesden-Popper structures, allowing us to control the Ni particle size between 10 nm and 30 nm both for simple B-site and A-site doped structures. Hence, it is possible to steer both the extent of the metal-oxide-(oxy)carbonate interface and its chemical composition and reactivity. Counteracting the limitation of the larger Ni particle size, the activity can, however, be improved by additional Cu-doping on the B-site, enhancing the carbon reactivity. Exemplified for the La 2 NiO 4 based systems, we show how the delicate antagonistic balance of doping with Cu (rendering the La 2 NiO 4 structure less stable and suppressing coking by efficiently removing surface carbon) and Ba (rendering the La 2 NiO 4 structure more stable and forming unreactive surface or interfacial carbonates) can be used to tailor prospective DRM-active catalysts.

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