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At least 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Er4Ge6Rh7 by Materials Project

Er4Rh7Ge6 crystallizes in the cubic Im-3m space group. The structure is three-dimensional. Er is bonded to six equivalent Rh and six equivalent Ge atoms to form ErGe6Rh6 cuboctahedra that share corners with twelve equivalent ErGe6Rh6 cuboctahedra, faces with six equivalent ErGe6Rh6 cuboctahedra, and faces with two equivalent RhGe6 octahedra. All Er–Rh bond lengths are 2.96 Å. All Er–Ge bond lengths are 3.02 Å. There are two inequivalent Rh sites. In the first Rh site, Rh is bonded to six equivalent Ge atoms to form RhGe6 octahedra that share faces with eight equivalent ErGe6Rh6 cuboctahedra. All Rh–Ge bond lengths are 2.67 Å. In the second Rh site, Rh is bonded in a 12-coordinate geometry to four equivalent Er and four equivalent Ge atoms. All Rh–Ge bond lengths are 2.59 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Er and five Rh atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tb4InGe4Rh by Materials Project

Tb4RhInGe4 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are four inequivalent Tb sites. In the first Tb site, Tb is bonded in a 6-coordinate geometry to two equivalent Rh and six Ge atoms. Both Tb–Rh bond lengths are 3.37 Å. There are a spread of Tb–Ge bond distances ranging from 2.95–3.03 Å. In the second Tb site, Tb is bonded in a 11-coordinate geometry to three equivalent Rh, two equivalent In, and six Ge atoms. There are one shorter (3.10 Å) and two longer (3.13 Å) Tb–Rh bond lengths. Both Tb–In bond lengths are 3.41 Å. There are a spread of Tb–Ge bond distances ranging from 2.95–3.11 Å. In the third Tb site, Tb is bonded in a 9-coordinate geometry to one Rh, two equivalent In, and six Ge atoms. The Tb–Rh bond length is 3.25 Å. Both Tb–In bond lengths are 3.39 Å. There are a spread of Tb–Ge bond distances ranging from 2.98–3.11 Å. In the fourth Tb site, Tb is bonded in a 10-coordinate geometry to four In and six Ge atoms. There are two shorter (3.44 Å) and two longer (3.48 Å) Tb–In bond lengths. There are a spread of Tb–Ge bond distances ranging from 2.97–3.23 Å. Rh is bonded in a 4-coordinate geometry to six Tb and four Ge atoms. There are a spread of Rh–Ge bond distances ranging from 2.49–2.58 Å. There are two inequivalent In sites. In the first In site, In is bonded to eight Tb and four Ge atoms to form a mixture of corner and face-sharing InTb8Ge4 cuboctahedra. There are two shorter (2.88 Å) and two longer (3.13 Å) In–Ge bond lengths. In the second In site, In is bonded to eight Tb and four Ge atoms to form a mixture of corner and face-sharing InTb8Ge4 cuboctahedra. There are two shorter (2.87 Å) and two longer (2.92 Å) In–Ge bond lengths. There are four inequivalent Ge sites. In the first Ge site, Ge is bonded in a 9-coordinate geometry to six Tb, two In, and one Ge atom. The Ge–Ge bond length is 2.61 Å. In the second Ge site, Ge is bonded in a 9-coordinate geometry to six Tb, one Rh, one In, and one Ge atom. The Ge–Ge bond length is 2.66 Å. In the third Ge site, Ge is bonded in a 9-coordinate geometry to seven Tb, one In, and one Ge atom. In the fourth Ge site, Ge is bonded in a 9-coordinate geometry to five Tb, three equivalent Rh, and one Ge atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on DySnRh by Materials Project

DyRhSn crystallizes in the hexagonal P-62m space group. The structure is three-dimensional. Dy is bonded in a 11-coordinate geometry to five Rh and six equivalent Sn atoms. There are four shorter (3.00 Å) and one longer (3.10 Å) Dy–Rh bond lengths. There are two shorter (3.17 Å) and four longer (3.33 Å) Dy–Sn bond lengths. There are two inequivalent Rh sites. In the first Rh site, Rh is bonded in a 9-coordinate geometry to three equivalent Dy and six equivalent Sn atoms. All Rh–Sn bond lengths are 2.75 Å. In the second Rh site, Rh is bonded in a 9-coordinate geometry to six equivalent Dy and three equivalent Sn atoms. All Rh–Sn bond lengths are 2.85 Å. Sn is bonded in a 10-coordinate geometry to six equivalent Dy and four Rh atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ErBiRh by Materials Project

ErRhBi crystallizes in the hexagonal P-62m space group. The structure is three-dimensional. Er is bonded in a 11-coordinate geometry to five Rh and six equivalent Bi atoms. There are one shorter (3.06 Å) and four longer (3.07 Å) Er–Rh bond lengths. There are two shorter (3.24 Å) and four longer (3.35 Å) Er–Bi bond lengths. There are two inequivalent Rh sites. In the first Rh site, Rh is bonded in a 9-coordinate geometry to three equivalent Er and six equivalent Bi atoms. All Rh–Bi bond lengths are 2.84 Å. In the second Rh site, Rh is bonded in a 9-coordinate geometry to six equivalent Er and three equivalent Bi atoms. All Rh–Bi bond lengths are 2.85 Å. Bi is bonded in a 10-coordinate geometry to six equivalent Er and four Rh atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TbSnRh by Materials Project

TbRhSn crystallizes in the hexagonal P-62m space group. The structure is three-dimensional. Tb is bonded in a 11-coordinate geometry to five Rh and six equivalent Sn atoms. There are four shorter (3.01 Å) and one longer (3.10 Å) Tb–Rh bond lengths. There are two shorter (3.18 Å) and four longer (3.33 Å) Tb–Sn bond lengths. There are two inequivalent Rh sites. In the first Rh site, Rh is bonded in a 9-coordinate geometry to three equivalent Tb and six equivalent Sn atoms. All Rh–Sn bond lengths are 2.76 Å. In the second Rh site, Rh is bonded in a 9-coordinate geometry to six equivalent Tb and three equivalent Sn atoms. All Rh–Sn bond lengths are 2.85 Å. Sn is bonded in a 10-coordinate geometry to six equivalent Tb and four Rh atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Bi12Rh3Cl2 by Materials Project

(RhBi4)3Cl2 crystallizes in the orthorhombic Fddd space group. The structure is three-dimensional and consists of sixteen hydrochloric acid molecules and one RhBi4 framework. In the RhBi4 framework, there are two inequivalent Rh sites. In the first Rh site, Rh is bonded in a body-centered cubic geometry to eight Bi atoms. There are a spread of Rh–Bi bond distances ranging from 2.84–2.96 Å. In the second Rh site, Rh is bonded in a 8-coordinate geometry to eight Bi atoms. There are four shorter (2.85 Å) and four longer (2.87 Å) Rh–Bi bond lengths. There are three inequivalent Bi sites. In the first Bi site, Bi is bonded in a distorted water-like geometry to two Rh atoms. In the second Bi site, Bi is bonded in a distorted water-like geometry to two Rh atoms. In the third Bi site, Bi is bonded in a distorted water-like geometry to two equivalent Rh atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on YSi2Rh3 by Materials Project

YRh3Si2 crystallizes in the orthorhombic Imma space group. The structure is three-dimensional. Y is bonded in a 8-coordinate geometry to two equivalent Y, twelve Rh, and six equivalent Si atoms. Both Y–Y bond lengths are 3.62 Å. There are a spread of Y–Rh bond distances ranging from 3.09–3.55 Å. There are a spread of Y–Si bond distances ranging from 3.16–3.30 Å. There are two inequivalent Rh sites. In the first Rh site, Rh is bonded in a 12-coordinate geometry to four equivalent Y and four equivalent Si atoms. All Rh–Si bond lengths are 2.46 Å. In the second Rh site, Rh is bonded in a 4-coordinate geometry to four equivalent Y and four equivalent Si atoms. There are two shorter (2.41 Å) and two longer (2.44 Å) Rh–Si bond lengths. Si is bonded in a 6-coordinate geometry to three equivalent Y and six Rh atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HfSnRh by Materials Project

HfRhSn crystallizes in the hexagonal P-62m space group. The structure is three-dimensional. Hf is bonded in a 11-coordinate geometry to five Rh and six equivalent Sn atoms. There are four shorter (2.90 Å) and one longer (2.94 Å) Hf–Rh bond lengths. There are two shorter (3.07 Å) and four longer (3.16 Å) Hf–Sn bond lengths. There are two inequivalent Rh sites. In the first Rh site, Rh is bonded in a 9-coordinate geometry to three equivalent Hf and six equivalent Sn atoms. All Rh–Sn bond lengths are 2.69 Å. In the second Rh site, Rh is bonded in a 9-coordinate geometry to six equivalent Hf and three equivalent Sn atoms. All Rh–Sn bond lengths are 2.74 Å. Sn is bonded in a 10-coordinate geometry to six equivalent Hf and four Rh atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ThAlRh by Materials Project

ThRhAl crystallizes in the hexagonal P-62m space group. The structure is three-dimensional. Th is bonded in a 5-coordinate geometry to five Rh atoms. All Th–Rh bond lengths are 3.01 Å. There are two inequivalent Rh sites. In the first Rh site, Rh is bonded in a 9-coordinate geometry to three equivalent Th and six equivalent Al atoms. All Rh–Al bond lengths are 2.67 Å. In the second Rh site, Rh is bonded in a 9-coordinate geometry to six equivalent Th and three equivalent Al atoms. All Rh–Al bond lengths are 2.84 Å. Al is bonded in a 4-coordinate geometry to four Rh atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Dy4Ge6Rh7 by Materials Project

Dy4Rh7Ge6 crystallizes in the cubic Im-3m space group. The structure is three-dimensional. Dy is bonded to six equivalent Rh and six equivalent Ge atoms to form DyGe6Rh6 cuboctahedra that share corners with twelve equivalent DyGe6Rh6 cuboctahedra, faces with six equivalent DyGe6Rh6 cuboctahedra, and faces with two equivalent RhGe6 octahedra. All Dy–Rh bond lengths are 2.98 Å. All Dy–Ge bond lengths are 3.03 Å. There are two inequivalent Rh sites. In the first Rh site, Rh is bonded to six equivalent Ge atoms to form RhGe6 octahedra that share faces with eight equivalent DyGe6Rh6 cuboctahedra. All Rh–Ge bond lengths are 2.70 Å. In the second Rh site, Rh is bonded in a 8-coordinate geometry to four equivalent Dy and four equivalent Ge atoms. All Rh–Ge bond lengths are 2.59 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Dy and five Rh atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ZrSnRh by Materials Project

RhZrSn crystallizes in the hexagonal P-62m space group. The structure is three-dimensional. Zr is bonded in a 11-coordinate geometry to five Rh and six equivalent Sn atoms. There are four shorter (2.92 Å) and one longer (2.95 Å) Zr–Rh bond lengths. There are two shorter (3.09 Å) and four longer (3.18 Å) Zr–Sn bond lengths. There are two inequivalent Rh sites. In the first Rh site, Rh is bonded in a 9-coordinate geometry to three equivalent Zr and six equivalent Sn atoms. All Rh–Sn bond lengths are 2.70 Å. In the second Rh site, Rh is bonded in a 9-coordinate geometry to six equivalent Zr and three equivalent Sn atoms. All Rh–Sn bond lengths are 2.75 Å. Sn is bonded in a 10-coordinate geometry to six equivalent Zr and four Rh atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HfGaRh by Materials Project

HfRhGa crystallizes in the trigonal P31m space group. The structure is three-dimensional. Hf is bonded in a 11-coordinate geometry to five Rh and six equivalent Ga atoms. There are four shorter (2.79 Å) and one longer (2.86 Å) Hf–Rh bond lengths. There are a spread of Hf–Ga bond distances ranging from 2.94–3.03 Å. There are two inequivalent Rh sites. In the first Rh site, Rh is bonded in a 9-coordinate geometry to three equivalent Hf and six equivalent Ga atoms. There are three shorter (2.59 Å) and three longer (2.60 Å) Rh–Ga bond lengths. In the second Rh site, Rh is bonded in a 9-coordinate geometry to six equivalent Hf and three equivalent Ga atoms. All Rh–Ga bond lengths are 2.68 Å. Ga is bonded in a 10-coordinate geometry to six equivalent Hf and four Rh atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Facile Synthesis of Rhodium‐Based Nanocrystals in a Metastable Phase and Evaluation of Their Thermal and Catalytic Properties

Abstract Controlling the polymorphism of metal nanocrystals is a promising strategy for enhancing properties and discovering new phenomena. However, previous studies on Rh nanocrystals have focused on their thermodynamically stable face‐centered‐cubic (fcc) phase. Herein, a facile synthesis of Rh‐based nanocrystals featuring the metastable hexagonal close‐packed (hcp) phase is reported by using Ru seeds in their native hcp phase to template the deposition of Rh atoms. The success of such phase‐controlled synthesis relies on the templating effect promoted by the small lattice mismatch between Ru and Rh and the slow dropwise titration of the precursor at an elevated temperature, ensuring the layer‐by‐layer growth mode and thus the formation of a conformal hcp‐Rh shell. Faster injection rate of Rh(III) precursor leads to the formation of a rough Rh shell in the conventional fcc phase due to accelerated reaction kinetics. Considering both thermodynamic and kinetic aspects of this system, the hcp‐Rh phase is favored when the low surface energy from smooth overlayers balances the high bulk energy of the metastable phase, achieved through tight control of reaction rates and deposition patterns. These Ru hcp @Rh hcp core–shell nanocrystals demonstrate thermal stability up to 400 °C, while exhibiting higher catalytic activity toward ethanol oxidation reaction compared to Ru hcp @Rh fcc counterparts.

Nguyen, Quynh N.↗
DOE OSTI2024

Hydrogen activation by rhodium under the cover of a copper oxide thin film

Here, the activation of reactants by catalytically active metal sites at metal-oxide interfaces is important for understanding the effect of metal-support interactions on nanoparticle catalysts and for tuning activity and selectivity. Using a combined experimental and theoretical approach, we studied the activation of H 2 and the effect of CO poisoning on isolated Rh atoms completely or partially covered by a copper oxide (Cu 2 O) thin film. Temperature-programmed desorption (TPD) experiments conducted in ultra-high vacuum (UHV) show that neither a partially nor a fully oxidized Cu 2 O layer grown on a Rh/Cu(111) single-atom alloy can activate hydrogen in UHV. However, in situ ambient pressure X-ray photoelectron spectroscopy (AP-XPS) experiments performed at elevated H 2 pressures reveal that Rh significantly accelerates the reduction of these Cu 2 O thin films by hydrogen. Remarkably, the fastest reduction rate is observed for the fully oxidized sample with all Rh sites covered by Cu 2 O. Both TPD and AP-XPS data demonstrate that these covered Rh sites are inaccessible to CO, indicating that Rh under Cu 2 O is active for H 2 dissociation but cannot be poisoned by CO. In contrast, an incomplete oxide film leaves some of the Rh sites exposed and accessible to CO, and hence prone to CO poisoning. Density functional theory calculations demonstrate that unlike many reactions in which hydrogen activation is rate limiting, the rate-determining step in the dissociation of H 2 on thin-film Cu 2 O with Rh underneath is the adsorption of H 2 on the buried Rh site, and once adsorbed, the dissociation of H 2 is barrierless. These calculations also explain why H 2 can only be activated at higher pressures. Together, these results highlight how different the reactivity of atomically dispersed Rh in Cu can be depending on its accessibility through the oxide layer, providing a way to engineer Rh sites that are active for hydrogen activation but resilient to CO poisoning.

36 MATERIALS SCIENCE↗
DOE OSTI2024

The evolution of model Rh/Fe 3 O 4 (001) catalysts in hydrogen environments

Single metal atoms dispersed on oxides are a new emerging class of catalysts owing to their unique electronic and chemical properties. Here, in this study, we have prepared a series of model single-atom catalysts possessing well-characterized Rh sites that include Rh adatoms (Rh ad ), mixed surface layers with octahedrally-coordinated Rh (Rh oct ), as well as metallic Rh clusters and nanoparticles (Rh met ) on Fe 3 O 4 (001). Using X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM), we investigated the activity of such model systems towards H2 and their stability in reducing environments. Our results show that the atomically dispersed Rhad and Rhoct species do not activate H 2 , which would result in the formation of surface hydroxyls on Fe 3 O 4 (001). In contrast, the presence of Rh met in H 2 results in the formation of hydroxyls and subsequent etching of the Fe 3 O 4 (001) at higher temperatures (≥ 500 K) due to water formation via the Mars-van Krevelen mechanism. Additionally, such surface etching leads to the release of the Rh oct from the surface lattice and their sintering to Rh met . To bridge the material gap between the surface science models and high surface area catalysts, we perform parallel studies on powder Rh/Fe 3 O 4 catalysts. The XPS characterization shows remarkable similarities between these systems. Further, our surface science studies provide an atomistic picture of the behavior of high surface area catalysts in the H 2 atmosphere.

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

Thermodynamics and dehydration/hydration behaviors of Na-sulfate, -borate, and -bicarbonate minerals

Here, detailed thermal experiments using relative humidity- (RH) and temperature-controlled X-ray diffraction (XRD) and H 2 O adsorption/desorption measurements were applied to understand the dehydration/hydration behaviors of thenardite/mirabilite (Na 2 SO 4 /Na 2 SO 4 ·10H 2 O), tincalconite/borax (Na 2 B 4 O 7 ·5H 2 O/Na 2 B 4 O 7 ·10H 2 O), nahcolite (NaHCO 3 ), and qilianshanite (NaH 4 (BO 3 ) (CO 3 )·2H 2 O or NaHCO 3 ·H 3 BO 3 ·2H 2 O). The thermal behaviors of thenardite/mirabilite and tincalconite/borax were evaluated at room temperature as a function of RH. Hydration of thenardite to mirabilite is very sluggish and does not begin until at least 85 % RH, whereas dehydration of mirabilite to thenardite occurs at ~76 % RH. The reactions are accessible in the solid state and were not completely reversible on the time scale of these measurements. Qilianshanite appears stable under room conditions, as long as the RH is >20 %, supported by 2.5 months of observation during exposure to room air of known RH. Qilianshanite persists metastably for at least two days when exposed to both wet and 0% RH atmospheres at room temperature, observed during environment-controlled XRD. Below 20 % RH, qilianshanite sluggishly reacts to form tincalconite and nahcolite. When heated, qilianshanite broke down at 70 °C based on XRD results, and thermogravimetric analysis (TGA) confirmed a dehydration temperature of ~75 °C. Tincalconite hydrated to borax at 80 % RH, and dehydration from borax to tincalconite occurred at 40–50 % RH, illustrating the effective reversibility of the reaction under room conditions. The minor phase nahcolite originally in qilianshanite remained in the residue of decomposed qilianshanite after heating to 125 °C, demonstrated by continuous XRD measurements, whereas nahcolite was largely dehydrated when heated to ~100 °C during TGA. The difference can be attributed to the slower reaction kinetics in the environmental XRD. These results shed considerable light on the behavior of these minerals in the environment, particularly in evaporite deposits in Antarctica, where all of these minerals are reacting with the atmosphere on a diurnal-to-seasonal basis.

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

Bottom-up evolution of perovskite clusters into high-activity rhodium nanoparticles toward alkaline hydrogen evolution

Self-reconstruction has been considered an efficient means to prepare efficient electrocatalysts in various energy transformation process for bond activation and breaking. However, developing nano-sized electrocatalysts through complete in-situ reconstruction with improved activity remains challenging. Herein, we report a bottom-up evolution route of electrochemically reducing Cs 3 Rh 2 I 9 halide-perovskite clusters on N-doped carbon to prepare ultrafine Rh nanoparticles (~2.2 nm) with large lattice spacings and grain boundaries. Various in-situ and ex-situ characterizations including electrochemical quartz crystal microbalance experiments elucidate the Cs and I extraction and Rh reduction during the electrochemical reduction. These Rh nanoparticles from Cs 3 Rh 2 I 9 clusters show significantly enhanced mass and area activity toward hydrogen evolution reaction in both alkaline and chlor-alkali electrolyte, superior to liquid-reduced Rh nanoparticles as well as bulk Cs 3 Rh 2 I 9 -derived Rh via top-down electro-reduction transformation. Theoretical calculations demonstrate water activation could be boosted on Cs 3 Rh 2 I 9 clusters-derived Rh nanoparticles enriched with multiply sites, thus smoothing alkaline hydrogen evolution.

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

Materials Data on Te2Rh3 by Materials Project

Rh3Te2 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are two inequivalent Rh sites. In the first Rh site, Rh is bonded in a 5-coordinate geometry to five Te atoms. There are one shorter (2.66 Å) and four longer (2.75 Å) Rh–Te bond lengths. In the second Rh site, Rh is bonded in a 5-coordinate geometry to five Te atoms. There are three shorter (2.66 Å) and two longer (2.80 Å) Rh–Te bond lengths. There are two inequivalent Te sites. In the first Te site, Te is bonded in a body-centered cubic geometry to eight Rh atoms. In the second Te site, Te is bonded in a 7-coordinate geometry to seven Rh atoms.

36 MATERIALS SCIENCE↗