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At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Sb2H12Pd(CCl)4 by Materials Project

PdSb2H12(CCl)4 crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of two PdSb2H12(CCl)4 clusters. Pd2+ is bonded in a distorted L-shaped geometry to one Sb3+ and two Cl1- atoms. The Pd–Sb bond length is 2.55 Å. Both Pd–Cl bond lengths are 2.40 Å. There are four inequivalent C4- sites. In the first C4- site, C4- is bonded in a distorted trigonal non-coplanar geometry to one Sb3+ and three H1+ atoms. The C–Sb bond length is 2.15 Å. There is one shorter (1.09 Å) and two longer (1.10 Å) C–H bond length. In the second C4- site, C4- is bonded in a distorted trigonal non-coplanar geometry to one Sb3+ and three H1+ atoms. The C–Sb bond length is 2.15 Å. There is two shorter (1.09 Å) and one longer (1.10 Å) C–H bond length. In the third C4- site, C4- is bonded in a distorted trigonal non-coplanar geometry to one Sb3+ and three H1+ atoms. The C–Sb bond length is 2.15 Å. There is one shorter (1.09 Å) and two longer (1.10 Å) C–H bond length. In the fourth C4- site, C4- is bonded in a distorted trigonal non-coplanar geometry to one Sb3+ and three H1+ atoms. The C–Sb bond length is 2.14 Å. There is one shorter (1.09 Å) and two longer (1.10 Å) C–H bond length. There are two inequivalent Sb3+ sites. In the first Sb3+ site, Sb3+ is bonded in a 5-coordinate geometry to one Pd2+, two C4-, and two Cl1- atoms. There are one shorter (2.43 Å) and one longer (3.01 Å) Sb–Cl bond lengths. In the second Sb3+ site, Sb3+ is bonded in a 5-coordinate geometry to two C4- and two Cl1- atoms. There are one shorter (2.42 Å) and one longer (3.08 Å) Sb–Cl bond lengths. There are twelve inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the seventh H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the eighth H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the ninth H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the tenth H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the eleventh H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the twelfth H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. There are four inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a single-bond geometry to one Sb3+ atom. In the second Cl1- site, Cl1- is bonded in a single-bond geometry to one Sb3+ atom. In the third Cl1- site, Cl1- is bonded in a distorted water-like geometry to one Pd2+ and one Sb3+ atom. In the fourth Cl1- site, Cl1- is bonded in a 1-coordinate geometry to one Pd2+ and one Sb3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Single-atom catalysts with anionic metal centers: promising electrocatalysts for the oxygen reduction reaction and beyond

Ongoing efforts to develop single-atom catalysts (SACs) for the oxygen reduction reaction (ORR) typically focus on SACs with cationic metal centers, while SACs with anionic metal centers (anionic SACs) have been generally neglected. However, anionic SACs may offer excellent active sites for ORR, since anionic metal centers could facilitate the activation of O2 by back donating electrons to the antibonding orbitals of O2. In this work, we propose a simple guideline for designing anionic SACs: the metal centers should have larger electronegativity than the surrounding atoms in the substrate on which the metal atoms are supported. By means of density functional theory (DFT) simulations, we identified 13 anionic metal centers (Co, Ni, Cu, Ru, Rh, Pd, Ag, Re, Os, Ir, Pt, Au, and Hg) dispersed on pristine or defective antimonene substrates as new anionic SACs, among which anionic Au and Co metal centers exhibit limiting potentials comparable to, or even better than, conventional Pt-based catalysts towards ORR. We also found that anionic Os and Re metal centers on the defective antimonene can electrochemically catalyze the nitrogen reduction reaction (NRR) with a limiting potential close to that of stepped Ru(0001). Overall, our work shows promise towards the rational design of anionic SACs and their utility for applications as electrocatalysts for ORR and other important electrochemical reactions.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Monolayer Support Control and Precise Colloidal Nanocrystals Demonstrate Metal-Support Interactions in Heterogeneous Catalysts

We report that electronic and geometric interactions between active and support phases are critical in determining the activity of heterogeneous catalysts, but metal-support interactions are challenging to study. Here, it is demonstrated how the combination of the monolayer-controlled formation using atomic layer deposition (ALD) and colloidal nanocrystal synthesis methods leads to catalysts with sub-nanometer precision of active and support phases, thus allowing for the study of the metal-support inter-actions in detail. The use of this approach in developing a fundamental understanding of support effects in Pd-catalyzed methane combustion is demonstrated. Uniform Pd nanocrystals are deposited onto Al2O 3 /SiO 2 spherical supports prepared with control over morphology and Al 2 O 3 layer thicknesses ranging from sub-monolayer to a ≈4 nm thick uniform coating. Dramatic changes in catalytic activity depending on the coverage and structure of Al 2 O 3 situated at the Pd/Al 2 O 3 interface are observed, with even a single monolayer of alumina contributing an order of magnitude increase in reaction rate. By building the Pd/Al 2 O 3 interface up layer-by-layer and using uniform Pd nanocrystals, this work demonstrates the importance of controlled and tunable materials in determining metal-support interactions and catalyst activity.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on H16PdC4S4(N4Cl)2 by Materials Project

PdC4H16(N2S)4Cl2 crystallizes in the monoclinic C2/c space group. The structure is zero-dimensional and consists of eight hydrochloric acid molecules and four PdC4H16(N2S)4 clusters. In each PdC4H16(N2S)4 cluster, Pd2+ is bonded in a square co-planar geometry to four S2- atoms. There are two shorter (2.37 Å) and two longer (2.38 Å) Pd–S bond lengths. There are two inequivalent C4+ sites. In the first C4+ site, C4+ is bonded in a distorted trigonal planar geometry to two N3- and one S2- atom. There is one shorter (1.33 Å) and one longer (1.34 Å) C–N bond length. The C–S bond length is 1.74 Å. In the second C4+ site, C4+ is bonded in a distorted trigonal planar geometry to two N3- and one S2- atom. There is one shorter (1.33 Å) and one longer (1.34 Å) C–N bond length. The C–S bond length is 1.74 Å. There are four inequivalent N3- sites. In the first N3- site, N3- is bonded in a trigonal planar geometry to one C4+ and two H1+ atoms. There is one shorter (1.02 Å) and one longer (1.03 Å) N–H bond length. In the second N3- site, N3- is bonded in a trigonal planar geometry to one C4+ and two H1+ atoms. Both N–H bond lengths are 1.02 Å. In the third N3- site, N3- is bonded in a trigonal planar geometry to one C4+ and two H1+ atoms. There is one shorter (1.02 Å) and one longer (1.03 Å) N–H bond length. In the fourth N3- site, N3- is bonded in a trigonal planar geometry to one C4+ and two H1+ atoms. Both N–H bond lengths are 1.02 Å. There are eight inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the seventh H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the eighth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a water-like geometry to one Pd2+ and one C4+ atom. In the second S2- site, S2- is bonded in a water-like geometry to one Pd2+ and one C4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on H16PdC4S4(N5O3)2 by Materials Project

PdC4H16(N2S)4(NO3)2 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of two nitric acid molecules and one PdC4H16(N2S)4 cluster. In the PdC4H16(N2S)4 cluster, Pd2+ is bonded in a square co-planar geometry to four S2- atoms. There are two shorter (2.35 Å) and two longer (2.37 Å) Pd–S bond lengths. There are two inequivalent C4+ sites. In the first C4+ site, C4+ is bonded in a distorted trigonal planar geometry to two N+1.40- and one S2- atom. There is one shorter (1.32 Å) and one longer (1.33 Å) C–N bond length. The C–S bond length is 1.76 Å. In the second C4+ site, C4+ is bonded in a distorted trigonal planar geometry to two N+1.40- and one S2- atom. There is one shorter (1.33 Å) and one longer (1.34 Å) C–N bond length. The C–S bond length is 1.72 Å. There are four inequivalent N+1.40- sites. In the first N+1.40- site, N+1.40- is bonded in a trigonal planar geometry to one C4+ and two H1+ atoms. Both N–H bond lengths are 1.03 Å. In the second N+1.40- site, N+1.40- is bonded in a trigonal planar geometry to one C4+ and two H1+ atoms. There is one shorter (1.02 Å) and one longer (1.03 Å) N–H bond length. In the third N+1.40- site, N+1.40- is bonded in a trigonal planar geometry to one C4+ and two H1+ atoms. Both N–H bond lengths are 1.02 Å. In the fourth N+1.40- site, N+1.40- is bonded in a trigonal planar geometry to one C4+ and two H1+ atoms. There is one shorter (1.01 Å) and one longer (1.02 Å) N–H bond length. There are eight inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one N+1.40- atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one N+1.40- atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one N+1.40- atom. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one N+1.40- atom. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one N+1.40- atom. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one N+1.40- atom. In the seventh H1+ site, H1+ is bonded in a single-bond geometry to one N+1.40- atom. In the eighth H1+ site, H1+ is bonded in a single-bond geometry to one N+1.40- atom. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a water-like geometry to one Pd2+ and one C4+ atom. In the second S2- site, S2- is bonded in a water-like geometry to one Pd2+ and one C4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Selective activation of methane C–H bond in the presence of methanol

Direct methane to methanol (MTM) conversion over heterogeneous catalysts is a promising route for valorization of methane. The methane C-H bond activation is considered as the key step of the MTM and is the focus of considerable research activity. However, the formed methanol typically suffers from overoxidation largely due to the cleavage of a methanol C-H bond, whose bond dissociation energy is ca. 0.5 eV lower than that of the methane C-H bond, which usually translates to a transition state energy of the methanol C-H bond cleavage that is ca. 0.55 eV lower than that of methane whenever the reactions proceed through a radical mechanism. Furthermore, we propose a general approach for decreasing the transition state energy difference between the CH 4 and CH 3 OH C-H bond dissociation. When a metal-oxide supported cationic transition metal atom and a neighboring oxygen on the oxide surface serve as the active site, the transition state energy difference through a surface-stabilized pathway can be noticeably narrowed as compared with that of a radical pathway. For Ir, Pt and Rh-doped anatase TiO 2 (101), the CH 4 C-H bond activation can be preferred over that of CH 3 OH at significant methanol mole fraction. Also, for PdAu alloys containing adsorbed oxygen and positively charged Pd, calculations suggest in agreement with recent experiments (Science 367 (6474), 193-197) that the CH 4 C-H bond can be selectively activated in the presence of CH 3 OH.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1995

Quaternary borocarbides: New class of intermetallic superconductors

Our recent discovery of superconductivity (SC) in the four-element multiphase Y-Ni-B-C system at an elevated temperature (TC approximately 12 K) has opened up great possibilities of identifying new superconducting materials and generating new physics. Superconductivity with Tc (greater than 20 K) higher than that known so far in bulk intermetallics has been observed in multiphase Y-Pd-B-C and Th-Pd-B-C systems and a family of single phase materials RENi2B2C (RE= Y, rare earth) have been found. Our investigations show YNi2B2C to be a strong coupling hard type-II SC. HC2(T) exhibits an unconventional temperature dependence. Specific heat and magnetization studies reveal coexistence of SC and magnetism in RNi2B2C (R = Ho, Er, Tm) with magnetic ordering temperatures (Tc approximately 8 K, 10.5 K, 11 K and Tm approximately 5 K, approximately 7K, approximately 4 K respectively) that are remarkably higher than those in known magnetic superconductors . Mu-SR studies suggest the possibility of Ni atoms carrying a moment in TmNi2B2C. Resistivity results suggests a double re-entrant transition (SC-normal-SC) in HoNi2B2C. RENi2B2C (RE = Ce, Nd, Gd) do not show SC down to 4.2 K. The Nd- and Gd-compounds order magnetically at approximately 4.5 K and approximately 19.5 K, respectively. Two SC transitions are observed in Y-Pd-B-C (Tc approximately 22 K, approximately 10 K) and in Th-Pd-B-C (Tc approximately 20 K, approximately 14 K) systems, which indicate that there are at least two structures which support SC in these borocarbides. In our multiphase ThNi2B2C we observe SC at approximately 6 K. No SC was seen in multiphase UNi2B2C, UPd2B2C, UOs2Ge2C and UPd5B3C(0.35) down to 4.2 K. Tc in YNi2B2C is depressed by substitutions (Gd, Th and U at Y-sites and Fe, Co at Ni-sites).

Nagarajan, R.↗
DOE OSTI2020

Materials Data on PdC4S4(IN4)2 by Materials Project

PdC4S4(N4I)2 crystallizes in the monoclinic C2/c space group. The structure is one-dimensional and consists of two PdC4S4(N4I)2 ribbons oriented in the (-1, 0, 1) direction. Pd2+ is bonded in a distorted octahedral geometry to two equivalent N1- and four S2- atoms. Both Pd–N bond lengths are 2.13 Å. There are two shorter (2.39 Å) and two longer (2.41 Å) Pd–S bond lengths. There are two inequivalent C4+ sites. In the first C4+ site, C4+ is bonded in a 1-coordinate geometry to two N1- and one S2- atom. Both C–N bond lengths are 1.37 Å. The C–S bond length is 1.62 Å. In the second C4+ site, C4+ is bonded in a distorted trigonal planar geometry to two N1- and one S2- atom. There is one shorter (1.32 Å) and one longer (1.34 Å) C–N bond length. The C–S bond length is 1.80 Å. There are four inequivalent N1- sites. In the first N1- site, N1- is bonded in a distorted single-bond geometry to one C4+ and one S2- atom. The N–S bond length is 2.87 Å. In the second N1- site, N1- is bonded in a distorted single-bond geometry to one C4+ atom. In the third N1- site, N1- is bonded in a 2-coordinate geometry to one Pd2+, one C4+, and one I1- atom. The N–I bond length is 2.32 Å. In the fourth N1- site, N1- is bonded in a distorted bent 120 degrees geometry to one C4+ and one I1- atom. The N–I bond length is 2.06 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a distorted water-like geometry to one Pd2+ and one C4+ atom. In the second S2- site, S2- is bonded in a 3-coordinate geometry to one Pd2+, one C4+, and one N1- atom. I1- is bonded in a 2-coordinate geometry to two N1- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Structure of HhaI endonuclease with cognate DNA at an atomic resolution of 1.0 Å

HhaI, a Type II restriction endonuclease, recognizes the symmetric sequence 5'-GCG↓C-3' in duplex DNA and cleaves (‘↓’) to produce fragments with 2-base, 3'-overhangs. We determined the structure of HhaI in complex with cognate DNA at an ultra-high atomic resolution of 1.0 Å. Most restriction enzymes act as dimers with two catalytic sites, and cleave the two strands of duplex DNA simultaneously, in a single binding event. HhaI, in contrast, acts as a monomer with only one catalytic site, and cleaves the DNA strands sequentially, one after the other. HhaI comprises three domains, each consisting of a mixed five-stranded β sheet with a defined function. The first domain contains the catalytic-site; the second contains residues for sequence recognition; and the third contributes to non-specific DNA binding. The active-site belongs to the ‘PD-D/EXK’ superfamily of nucleases and contains the motif SD-X11-EAK. The first two domains are similar in structure to two other monomeric restriction enzymes, HinP1I (G↓CGC) and MspI (C↓CGG), which produce fragments with 5'-overhangs. The third domain, present only in HhaI, shifts the positions of the recognition residues relative to the catalytic site enabling this enzyme to cleave the recognition sequence at a different position. The structure of M.HhaI, the biological methyltransferase partner of HhaI, was determined earlier. Together, these two structures represent the first natural pair of restriction-modification enzymes to be characterized in atomic detail.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Materials Data on Pd2S9N4 by Materials Project

Pd2N4S9 crystallizes in the trigonal R-3 space group. The structure is zero-dimensional and consists of eighteen Pd2N4S9 clusters. there are two inequivalent Pd3+ sites. In the first Pd3+ site, Pd3+ is bonded in a rectangular see-saw-like geometry to four S2- atoms. There are a spread of Pd–S bond distances ranging from 2.30–2.39 Å. In the second Pd3+ site, Pd3+ is bonded in a rectangular see-saw-like geometry to four S2- atoms. There are a spread of Pd–S bond distances ranging from 2.31–2.39 Å. There are four inequivalent N3+ sites. In the first N3+ site, N3+ is bonded in a bent 120 degrees geometry to two S2- atoms. There is one shorter (1.57 Å) and one longer (1.63 Å) N–S bond length. In the second N3+ site, N3+ is bonded in a bent 120 degrees geometry to two S2- atoms. There is one shorter (1.58 Å) and one longer (1.64 Å) N–S bond length. In the third N3+ site, N3+ is bonded in a bent 120 degrees geometry to two S2- atoms. There is one shorter (1.57 Å) and one longer (1.63 Å) N–S bond length. In the fourth N3+ site, N3+ is bonded in a bent 120 degrees geometry to two S2- atoms. There is one shorter (1.58 Å) and one longer (1.64 Å) N–S bond length. There are nine inequivalent S2- sites. In the first S2- site, S2- is bonded in a 1-coordinate geometry to two Pd3+ and one N3+ atom. In the second S2- site, S2- is bonded in a 1-coordinate geometry to two Pd3+ and one N3+ atom. In the third S2- site, S2- is bonded in a distorted single-bond geometry to one N3+ and one S2- atom. The S–S bond length is 2.03 Å. In the fourth S2- site, S2- is bonded in a distorted water-like geometry to one Pd3+ and one N3+ atom. In the fifth S2- site, S2- is bonded in a water-like geometry to one Pd3+ and one N3+ atom. In the sixth S2- site, S2- is bonded in a distorted single-bond geometry to one N3+ and one S2- atom. The S–S bond length is 2.03 Å. In the seventh S2- site, S2- is bonded in a distorted water-like geometry to one Pd3+ and one S2- atom. In the eighth S2- site, S2- is bonded in a bent 120 degrees geometry to two N3+ atoms. In the ninth S2- site, S2- is bonded in a distorted water-like geometry to one Pd3+ and one S2- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na2Pd(S4O13)2 by Materials Project

Na2Pd(S4O13)2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Na1+ is bonded to seven O2- atoms to form distorted NaO7 pentagonal bipyramids that share corners with seven SO4 tetrahedra. There are a spread of Na–O bond distances ranging from 2.45–2.72 Å. Pd2+ is bonded in a square co-planar geometry to four O2- atoms. There are two shorter (2.04 Å) and two longer (2.05 Å) Pd–O bond lengths. There are four inequivalent S6+ sites. In the first S6+ site, S6+ is bonded to four O2- atoms to form SO4 tetrahedra that share corners with two equivalent NaO7 pentagonal bipyramids and a cornercorner with one SO4 tetrahedra. There are a spread of S–O bond distances ranging from 1.43–1.76 Å. In the second S6+ site, S6+ is bonded to four O2- atoms to form SO4 tetrahedra that share a cornercorner with one NaO7 pentagonal bipyramid and corners with two SO4 tetrahedra. There are a spread of S–O bond distances ranging from 1.42–1.69 Å. In the third S6+ site, S6+ is bonded to four O2- atoms to form SO4 tetrahedra that share corners with two equivalent NaO7 pentagonal bipyramids and corners with two SO4 tetrahedra. There are a spread of S–O bond distances ranging from 1.43–1.63 Å. In the fourth S6+ site, S6+ is bonded to four O2- atoms to form SO4 tetrahedra that share corners with two equivalent NaO7 pentagonal bipyramids and a cornercorner with one SO4 tetrahedra. There are a spread of S–O bond distances ranging from 1.43–1.75 Å. There are thirteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 120 degrees geometry to two S6+ atoms. In the second O2- site, O2- is bonded in a distorted single-bond geometry to one Na1+ and one S6+ atom. In the third O2- site, O2- is bonded in a bent 120 degrees geometry to two S6+ atoms. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to one Na1+ and one S6+ atom. In the fifth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Pd2+ and one S6+ atom. In the sixth O2- site, O2- is bonded in a single-bond geometry to one S6+ atom. In the seventh O2- site, O2- is bonded in a bent 120 degrees geometry to two S6+ atoms. In the eighth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Na1+ and one S6+ atom. In the ninth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Na1+ and one S6+ atom. In the tenth O2- site, O2- is bonded in a distorted single-bond geometry to one Na1+ and one S6+ atom. In the eleventh O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Na1+ and one S6+ atom. In the twelfth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Pd2+ and one S6+ atom. In the thirteenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Na1+ and one S6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Fleetite, Cu 2 RhIrSb 2 , a New Species of Platinum-Group Mineral from the Miass Placer Zone, Southern Urals, Russia

Fleetite, Cu 2 RhIrSb 2 , a new species of platinum-group mineral (PGM), was discovered intergrown with an Os–Ir–Ru alloy in the Miass Placer Zone (Au–PGE), southern Urals, Russia. A single grain 50 μm across was found. Osmium, ruthenium, and iridium are the main associated minerals; also present are Pt–Fe alloys, laurite, Sb-rich irarsite, Rh-rich tolovkite, kashinite, anduoite, ferronickelplatinum, heazlewoodite, PGE-bearing pentlandite and digenite, as well as micrometric inclusions of forsterite (Fo 93.7 ), chromite–magnesiochromite, and Mg-rich edenite. In reflected light, fleetite is light gray; it is opaque, isotropic, non-pleochroic, and non-bireflectant. We report reflectance values measured in air. A mean of seven point-analyses (wavelength-dispersive spectrometry) gave Cu 13.93, Ni 8.60, Fe 0.10, Ir 28.07, Rh 7.91, Ru 1.96, Sb 39.28, total 99.85 wt.%, corresponding to (Cu 1.41 Ni 0.58 Fe 0.01 ) Σ2.00 (Rh 0.49 Ni 0.36 Ru 0.12 ) Σ0.97 Ir 0.95 Sb 2.08 on the basis of six atoms per formula unit, taking into account the structural results. The calculated density is 10.83 g/cm 3 . Single-crystal X-ray studies show that fleetite is cubic, space group Fdm (#227), a = 11.6682(8) Å, V = 1588.59(19) Å 3 , and Z = 16. A least-squares refinement of X-ray powder-diffraction data gave a = 11.6575(5) Å and V = 1584.22(19) Å 3 . The strongest five reflections in the powder pattern [d in Å(I)(hkl)] are: 6.70(75)(111), 4.13(100)(220), 3.52(30)(311), 2.380(50)(422), 2.064(40)(440). Results of synchrotron micro-Laue diffraction experiments are consistent [a = 11.66(2) Å]. The crystal structure of fleetite was solved and refined to R = 0.0340 based upon 153 reflections with F o > 4σ(F o ). It is isotypic with Pd 11 Bi 2 Se 2 and best described as intermetallic, with all metal atoms in 12-fold coordination. Fleetite and other late exotic phases were formed by reaction of the associated alloy phases with a fluid phase enriched in Sb, As, and S in circulation in the cooling ophiolite source-rock. The mineral is named after Michael E. Fleet (1938–2017) in recognition of his significant contributions to the Earth Sciences.

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

High-resolution vibrational predissociation spectroscopy of I - ·H 2 O by single-mode CW infrared excitation in a 3D cryogenic ion trap

We describe the integration of a tunable, single-mode, continuous wave infrared laser into a cryogenic ion spectroscopy experiment to measure the rovibrational spectrum of the I - ∙H 2 O complex in the OH stretching region. These upper levels lie about 300 cm -1 above the dissociation threshold. The measurements are carried out by loading the ions in a radiofrequency ion trap at 10 Hz and cooling them to 5 K with pulsed He buffer gas. IR photodissociation (PD) of the I - ∙H 2 O complex is monitored by recording the I - product yield by time-of-flight mass spectrometry as a function of laser wavelength. Very narrow (Δν~75 MHz) rotational lines are observed throughout the spectrum, indicating long (ca. 2 ns) lifetimes for the excited metastable rovibrational levels. Rotational analysis of the band arising from the K”=1 to K’=2 transition of the free OH stretching fundamental yields the structure of the complex for the first time. Over 50% of the trapped ion ensemble in the trap can be photodissociated upon excitation of a single rotational line. This enables very high signal-to-noise in the PD spectrum, and is traced to a mechanism in which the ground state rotational levels are rapidly equilibrated by collisions with the buffer gas.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2020

Atomic-Scale Structure and Catalysis on Positively Charged Bimetallic Sites for Generation of H 2

In this paper, we report that a cationic bimetallic site consisting of one Pd and three Zn atoms (Pd 1 Zn 3 ) supported on ZnO (Pd 1 Zn 3 /ZnO) exhibits an extraordinarily high catalytic activity for the generation of H 2 through methanol partial oxidation (MPO) that is 2–3 orders of magnitude higher than that of a metallic Pd–Zn site on Pd–Zn nanoalloy (Pd–Zn/ZnO). Computational studies uncovered that the positively charged Pd atom of the subnanometer Pd 1 Zn 3 bimetallic site largely decreases the activation barrier for dehydrogenation of methanol as compared to a metallic Pd atom of Pd–Zn alloy, thus switching the rate-determining step of MPO from methanol dehydrogenation over a Pd–Zn alloy with high barrier to the O 2 dissociation step on a cationic Pd 1 Zn 3 site with a low barrier, which is supported by our kinetics studies. The significantly higher catalytic activity and selectivity for H 2 production over a cationic bimetallic site suggest a new approach to design bimetallic catalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Programmable Catalyst Structures via Adsorbate-Induced Adatom Assembly

The electronic structure and geometric configuration of oxide-supported metal ions are important coordination properties that can be related to catalytic activity and stability. Herein, we interrogate the coordination environment of mononuclear Pd ions supported on ceria using CO adsorption, infrared vibrational spectroscopy, and DFT modeling. We observed the 15 h continuous co-evolution of a palladium- (2167 cm -1 ) and cerium-carbonyl (2177 cm -1 ) complex by monitoring the $\nu$(CO) infrared region. The slow CO adsorption kinetics were caused by the reactive ligand exchange between an oxygen atom of the support and the CO adsorbate to yield an oxygen vacancy and adsorbed CO 2 . We hypothesize that the co-evolved cerium-carbonyl complex was formed upon CO adsorption at or adjacent to this oxygen vacancy. Our hypothesis was experimentally supported by a dramatic attenuation of the cerium carbonyl signal upon pre-adsorption of water through an apparent competitive adsorption mechanism. The attenuation was also accompanied by a 6 cm -1 redshift of the palladium carbonyl band (2161 cm -1 ) attributed to hydrogen bonding between the carbonyl and a nearby hydroxyl. Characteristic n(CO) stretch frequencies catalogued through CO adsorption onto single crystal ceria by Wöll et al.1 led us to index the cerium carbonyl to the {100} nanofacet of the polycrystalline ceria support. It follows from the observed co-evolution of the two carbonyl complexes that Pd was also adsorbed at the {100} nanofacet. Redeployment of a previously developed DFT model by Ivanova-Shor et al.2 featuring square-planar coordination of Pd2+ at the {100} nanofacet (O 4 Pd) of a Ce 21 O 42 nanoparticle model qualitatively reproduced several experimental observations.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Acetate formation on metals via CH 4 carboxylation by CO 2 : A DFT study

Here, density functional theory calculations have been performed to investigate CH 4 activation and coupling to CO 2 forming C 2 carboxylates such as acetate on the close-packed (111) or (0001) surfaces of ten mid-to-late transition and coinage metals (Co, Ni, Cu, Ru, Rh, Pd, Ag, Ir, Pt, and Au). Consistent with the literature, the activation energy (E a ) for the initial C-H bond scission in CH 4 is mild, being ca. 1 eV or less on all but the coinage metals, of which Ag exhibits the highest E a at 2.13 eV, followed by Au and Cu. E a for the CH 3 -CO 2 coupling step is 0.8 ~ 1.1 eV on Co, Ru, Rh, and Ag, 1.2 ~ 1.5 eV on Ni, Cu, Pd, and Ir, and 1.8 ~ 2.1 eV on Pt and Au. While the two E a are comparable for several metals in terms of DFT total energies, free energy analysis indicates CH 3 -CO 2 coupling to be much more rate-limiting than CH 4 activation. Overcoming it would require over 800 K even on the most active of the metals considered, Ru, which makes the formation of acetate not feasible on the monometallic metal surfaces. Instead, we propose that single atom alloys based on early transition metals doped into a host metal such as Ni(111) could be viable catalysts. The dopant sites serve to stabilize the transition state of C-C coupling while Ni sites continue to activate CH 4 , thereby significantly lowering the required temperature for acetate formation.

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

Atomic Structural Origin of the High Methanol Selectivity over In 2 O 3 –Metal Interfaces: Metal–Support Interactions and the Formation of a InO x Overlayer in Ru/In 2 O 3 Catalysts during CO 2 Hydrogenation

CO 2 hydrogenation to methanol is of great environmental and economic interest due to its potential to reduce carbon emissions and produce valuable chemicals in one single reaction. Compared with the unmodified traditional Cu/ZnO/Al 2 O 3 catalyst, an indium oxide (In 2 O 3 )-based catalyst can double the methanol selectivity from 30–50 to 60–100%. It is worth noting that over catalysts involving various active metals dispersed on indium oxide (M/In 2 O 3 , M = Pd, Ni, Au, etc.), although the methanol yield is boosted, the selectivity remains similar to that of plain In 2 O 3 despite the distinct chemical properties of the added metals. Here, to investigate the phenomena behind this behavior, we used RuO 2 /In 2 O 3 as a test catalyst. The results of ambient pressure photoelectron spectroscopy, in situ X-ray absorption fine structure, and time-resolved X-ray diffraction indicate that the structure of the RuO 2 /In 2 O 3 catalyst is highly dynamic in the presence of a reactive environment. Specifically, under CO 2 hydrogenation conditions, Ru clusters facilitate the reduction of In 2 O 3 to generate In 2 O 3–x aggregates, which encapsulate the Ru systems in a migration driven by thermodynamics. In this way, the Ru O sites for CH 4 production are blocked while creating RuO x –In 2 O 3–x interfacial sites with tunable metal–oxide interactions for selective methanol production. In an inverse oxide/metal configuration, indium oxide has properties not seen in its bulk phase that are useful for the binding and conversion of CO 2 . This work reveals the dynamic nature of In 2 O 3 -based catalysts, providing insights for a rational design of materials for the selective synthesis of methanol.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on H16PdC4S4(N4Cl)2 by Materials Project

PdC4H16(N2S)4Cl2 crystallizes in the orthorhombic Pna2_1 space group. The structure is zero-dimensional and consists of eight hydrochloric acid molecules and four PdC4H16(N2S)4 clusters. In each PdC4H16(N2S)4 cluster, Pd2+ is bonded in a rectangular see-saw-like geometry to four S2- atoms. There are two shorter (2.34 Å) and two longer (2.37 Å) Pd–S bond lengths. There are four inequivalent C4+ sites. In the first C4+ site, C4+ is bonded in a distorted trigonal planar geometry to two N3- and one S2- atom. There is one shorter (1.33 Å) and one longer (1.34 Å) C–N bond length. The C–S bond length is 1.73 Å. In the second C4+ site, C4+ is bonded in a distorted trigonal planar geometry to two N3- and one S2- atom. There is one shorter (1.33 Å) and one longer (1.35 Å) C–N bond length. The C–S bond length is 1.72 Å. In the third C4+ site, C4+ is bonded in a distorted trigonal planar geometry to two N3- and one S2- atom. There is one shorter (1.33 Å) and one longer (1.34 Å) C–N bond length. The C–S bond length is 1.73 Å. In the fourth C4+ site, C4+ is bonded in a distorted trigonal planar geometry to two N3- and one S2- atom. There is one shorter (1.33 Å) and one longer (1.34 Å) C–N bond length. The C–S bond length is 1.72 Å. There are eight inequivalent N3- sites. In the first N3- site, N3- is bonded in a trigonal planar geometry to one C4+ and two H1+ atoms. There is one shorter (1.02 Å) and one longer (1.03 Å) N–H bond length. In the second N3- site, N3- is bonded in a trigonal planar geometry to one C4+ and two H1+ atoms. Both N–H bond lengths are 1.02 Å. In the third N3- site, N3- is bonded in a trigonal planar geometry to one C4+ and two H1+ atoms. There is one shorter (1.02 Å) and one longer (1.03 Å) N–H bond length. In the fourth N3- site, N3- is bonded in a trigonal planar geometry to one C4+ and two H1+ atoms. Both N–H bond lengths are 1.02 Å. In the fifth N3- site, N3- is bonded in a trigonal planar geometry to one C4+ and two H1+ atoms. There is one shorter (1.02 Å) and one longer (1.03 Å) N–H bond length. In the sixth N3- site, N3- is bonded in a trigonal planar geometry to one C4+ and two H1+ atoms. Both N–H bond lengths are 1.02 Å. In the seventh N3- site, N3- is bonded in a trigonal planar geometry to one C4+ and two H1+ atoms. There is one shorter (1.02 Å) and one longer (1.03 Å) N–H bond length. In the eighth N3- site, N3- is bonded in a trigonal planar geometry to one C4+ and two equivalent H1+ atoms. Both N–H bond lengths are 1.02 Å. There are fifteen inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the seventh H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the eighth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the ninth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the tenth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the eleventh H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the twelfth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the thirteenth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the fourteenth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the fifteenth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded in a water-like geometry to one Pd2+ and one C4+ atom. In the second S2- site, S2- is bonded in a water-like geometry to one Pd2+ and one C4+ atom. In the third S2- site, S2- is bonded in a water-like geometry to one Pd2+ and one C4+ atom. In the fourth S2- site, S2- is bonded in a water-like geometry to one Pd2+ and one C4+ atom.

36 MATERIALS SCIENCE↗