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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Atomically Dispersed CuN x Sites from Thermal Activation of Boron Imidazolate Cages for Electrocatalytic Methane Generation

Atomically dispersed metal sites (ADMSs) have been recognized as promising candidates for electrochemical conversion. Among a diverse range of molecular precursors for ADMS synthesis, framework materials are particularly interesting due to their high degree of tunability and control over the primary coordination sphere of the metal ions. In this work, we demonstrate that a copper boron imidazolate cage, BIF-29(Cu), is a convenient precursor for a competent catalyst with isolated Cu sites coordinated by N donors for carbon dioxide electroreduction (CO 2 RR). Although BIF-29(Cu) exhibited moderate methane selectivity over hydrogen evolution reaction (HER), the methane selectivity is significantly enhanced by 2 times (55% CH 4 at –1.25 V vs RHE) after mild thermal activation. Extensive characterization methods indicate the transformation of crystalline BIF-29(Cu) into an amorphous carbonaceous material comprising isolated CuN x sites. Moreover, in situ X-ray absorbance spectroscopy indicates stable CuN x sites that are reduced during CO 2 RR. This work encourages the discovery of single-site electrocatalytic systems through a rational selection of molecular precursor and calcination parameters for promoting product selectivity.

10 SYNTHETIC FUELS↗
DOE OSTI2025

Manipulating the Second Coordination Shell of Single-Atom Fe for Enhanced Fenton Reaction

While current methods use oxidizable metals as electron donors to effectively reduce Fe 3+ , they suffer from the irreversible oxidation of these metals, ultimately compromising the catalyst’s longevity. To address this challenge, we engineered the second coordination shell of a single-atom Fe center by doping boron (B) onto a graphene-based support (Fe 1 /B-graphene) and utilized H 2 O 2 as the electron source for efficient Fe 2+ regeneration. Experimental results, supported by theoretical calculations, revealed that the Fe–O–B motif functions like a micro galvanic cell, with intermediary O atoms facilitating electron transfer between electrodes. Specifically, electrons consumed during H 2 O 2 activation at Fe 1 sites (positive electrode) are replenished by electrons extracted from H 2 O 2 at B atoms (negative electrode), where the activation energy for H 2 O 2 oxidation is significantly lower than that at Fe 1 sites. This study offers inspirational insights into the design of Fenton catalysts through precise regulation of the second coordination shell, demonstrating the potential of tailoring the outer coordination environment of single-atom catalysts to enhance catalytic performance across various reactions.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Beyond Ammonia: Nitrogen–Element Bond Forming Reactions with Coordinated Dinitrogen

The functionalization of coordinated dinitrogen to form nitrogen-element bonds en route to nitrogen-containing molecules is a long-standing challenge in chemical synthesis. The strong triple bond and the non-polarity of the N 2 molecule pose thermodynamic and kinetic challenges for promoting reactivity. Although heterogeneous, homogeneous and biological catalysts are all known for catalytic nitrogen fixation to ammonia, the catalytic synthesis of more complicated nitrogen-containing organic molecules has far less precedent. Examples of silyl radical additions to coordinated nitrogen to form silylamines stands as the lone example of a catalytic reaction involving N 2 to form a product other than ammonia. Our review surveys the field of molecular transition metal complexes, as well as recent boron examples for the formation of nitrogen-element bonds. Emphasis is placed on the coordination and activation modes of N 2 in the various metal compounds from across the transition series and how these structures can rationally inform reactivity studies. Over the past few decades, the field has evolved from the addition of carbon electrophiles in a manner similar to protonation reactions to more organometallic-inspired reactivity including insertions, 1,2-additions and cycloadditions. Various N–C, N–Si and N–B bond-forming reactions have been discovered highlighting that the challenge for catalytic chemistry is not in the reactivity of coordinated dinitrogen but rather removal of the functionalized ligand from the coordination sphere of the metal.

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

Facile Oxide to Chalcogenide Conversion for Actinides Using the Boron–Chalcogen Mixture Method

Actinide chalcogenides are of interest for fundamental studies of the behavior of 5f electrons in actinides located in a soft ligand coordination environment. As actinides exhibit an extremely high affinity for oxygen, the synthesis of phase pure actinide chalcogenide materials free of oxide impurities is a great challenge and, moreover, requires the availability and use of oxygen free starting materials. Herein, we report a new method, the Boron-Chalcogen Mixture (BCM) method, for the synthesis of phase pure uranium chalcogenides based on the use of a boron/chalcogen mixture, where boron functions as an “oxygen sponge” to remove oxygen from an oxide precursor and where the elemental chalcogen effects transformation of the oxide precursor into an oxygen free chalcogenide reagent. Here, the boron oxide can be separated from the reaction mixture that is left to react to form the desired chalcogenide product. Several syntheses are presented that demonstrate the broad functionali-ty of the technique and thermodynamic calculations that show the underlying driving force are discussed. Specifically, three classes of chalcogenides that include both new (rare earth uranium sulfides and alkali-thorium thiophosphates) and previously reported compounds were prepared to validate the approach: binary uranium and thorium sulfides, oxide to sulfide transfor-mation in solid state reactions, and in situ generation of actinide chalcogenides in flux crystal growth reactions.

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

Materials Data on KBC4NF9 by Materials Project

KC4NF9B crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional and consists of four boron molecules and one KC4NF9 framework. In the KC4NF9 framework, K1+ is bonded in a 10-coordinate geometry to one N3- and nine F1- atoms. The K–N bond length is 2.75 Å. There are a spread of K–F bond distances ranging from 2.76–3.06 Å. There are three inequivalent C2+ sites. In the first C2+ site, C2+ is bonded in a single-bond geometry to one N3- atom. The C–N bond length is 1.16 Å. In the second C2+ site, C2+ is bonded in a trigonal non-coplanar geometry to three F1- atoms. All C–F bond lengths are 1.38 Å. In the third C2+ site, C2+ is bonded in a trigonal non-coplanar geometry to three F1- atoms. There is two shorter (1.38 Å) and one longer (1.39 Å) C–F bond length. N3- is bonded in a linear geometry to one K1+ and one C2+ atom. There are five inequivalent F1- sites. In the first F1- site, F1- is bonded in a distorted single-bond geometry to one K1+ and one C2+ atom. In the second F1- site, F1- is bonded in a single-bond geometry to one K1+ and one C2+ atom. In the third F1- site, F1- is bonded in a single-bond geometry to one K1+ and one C2+ atom. In the fourth F1- site, F1- is bonded in a single-bond geometry to one K1+ and one C2+ atom. In the fifth F1- site, F1- is bonded in a single-bond geometry to one K1+ and one C2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sn3B by Materials Project

B(Sn)3 is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional and consists of one boron molecule and one Sn framework. In the Sn framework, Sn is bonded in a 8-coordinate geometry to eight equivalent Sn atoms. All Sn–Sn bond lengths are 3.20 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CsB(CN)4 by Materials Project

Cs(CN)4B crystallizes in the tetragonal I4_1/a space group. The structure is three-dimensional and consists of four boron molecules and one Cs(CN)4 framework. In the Cs(CN)4 framework, Cs1+ is bonded in a 8-coordinate geometry to eight equivalent N3- atoms. There are four shorter (3.30 Å) and four longer (3.44 Å) Cs–N bond lengths. C2+ is bonded in a single-bond geometry to one N3- atom. The C–N bond length is 1.17 Å. N3- is bonded in a distorted single-bond geometry to two equivalent Cs1+ and one C2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on RbB(CN)4 by Materials Project

Rb(CN)4B crystallizes in the tetragonal I4_1/a space group. The structure is three-dimensional and consists of four boron molecules and one Rb(CN)4 framework. In the Rb(CN)4 framework, Rb1+ is bonded in a 8-coordinate geometry to eight equivalent N3- atoms. There are four shorter (3.11 Å) and four longer (3.33 Å) Rb–N bond lengths. C2+ is bonded in a single-bond geometry to one N3- atom. The C–N bond length is 1.17 Å. N3- is bonded in a distorted single-bond geometry to two equivalent Rb1+ and one C2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TlB(CN)4 by Materials Project

BTl(CN)4 crystallizes in the tetragonal I4_1/a space group. The structure is three-dimensional and consists of four boron molecules and one Tl(CN)4 framework. In the Tl(CN)4 framework, Tl1+ is bonded in a 8-coordinate geometry to eight equivalent N3- atoms. There are four shorter (3.03 Å) and four longer (3.32 Å) Tl–N bond lengths. C2+ is bonded in a single-bond geometry to one N3- atom. The C–N bond length is 1.17 Å. N3- is bonded in a distorted single-bond geometry to two equivalent Tl1+ and one C2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KB(CF3)4 by Materials Project

K(CF3)4B crystallizes in the orthorhombic P2_12_12_1 space group. The structure is three-dimensional and consists of four boron molecules and one K(CF3)4 framework. In the K(CF3)4 framework, K1+ is bonded in a 10-coordinate geometry to ten F1- atoms. There are a spread of K–F bond distances ranging from 2.65–3.22 Å. There are four inequivalent C2+ sites. In the first C2+ site, C2+ is bonded in a trigonal non-coplanar geometry to three F1- atoms. All C–F bond lengths are 1.38 Å. In the second C2+ site, C2+ is bonded in a trigonal non-coplanar geometry to three F1- atoms. There are a spread of C–F bond distances ranging from 1.37–1.39 Å. In the third C2+ site, C2+ is bonded in a trigonal non-coplanar geometry to three F1- atoms. There is one shorter (1.37 Å) and two longer (1.39 Å) C–F bond length. In the fourth C2+ site, C2+ is bonded in a trigonal non-coplanar geometry to three F1- atoms. All C–F bond lengths are 1.38 Å. There are twelve inequivalent F1- sites. In the first F1- site, F1- is bonded in a distorted single-bond geometry to one K1+ and one C2+ atom. In the second F1- site, F1- is bonded in a distorted single-bond geometry to one K1+ and one C2+ atom. In the third F1- site, F1- is bonded in a single-bond geometry to one K1+ and one C2+ atom. In the fourth F1- site, F1- is bonded in a single-bond geometry to one K1+ and one C2+ atom. In the fifth F1- site, F1- is bonded in a single-bond geometry to one K1+ and one C2+ atom. In the sixth F1- site, F1- is bonded in a single-bond geometry to one C2+ atom. In the seventh F1- site, F1- is bonded in a distorted single-bond geometry to one K1+ and one C2+ atom. In the eighth F1- site, F1- is bonded in a single-bond geometry to one K1+ and one C2+ atom. In the ninth F1- site, F1- is bonded in a single-bond geometry to one K1+ and one C2+ atom. In the tenth F1- site, F1- is bonded in a single-bond geometry to one K1+ and one C2+ atom. In the eleventh F1- site, F1- is bonded in a single-bond geometry to one C2+ atom. In the twelfth F1- site, F1- is bonded in a single-bond geometry to one K1+ and one C2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg(B6C)2 by Materials Project

B12C2Mg crystallizes in the orthorhombic Imma space group. The structure is zero-dimensional and consists of twenty-four boron, metallic molecules and four Mg(B3C)2 clusters. In each Mg(B3C)2 cluster, Mg2+ is bonded in a 2-coordinate geometry to two equivalent C4- atoms. Both Mg–C bond lengths are 2.29 Å. There are two inequivalent B+0.50+ sites. In the first B+0.50+ site, B+0.50+ is bonded in a single-bond geometry to one C4- atom. The B–C bond length is 1.66 Å. In the second B+0.50+ site, B+0.50+ is bonded in a single-bond geometry to one C4- atom. The B–C bond length is 1.65 Å. C4- is bonded in a 5-coordinate geometry to one Mg2+, three B+0.50+, and one C4- atom. The C–C bond length is 1.72 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Regulating the Catalytic Activity of Pd Nanoparticles by Confinement in Ordered Mesoporous Supports

Studying structure-sensitive reactions requires the synthesis of catalytic nanoparticles with precisely controlled sizes. Here we demonstrate the facile production of size controlled Pd nanoparticles by confinement in the pores of mesoporous silica nanoparticles (MSN). We show that Pd particles 2.1 nm in size have a higher catalytic activity than larger nanoparticles for the Suzuki-Miyaura cross coupling between 4’-bromoacteophenone and phenyl boronic acid and for the hydrogenation of phenol in aqueous phase. The enhanced activity can be explained in terms of increased number of coordinatively unsaturated sites and higher back donation capacity of the small nanoparticles.

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

Materials Data on K2O2 by Materials Project

K2O2 is alpha boron-derived structured and crystallizes in the orthorhombic Cmce space group. The structure is three-dimensional. K is bonded in a 6-coordinate geometry to six equivalent O atoms. There are two shorter (2.71 Å) and four longer (2.75 Å) K–O bond lengths. O is bonded in a 7-coordinate geometry to six equivalent K and one O atom. The O–O bond length is 1.53 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CsS by Materials Project

SCs is alpha boron-derived structured and crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. Cs1+ is bonded in a 6-coordinate geometry to six equivalent S1- atoms. There are four shorter (3.52 Å) and two longer (3.61 Å) Cs–S bond lengths. S1- is bonded in a 7-coordinate geometry to six equivalent Cs1+ and one S1- atom. The S–S bond length is 2.12 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on RbS by Materials Project

RbS is alpha boron-derived structured and crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. Rb1+ is bonded in a 6-coordinate geometry to six equivalent S1- atoms. There are four shorter (3.38 Å) and two longer (3.41 Å) Rb–S bond lengths. S1- is bonded in a 7-coordinate geometry to six equivalent Rb1+ and one S1- atom. The S–S bond length is 2.13 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Rb2O2 by Materials Project

Rb2O2 is alpha boron-derived structured and crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. Rb is bonded in a 6-coordinate geometry to six equivalent O atoms. There are four shorter (2.85 Å) and two longer (2.94 Å) Rb–O bond lengths. O is bonded in a 7-coordinate geometry to six equivalent Rb and one O atom. The O–O bond length is 1.53 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cs2O2 by Materials Project

Cs2O2 is alpha boron-derived structured and crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. Cs is bonded in a 6-coordinate geometry to six equivalent O atoms. There are four shorter (2.98 Å) and two longer (3.20 Å) Cs–O bond lengths. O is bonded in a 7-coordinate geometry to six equivalent Cs and one O atom. The O–O bond length is 1.52 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KB6H4(OF3)2 by Materials Project

KB4H4(OF2)2(FB1)2 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of eight boron monofluoride molecules and two KB4H4(OF2)2 clusters. In one of the KB4H4(OF2)2 clusters, K is bonded in a 7-coordinate geometry to three O and four F atoms. There are a spread of K–O bond distances ranging from 2.71–2.92 Å. There are a spread of K–F bond distances ranging from 2.69–3.02 Å. There are four inequivalent B sites. In the first B site, B is bonded in a single-bond geometry to one F atom. The B–F bond length is 1.40 Å. In the second B site, B is bonded in a single-bond geometry to one F atom. The B–F bond length is 1.40 Å. In the third B site, B is bonded in a single-bond geometry to one F atom. The B–F bond length is 1.39 Å. In the fourth B site, B is bonded in a single-bond geometry to one F atom. The B–F bond length is 1.39 Å. There are four inequivalent H sites. In the first H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.99 Å. In the second H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.98 Å. In the third H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.98 Å. In the fourth H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.97 Å. There are two inequivalent O sites. In the first O site, O is bonded in a water-like geometry to one K and two H atoms. In the second O site, O is bonded in a water-like geometry to two equivalent K and two H atoms. There are four inequivalent F sites. In the first F site, F is bonded in a single-bond geometry to one K and one B atom. In the second F site, F is bonded in a distorted single-bond geometry to one K and one B atom. In the third F site, F is bonded in a distorted single-bond geometry to one K and one B atom. In the fourth F site, F is bonded in a single-bond geometry to one K and one B atom. In one of the KB4H4(OF2)2 clusters, K is bonded in a 7-coordinate geometry to three O and four F atoms. There are a spread of K–O bond distances ranging from 2.77–2.86 Å. There are a spread of K–F bond distances ranging from 2.82–3.19 Å. There are four inequivalent B sites. In the first B site, B is bonded in a single-bond geometry to one F atom. The B–F bond length is 1.40 Å. In the second B site, B is bonded in a single-bond geometry to one F atom. The B–F bond length is 1.40 Å. In the third B site, B is bonded in a single-bond geometry to one F atom. The B–F bond length is 1.41 Å. In the fourth B site, B is bonded in a single-bond geometry to one F atom. The B–F bond length is 1.40 Å. There are four inequivalent H sites. In the first H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.99 Å. In the second H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.98 Å. In the third H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.98 Å. In the fourth H site, H is bonded in a single-bond geometry to one O atom. The H–O bond length is 0.98 Å. There are two inequivalent O sites. In the first O site, O is bonded in a distorted water-like geometry to two equivalent K and two H atoms. In the second O site, O is bonded in a water-like geometry to one K and two H atoms. There are four inequivalent F sites. In the first F site, F is bonded in a distorted single-bond geometry to one K and one B atom. In the second F site, F is bonded in a single-bond geometry to one K and one B atom. In the third F site, F is bonded in a single-bond geometry to one K and one B atom. In the fourth F site, F is bonded in a distorted single-bond geometry to one K and one B atom.

36 MATERIALS SCIENCE↗