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All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Demonstration of no catalytical activity of Fe–N–C and Nb–N–C electrocatalysts toward nitrogen reduction using in–line quantification

Ammonia (NH 3 ) production via the electrochemical nitrogen reduction reaction (NRR) is a promising method for sustainable generation of this important chemical. Efforts are ongoing in finding an efficient, stable, and selective catalyst that will enable the reaction. However, progress is hindered in the field due to lack of reproducibility, most likely a consequence of reports of false-positive results due to improper measurement control and methods. In this study, we explore the NRR activity of a promising class of single atom catalysts, transition metal-nitrogen-carbon (M-N-C) electrocatalysts. Using a state-of-the-art in-line ammonia quantification methodology, with detection limit as low as 1 ppb for ammonia, we show that single atom Nb and Fe embedded in a stable carbon and nitrogen framework do not electrochemically reduce N 2 to NH 3 . Critically, this demonstrates that our experimental setup with in-line sequential injection analysis successfully excludes ammonia contamination from the gas supply and atmospheric sources, allowing for thorough and high-throughput examination of potential NRR catalysts.

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

Facile and Scalable Synthesis of Metal- and Nitrogen-Doped Carbon Nanotubes for Efficient Electrochemical CO 2 Reduction

Metal- and nitrogen-doped carbon (M–N–C) is a promising material to catalyze electrochemical CO 2 reduction reaction (CO 2 RR). However, most M–N–C catalysts in the literature require complicated synthesis procedures and produce small quantities per batch, limiting the commercialization potential. In this work, we developed a simple and scalable synthesis method to convert metal-impurity-containing commercial carbon nanotubes (CNTs) and nitrogen-containing organic precursors into M–N–C via one-step moderate-temperature (650 °C) pyrolysis without any other treatment nor the need to add metal precursors. Batches of catalysts in varied mass up to 10 g (150 mL in volume) per batch were synthesized, and repeatable catalytic performances were demonstrated. To the best of our knowledge, the 10 g batch is one of the largest batches of CO2RR catalysts synthesized in the literature while requiring minimal synthesis steps. The catalyst possessed single-atomic iron–nitrogen (Fe–N) sites, enabling a high performance of >95% CO product selectivity at a high current density of 400 mA/cm 2 and high stability for 45 h at 100 mA/cm 2 in a flow cell testing. The catalyst outperformed a benchmark noble-metal nanoparticle catalyst and achieved longer stability than many other reported M–N–C catalysts in the literature. The scalable and cost-effective synthesis developed in this work paves a pathway toward practical CO 2 RR applications. The direct utilization of metal impurities from raw CNTs for efficient catalyst synthesis with minimal treatment is a green and sustainable engineering approach.

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

Materials Data on Zr2Fe2F3 by Materials Project

Zr2Fe2F3 crystallizes in the monoclinic Cm space group. The structure is two-dimensional and consists of one Zr2Fe2F3 sheet oriented in the (0, 0, 1) direction. there are three inequivalent Zr sites. In the first Zr site, Zr is bonded in a 4-coordinate geometry to one Fe and four F atoms. The Zr–Fe bond length is 2.84 Å. There are a spread of Zr–F bond distances ranging from 2.18–2.44 Å. In the second Zr site, Zr is bonded in a 3-coordinate geometry to one Fe and three F atoms. The Zr–Fe bond length is 2.68 Å. There are a spread of Zr–F bond distances ranging from 2.09–2.35 Å. In the third Zr site, Zr is bonded in a 3-coordinate geometry to three F atoms. There are one shorter (2.21 Å) and two longer (2.38 Å) Zr–F bond lengths. There are three inequivalent Fe sites. In the first Fe site, Fe is bonded in a single-bond geometry to one F atom. The Fe–F bond length is 1.97 Å. In the second Fe site, Fe is bonded in a distorted single-bond geometry to one F atom. The Fe–F bond length is 2.35 Å. In the third Fe site, Fe is bonded in a 3-coordinate geometry to three Zr atoms. There are four inequivalent F sites. In the first F site, F is bonded in a 3-coordinate geometry to three Zr atoms. In the second F site, F is bonded in a bent 150 degrees geometry to one Zr and one Fe atom. In the third F site, F is bonded in a trigonal non-coplanar geometry to three Zr atoms. In the fourth F site, F is bonded in a 3-coordinate geometry to two Zr and one Fe atom.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Large Anomalous and Topological Hall Effect and Nernst Effect in a Dirac Kagome Magnet Fe 3 Ge

Searching for Kagome magnets with novel magnetic and electronic properties has been attracting significant efforts recently. Here, the magnetic, electronic, and thermoelectric properties of Fe 3 Ge single crystals with Fe atoms forming a slightly distorted Kagome lattice are reported. It is shown that Fe 3 Ge exhibits a large anomalous Hall effect and anomalous Nernst effect. The observed anomalous transverse thermoelectric conductivity $|α^A_{xz}|$ reaches ≈4.6 A m −1 K −1 , which is larger than the conventional ferromagnets and most of the topological ferromagnets reported in literature. The first-principles calculations suggest that these exceptional transport properties are dominated by the intrinsic mechanism, which highlights the significant contribution of the Berry curvature of massive Dirac gaps in the momentum space. Additionally, a topological Hall resistivity of 0.9 µΩ cm and a topological Nernst coefficient of 1.2 µV K −1 are also observed, which are presumably ascribed to the Berry phase associated with the field-induced non-zero scalar spin chirality. These features highlight the synergic effects of the Berry phases in both momentum space and real space of Fe 3 Ge, which render it an excellent candidate for room-temperature thermoelectric applications based on transverse transport.

Kagome magnet↗
DOE OSTI2020

Manipulating the Geometric and Electronic Structures of Manganese Nitrides for Ammonia Synthesis

Abstract Manganese (Mn) nitrides are important nitrogen (N) carriers for small‐scale intermittent ammonia (NH 3 ) synthesis. However, only 3∼8 % of lattice N are converted into NH 3 . In this study, the geometric and electronic structures of well‐defined Mn 4 N and Mn 2 N lattices were altered using transition metal heteroatoms (Cr, Fe, Co, Ni, Mo) to understand the driving force behind lattice N diffusion and extraction. Density Functional Theory (DFT) revealed that the binding of early hydrogenation product (NH) follows a linear relationship with lattice N over a wide range of close‐packed surfaces. But, the binding of NH 2 and NH 3 are more sensitive to the geometric and electronic structures. Further, the chemical bonding can be quantitatively characterized with the covalency derived from Crystal Orbital Hamiltonian Population (COHP). In the Eley Rideal‐Mars van Krevelan pathway, the overall NH 3 formation free energy ( ) and lattice N diffusion barrier ( ) are the respective thermodynamic and kinetic determining factors. Aided by a rate‐determining step (RDS) model, Mn 4 N modified with Fe, Co, Ni single‐atom dopants all show enhanced rates for NH 3 formation.

Shan, Nannan↗
DOE OSTI2020

Materials Data on K2FeCl5O by Materials Project

K2FeOCl5 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. K is bonded in a 10-coordinate geometry to ten Cl atoms. There are a spread of K–Cl bond distances ranging from 3.29–3.62 Å. Fe is bonded in a distorted octahedral geometry to one O and five Cl atoms. The Fe–O bond length is 1.78 Å. There are a spread of Fe–Cl bond distances ranging from 2.30–2.44 Å. O is bonded in a single-bond geometry to one Fe atom. There are four inequivalent Cl sites. In the first Cl site, Cl is bonded to four equivalent K and one Fe atom to form a mixture of face, edge, and corner-sharing ClK4Fe square pyramids. In the second Cl site, Cl is bonded to four equivalent K and one Fe atom to form a mixture of distorted face, edge, and corner-sharing ClK4Fe square pyramids. In the third Cl site, Cl is bonded to four equivalent K and one Fe atom to form a mixture of distorted face, edge, and corner-sharing ClK4Fe square pyramids. In the fourth Cl site, Cl is bonded in a distorted single-bond geometry to four equivalent K and one Fe atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Fe(ClO2)3 by Materials Project

(Fe(O3Cl)2)2Cl2 crystallizes in the monoclinic C2/m space group. The structure is one-dimensional and consists of two hydrochloric acid molecules and two Fe(O3Cl)2 ribbons oriented in the (0, 1, 0) direction. In each Fe(O3Cl)2 ribbon, Fe is bonded in an octahedral geometry to four equivalent O and two equivalent Cl atoms. All Fe–O bond lengths are 2.19 Å. Both Fe–Cl bond lengths are 2.28 Å. There are two inequivalent O sites. In the first O site, O is bonded in a water-like geometry to one Fe and one O atom. The O–O bond length is 1.35 Å. In the second O site, O is bonded in a bent 120 degrees geometry to two equivalent O atoms. Cl is bonded in a single-bond geometry to one Fe atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho2Ga4Fe13C2 by Materials Project

Ho2Fe13Ga4C2 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are two inequivalent Ho sites. In the first Ho site, Ho is bonded in a distorted bent 120 degrees geometry to seven Fe, two equivalent Ga, and two C atoms. There are a spread of Ho–Fe bond distances ranging from 3.12–3.36 Å. There are one shorter (3.12 Å) and one longer (3.50 Å) Ho–Ga bond lengths. There are one shorter (2.46 Å) and one longer (2.49 Å) Ho–C bond lengths. In the second Ho site, Ho is bonded in a distorted bent 120 degrees geometry to eight Fe, one Ga, and two C atoms. There are a spread of Ho–Fe bond distances ranging from 3.09–3.51 Å. The Ho–Ga bond length is 3.17 Å. There are one shorter (2.48 Å) and one longer (2.53 Å) Ho–C bond lengths. There are thirteen inequivalent Fe sites. In the first Fe site, Fe is bonded in a single-bond geometry to five Fe, one Ga, and one C atom. There are a spread of Fe–Fe bond distances ranging from 2.49–2.78 Å. The Fe–Ga bond length is 2.61 Å. The Fe–C bond length is 1.84 Å. In the second Fe site, Fe is bonded in a single-bond geometry to six Fe and one C atom. There are a spread of Fe–Fe bond distances ranging from 2.46–2.78 Å. The Fe–C bond length is 1.86 Å. In the third Fe site, Fe is bonded to two Ho, eight Fe, and two Ga atoms to form distorted FeHo2Ga2Fe8 cuboctahedra that share a cornercorner with one GaHo3GaFe8 cuboctahedra, corners with seven FeHo2Ga3Fe7 cuboctahedra, corners with four CHo2GaFe3 octahedra, edges with three FeHo2Ga3Fe7 cuboctahedra, edges with two CHo2GaFe3 octahedra, faces with two equivalent GaHo3GaFe8 cuboctahedra, and faces with seven FeHo2Ga3Fe7 cuboctahedra. The corner-sharing octahedra tilt angles range from 23–31°. There are a spread of Fe–Fe bond distances ranging from 2.44–2.73 Å. There are one shorter (2.53 Å) and one longer (2.61 Å) Fe–Ga bond lengths. In the fourth Fe site, Fe is bonded in a single-bond geometry to five Fe, one Ga, and one C atom. There are a spread of Fe–Fe bond distances ranging from 2.46–2.77 Å. The Fe–Ga bond length is 2.70 Å. The Fe–C bond length is 1.85 Å. In the fifth Fe site, Fe is bonded to two Ho, seven Fe, and three Ga atoms to form distorted FeHo2Ga3Fe7 cuboctahedra that share a cornercorner with one GaHo3GaFe8 cuboctahedra, corners with seven FeHo2Ga2Fe8 cuboctahedra, corners with four CHo2GaFe3 octahedra, edges with three FeHo2Ga2Fe8 cuboctahedra, edges with two CHo2GaFe3 octahedra, faces with two equivalent GaHo3GaFe8 cuboctahedra, and faces with seven FeHo2Ga2Fe8 cuboctahedra. The corner-sharing octahedra tilt angles range from 23–29°. There are a spread of Fe–Fe bond distances ranging from 2.46–2.75 Å. There are two shorter (2.52 Å) and one longer (2.67 Å) Fe–Ga bond lengths. In the sixth Fe site, Fe is bonded in a single-bond geometry to six Fe and one C atom. There are a spread of Fe–Fe bond distances ranging from 2.47–2.79 Å. The Fe–C bond length is 1.83 Å. In the seventh Fe site, Fe is bonded in a 1-coordinate geometry to one Ho, ten Fe, and three Ga atoms. There are a spread of Fe–Fe bond distances ranging from 2.37–2.72 Å. There are a spread of Fe–Ga bond distances ranging from 2.64–2.68 Å. In the eighth Fe site, Fe is bonded in a 3-coordinate geometry to one Ho, twelve Fe, and one Ga atom. There are a spread of Fe–Fe bond distances ranging from 2.57–2.70 Å. The Fe–Ga bond length is 2.57 Å. In the ninth Fe site, Fe is bonded to two Ho, seven Fe, and three Ga atoms to form distorted FeHo2Ga3Fe7 cuboctahedra that share a cornercorner with one GaHo3GaFe8 cuboctahedra, corners with seven FeHo2Ga2Fe8 cuboctahedra, corners with two equivalent CHo2GaFe3 octahedra, an edgeedge with one GaHo3GaFe8 cuboctahedra, edges with three FeHo2Ga2Fe8 cuboctahedra, a faceface with one GaHo3GaFe8 cuboctahedra, faces with seven FeHo2Ga2Fe8 cuboctahedra, and faces with two equivalent CHo2Ga2Fe2 octahedra. The corner-sharing octahedra tilt angles range from 40–44°. The Fe–Fe bond length is 2.41 Å. There are one shorter (2.47 Å) and two longer (2.50 Å) Fe–Ga bond lengths. In the tenth Fe site, Fe is bonded to two Ho, eight Fe, and two Ga atoms to form distorted FeHo2Ga2Fe8 cuboctahedra that share a cornercorner with one GaHo3GaFe8 cuboctahedra, corners with seven FeHo2Ga2Fe8 cuboctahedra, corners with two equivalent CHo2Ga2Fe2 octahedra, an edgeedge with one GaHo3GaFe8 cuboctahedra, edges with three FeHo2Ga2Fe8 cuboctahedra, a faceface with one GaHo3GaFe8 cuboctahedra, faces with seven FeHo2Ga2Fe8 cuboctahedra, and faces with two equivalent CHo2GaFe3 octahedra. The corner-sharing octahedra tilt angles range from 42–43°. Both Fe–Fe bond lengths are 2.42 Å. There are one shorter (2.45 Å) and one longer (2.47 Å) Fe–Ga bond lengths. In the eleventh Fe site, Fe is bonded to two Ho, seven Fe, and three Ga atoms to form distorted FeHo2Ga3Fe7 cuboctahedra that share corners with three equivalent GaHo3GaFe8 cuboctahedra, corners with eleven FeHo2Ga2Fe8 cuboctahedra, an edgeedge with one FeHo3Ga2Fe7 cuboctahedra, an edgeedge with one GaHo3GaFe8 cuboctahedra, a faceface with one GaHo3GaFe8 cuboctahedra, faces with nine FeHo2Ga2Fe8 cuboctahedra, and faces with four CHo2GaFe3 octahedra. The Fe–Fe bond length is 2.42 Å. There are a spread of Fe–Ga bond distances ranging from 2.47–2.52 Å. In the twelfth Fe site, Fe is bonded to three Ho, seven Fe, and two Ga atoms to form distorted FeHo3Ga2Fe7 cuboctahedra that share corners with two equivalent GaHo3GaFe8 cuboctahedra, corners with nine FeHo2Ga2Fe8 cuboctahedra, corners with four CHo2GaFe3 octahedra, an edgeedge with one GaHo3GaFe8 cuboctahedra, edges with three FeHo2Ga3Fe7 cuboctahedra, a faceface with one GaHo3GaFe8 cuboctahedra, faces with seven FeHo2Ga2Fe8 cuboctahedra, and faces with two CHo2GaFe3 octahedra. The corner-sharing octahedra tilt angles range from 65–69°. There are one shorter (2.54 Å) and one longer (2.56 Å) Fe–Ga bond lengths. In the thirteenth Fe site, Fe is bonded in a single-bond geometry to four Fe, one Ga, and one C atom. The Fe–Ga bond length is 2.54 Å. The Fe–C bond length is 1.86 Å. There are four inequivalent Ga sites. In the first Ga site, Ga is bonded in a single-bond geometry to four Fe, one Ga, and one C atom. The Ga–Ga bond length is 2.64 Å. The Ga–C bond length is 2.08 Å. In the second Ga site, Ga is bonded to three Ho, eight Fe, and one Ga atom to form distorted GaHo3GaFe8 cuboctahedra that share corners with two equivalent GaHo3GaFe8 cuboctahedra, corners with nine FeHo2Ga2Fe8 cuboctahedra, corners with four CHo2GaFe3 octahedra, edges with four FeHo2Ga3Fe7 cuboctahedra, faces with eight FeHo2Ga2Fe8 cuboctahedra, and faces with two CHo2GaFe3 octahedra. The corner-sharing octahedra tilt angles range from 63–67°. In the third Ga site, Ga is bonded in a single-bond geometry to five Fe and one C atom. The Ga–C bond length is 2.16 Å. In the fourth Ga site, Ga is bonded in a single-bond geometry to five Fe and one C atom. The Ga–C bond length is 2.11 Å. There are two inequivalent C sites. In the first C site, C is bonded to two Ho, three Fe, and one Ga atom to form CHo2GaFe3 octahedra that share corners with two equivalent GaHo3GaFe8 cuboctahedra, corners with eight FeHo2Ga2Fe8 cuboctahedra, corners with two equivalent CHo2Ga2Fe2 octahedra, edges with two FeHo2Ga2Fe8 cuboctahedra, a faceface with one GaHo3GaFe8 cuboctahedra, and faces with five FeHo2Ga3Fe7 cuboctahedra. The corner-sharing octahedral tilt angles are 61°. In the second C site, C is bonded to two Ho, two Fe, and two Ga atoms to form CHo2Ga2Fe2 octahedra that share corners with two equivalent GaHo3GaFe8 cuboctahedra, corners with eight FeHo2Ga2Fe8 cuboctahedra, corners with two equivalent CHo2GaFe3 octahedra, edges with two FeHo2Ga2Fe8 cuboctahedra, a faceface with one GaHo3GaFe8 cuboctahedra, and faces with five FeHo2Ga3Fe7 cuboctahedra. The corner-sharing octahedral tilt angles are 61°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Er4Fe34C3 by Materials Project

Er4Fe34C3 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are two inequivalent Er sites. In the first Er site, Er is bonded in a distorted bent 120 degrees geometry to nine Fe and two C atoms. There are a spread of Er–Fe bond distances ranging from 3.03–3.36 Å. There are one shorter (2.49 Å) and one longer (2.50 Å) Er–C bond lengths. In the second Er site, Er is bonded in a distorted single-bond geometry to fourteen Fe and one C atom. There are a spread of Er–Fe bond distances ranging from 3.00–3.31 Å. The Er–C bond length is 2.52 Å. There are eighteen inequivalent Fe sites. In the first Fe site, Fe is bonded in a 2-coordinate geometry to one Er and thirteen Fe atoms. There are a spread of Fe–Fe bond distances ranging from 2.40–2.78 Å. In the second Fe site, Fe is bonded in a 2-coordinate geometry to one Er and thirteen Fe atoms. There are a spread of Fe–Fe bond distances ranging from 2.61–2.77 Å. In the third Fe site, Fe is bonded in a single-bond geometry to five Fe and one C atom. There are a spread of Fe–Fe bond distances ranging from 2.46–2.56 Å. The Fe–C bond length is 1.92 Å. In the fourth Fe site, Fe is bonded in a single-bond geometry to seven Fe and one C atom. There are a spread of Fe–Fe bond distances ranging from 2.47–2.57 Å. The Fe–C bond length is 1.92 Å. In the fifth Fe site, Fe is bonded in a single-bond geometry to five Fe and one C atom. There are a spread of Fe–Fe bond distances ranging from 2.47–2.57 Å. The Fe–C bond length is 1.92 Å. In the sixth Fe site, Fe is bonded to three equivalent Er and nine Fe atoms to form FeEr3Fe9 cuboctahedra that share corners with thirteen FeEr2Fe10 cuboctahedra, corners with two equivalent CEr2Fe4 octahedra, edges with seven FeEr2Fe10 cuboctahedra, faces with ten FeEr2Fe10 cuboctahedra, and a faceface with one CEr2Fe4 octahedra. The corner-sharing octahedra tilt angles range from 66–70°. There are a spread of Fe–Fe bond distances ranging from 2.47–2.63 Å. In the seventh Fe site, Fe is bonded to three equivalent Er and nine Fe atoms to form FeEr3Fe9 cuboctahedra that share corners with ten FeEr2Fe10 cuboctahedra, corners with four CEr2Fe4 octahedra, edges with four FeEr2Fe10 cuboctahedra, faces with five FeEr2Fe10 cuboctahedra, and faces with two CEr2Fe4 octahedra. The corner-sharing octahedra tilt angles range from 63–69°. There are a spread of Fe–Fe bond distances ranging from 2.46–2.60 Å. In the eighth Fe site, Fe is bonded to three equivalent Er and nine Fe atoms to form FeEr3Fe9 cuboctahedra that share corners with thirteen FeEr2Fe10 cuboctahedra, corners with two equivalent CEr2Fe4 octahedra, edges with six FeEr2Fe10 cuboctahedra, faces with ten FeEr2Fe10 cuboctahedra, and a faceface with one CEr2Fe4 octahedra. The corner-sharing octahedra tilt angles range from 65–69°. There are a spread of Fe–Fe bond distances ranging from 2.46–2.61 Å. In the ninth Fe site, Fe is bonded in a single-bond geometry to seven Fe and one C atom. There are a spread of Fe–Fe bond distances ranging from 2.43–2.48 Å. The Fe–C bond length is 1.86 Å. In the tenth Fe site, Fe is bonded in a single-bond geometry to seven Fe and one C atom. There are a spread of Fe–Fe bond distances ranging from 2.41–2.48 Å. The Fe–C bond length is 1.85 Å. In the eleventh Fe site, Fe is bonded in a single-bond geometry to six Fe and one C atom. There are a spread of Fe–Fe bond distances ranging from 2.43–2.46 Å. The Fe–C bond length is 1.86 Å. In the twelfth Fe site, Fe is bonded in a 12-coordinate geometry to two equivalent Er and ten Fe atoms. There are a spread of Fe–Fe bond distances ranging from 2.43–2.51 Å. In the thirteenth Fe site, Fe is bonded in a 12-coordinate geometry to two equivalent Er and ten Fe atoms. Both Fe–Fe bond lengths are 2.44 Å. In the fourteenth Fe site, Fe is bonded to two equivalent Er and ten Fe atoms to form distorted FeEr2Fe10 cuboctahedra that share corners with nine FeEr2Fe10 cuboctahedra, corners with two equivalent CEr2Fe4 octahedra, edges with three FeEr2Fe10 cuboctahedra, an edgeedge with one CEr2Fe4 octahedra, and faces with twelve FeEr2Fe10 cuboctahedra. The corner-sharing octahedra tilt angles range from 25–30°. There are one shorter (2.43 Å) and one longer (2.44 Å) Fe–Fe bond lengths. In the fifteenth Fe site, Fe is bonded to two equivalent Er and ten Fe atoms to form FeEr2Fe10 cuboctahedra that share corners with eight FeEr2Fe10 cuboctahedra, corners with two equivalent CEr2Fe4 octahedra, edges with two equivalent FeEr3Fe9 cuboctahedra, faces with six FeEr2Fe10 cuboctahedra, and faces with two equivalent CEr2Fe4 octahedra. The corner-sharing octahedral tilt angles are 45°. In the sixteenth Fe site, Fe is bonded to two equivalent Er and ten Fe atoms to form FeEr2Fe10 cuboctahedra that share corners with eight FeEr2Fe10 cuboctahedra, corners with two equivalent CEr2Fe4 octahedra, edges with six FeEr3Fe9 cuboctahedra, and faces with ten FeEr2Fe10 cuboctahedra. The corner-sharing octahedral tilt angles are 44°. In the seventeenth Fe site, Fe is bonded to two Er and ten Fe atoms to form distorted FeEr2Fe10 cuboctahedra that share corners with ten FeEr2Fe10 cuboctahedra, a cornercorner with one CEr2Fe4 octahedra, edges with four FeEr3Fe9 cuboctahedra, faces with eight FeEr2Fe10 cuboctahedra, and faces with two equivalent CEr2Fe4 octahedra. The corner-sharing octahedral tilt angles are 44°. In the eighteenth Fe site, Fe is bonded to two Er and ten Fe atoms to form distorted FeEr2Fe10 cuboctahedra that share corners with thirteen FeEr2Fe10 cuboctahedra, edges with three FeEr3Fe9 cuboctahedra, faces with nine FeEr2Fe10 cuboctahedra, and faces with three CEr2Fe4 octahedra. There are two inequivalent C sites. In the first C site, C is bonded to two Er and four Fe atoms to form CEr2Fe4 octahedra that share corners with ten FeEr2Fe10 cuboctahedra, a cornercorner with one CEr2Fe4 octahedra, an edgeedge with one FeEr2Fe10 cuboctahedra, and faces with seven FeEr2Fe10 cuboctahedra. The corner-sharing octahedral tilt angles are 62°. In the second C site, C is bonded to two equivalent Er and four Fe atoms to form CEr2Fe4 octahedra that share corners with six FeEr2Fe10 cuboctahedra, corners with two equivalent CEr2Fe4 octahedra, and faces with six FeEr2Fe10 cuboctahedra. The corner-sharing octahedral tilt angles are 62°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sm2Ga2Fe15C2 by Materials Project

Sm2Fe15Ga2C2 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are two inequivalent Sm sites. In the first Sm site, Sm is bonded in a distorted bent 120 degrees geometry to nine Fe and two equivalent C atoms. There are a spread of Sm–Fe bond distances ranging from 3.10–3.44 Å. Both Sm–C bond lengths are 2.52 Å. In the second Sm site, Sm is bonded in a distorted bent 120 degrees geometry to nine Fe and two equivalent C atoms. There are a spread of Sm–Fe bond distances ranging from 3.06–3.49 Å. Both Sm–C bond lengths are 2.55 Å. There are ten inequivalent Fe sites. In the first Fe site, Fe is bonded in a 2-coordinate geometry to one Sm, eleven Fe, and two equivalent Ga atoms. There are a spread of Fe–Fe bond distances ranging from 2.40–2.79 Å. Both Fe–Ga bond lengths are 2.68 Å. In the second Fe site, Fe is bonded in a 2-coordinate geometry to one Sm and thirteen Fe atoms. There are a spread of Fe–Fe bond distances ranging from 2.57–2.77 Å. In the third Fe site, Fe is bonded in a single-bond geometry to six Fe and one C atom. There are a spread of Fe–Fe bond distances ranging from 2.45–2.61 Å. The Fe–C bond length is 1.85 Å. In the fourth Fe site, Fe is bonded in a single-bond geometry to six Fe and one C atom. There are a spread of Fe–Fe bond distances ranging from 2.48–2.55 Å. The Fe–C bond length is 1.84 Å. In the fifth Fe site, Fe is bonded to two Sm, nine Fe, and one Ga atom to form distorted FeSm2GaFe9 cuboctahedra that share corners with eight FeSm2GaFe9 cuboctahedra, corners with four equivalent CSm2GaFe3 octahedra, edges with three FeSm2GaFe9 cuboctahedra, edges with two equivalent CSm2GaFe3 octahedra, and faces with nine FeSm2GaFe9 cuboctahedra. The corner-sharing octahedra tilt angles range from 22–30°. There are a spread of Fe–Fe bond distances ranging from 2.45–2.71 Å. The Fe–Ga bond length is 2.56 Å. In the sixth Fe site, Fe is bonded to two Sm, nine Fe, and one Ga atom to form distorted FeSm2GaFe9 cuboctahedra that share corners with eight FeSm2GaFe9 cuboctahedra, corners with two equivalent CSm2GaFe3 octahedra, edges with four FeSm2GaFe9 cuboctahedra, faces with eight FeSm2GaFe9 cuboctahedra, and faces with two equivalent CSm2GaFe3 octahedra. The corner-sharing octahedra tilt angles range from 40–47°. There are a spread of Fe–Fe bond distances ranging from 2.43–2.46 Å. The Fe–Ga bond length is 2.50 Å. In the seventh Fe site, Fe is bonded to two Sm, eight Fe, and two equivalent Ga atoms to form distorted FeSm2Ga2Fe8 cuboctahedra that share corners with fourteen FeSm2GaFe9 cuboctahedra, edges with two FeSm3Ga2Fe7 cuboctahedra, faces with ten FeSm2GaFe9 cuboctahedra, and faces with four equivalent CSm2GaFe3 octahedra. Both Fe–Fe bond lengths are 2.47 Å. Both Fe–Ga bond lengths are 2.51 Å. In the eighth Fe site, Fe is bonded to three Sm, seven Fe, and two equivalent Ga atoms to form distorted FeSm3Ga2Fe7 cuboctahedra that share corners with eleven FeSm2GaFe9 cuboctahedra, corners with four equivalent CSm2GaFe3 octahedra, edges with four FeSm2GaFe9 cuboctahedra, faces with eight FeSm2GaFe9 cuboctahedra, and faces with two equivalent CSm2GaFe3 octahedra. The corner-sharing octahedra tilt angles range from 66–70°. Both Fe–Ga bond lengths are 2.59 Å. In the ninth Fe site, Fe is bonded in a single-bond geometry to five Fe and one C atom. The Fe–Fe bond length is 2.54 Å. The Fe–C bond length is 1.86 Å. In the tenth Fe site, Fe is bonded to three Sm and nine Fe atoms to form distorted FeSm3Fe9 cuboctahedra that share corners with eleven FeSm2GaFe9 cuboctahedra, corners with four equivalent CSm2GaFe3 octahedra, edges with four FeSm2GaFe9 cuboctahedra, faces with eight FeSm2GaFe9 cuboctahedra, and faces with two equivalent CSm2GaFe3 octahedra. The corner-sharing octahedra tilt angles range from 62–66°. Ga is bonded in a single-bond geometry to five Fe and one C atom. The Ga–C bond length is 2.16 Å. C is bonded to two Sm, three Fe, and one Ga atom to form CSm2GaFe3 octahedra that share corners with ten FeSm2GaFe9 cuboctahedra, corners with two equivalent CSm2GaFe3 octahedra, edges with two equivalent FeSm2GaFe9 cuboctahedra, and faces with six FeSm2GaFe9 cuboctahedra. The corner-sharing octahedra tilt angles range from 62–64°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sm4Cr3Fe31C4 by Materials Project

Sm4Cr3Fe31C4 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are four inequivalent Sm sites. In the first Sm site, Sm is bonded in a distorted bent 120 degrees geometry to eight Fe and two C atoms. There are a spread of Sm–Fe bond distances ranging from 3.05–3.39 Å. Both Sm–C bond lengths are 2.53 Å. In the second Sm site, Sm is bonded in a distorted bent 120 degrees geometry to one Cr, eight Fe, and two C atoms. The Sm–Cr bond length is 3.23 Å. There are a spread of Sm–Fe bond distances ranging from 3.04–3.40 Å. There are one shorter (2.53 Å) and one longer (2.54 Å) Sm–C bond lengths. In the third Sm site, Sm is bonded in a distorted bent 120 degrees geometry to one Cr, eight Fe, and two C atoms. The Sm–Cr bond length is 3.24 Å. There are a spread of Sm–Fe bond distances ranging from 3.04–3.40 Å. Both Sm–C bond lengths are 2.53 Å. In the fourth Sm site, Sm is bonded in a distorted bent 120 degrees geometry to one Cr, eight Fe, and two C atoms. The Sm–Cr bond length is 3.19 Å. There are a spread of Sm–Fe bond distances ranging from 3.01–3.43 Å. There are one shorter (2.53 Å) and one longer (2.54 Å) Sm–C bond lengths. There are three inequivalent Cr sites. In the first Cr site, Cr is bonded in a 1-coordinate geometry to one Sm, one Cr, and twelve Fe atoms. The Cr–Cr bond length is 2.15 Å. There are a spread of Cr–Fe bond distances ranging from 2.65–2.71 Å. In the second Cr site, Cr is bonded in a 1-coordinate geometry to one Sm, one Cr, and twelve Fe atoms. There are a spread of Cr–Fe bond distances ranging from 2.65–2.71 Å. In the third Cr site, Cr is bonded in a 1-coordinate geometry to one Sm and thirteen Fe atoms. There are a spread of Cr–Fe bond distances ranging from 2.32–2.75 Å. There are thirty-one inequivalent Fe sites. In the first Fe site, Fe is bonded to two Sm, one Cr, and nine Fe atoms to form distorted FeSm2CrFe9 cuboctahedra that share corners with seven FeSm2CrFe9 cuboctahedra, corners with two CSm2Fe4 octahedra, edges with four FeSm2Cr2Fe8 cuboctahedra, faces with seven FeSm2Cr2Fe8 cuboctahedra, and faces with two equivalent CSm2Fe4 octahedra. The corner-sharing octahedra tilt angles range from 45–46°. There are a spread of Fe–Fe bond distances ranging from 2.43–2.67 Å. In the second Fe site, Fe is bonded to two Sm, two Cr, and eight Fe atoms to form distorted FeSm2Cr2Fe8 cuboctahedra that share corners with seven FeSm2Cr2Fe8 cuboctahedra, corners with two CSm2Fe4 octahedra, edges with four FeSm2CrFe9 cuboctahedra, faces with seven FeSm2CrFe9 cuboctahedra, and faces with two equivalent CSm2Fe4 octahedra. The corner-sharing octahedra tilt angles range from 46–48°. There are four shorter (2.44 Å) and four longer (2.45 Å) Fe–Fe bond lengths. In the third Fe site, Fe is bonded to two Sm, one Cr, and nine Fe atoms to form distorted FeSm2CrFe9 cuboctahedra that share corners with six FeSm2CrFe9 cuboctahedra, corners with two CSm2Fe4 octahedra, edges with four FeSm2Cr2Fe8 cuboctahedra, faces with six FeSm2CrFe9 cuboctahedra, and faces with two equivalent CSm2Fe4 octahedra. The corner-sharing octahedra tilt angles range from 45–48°. There are a spread of Fe–Fe bond distances ranging from 2.42–2.67 Å. In the fourth Fe site, Fe is bonded to two Sm, two Cr, and eight Fe atoms to form distorted FeSm2Cr2Fe8 cuboctahedra that share corners with eight FeSm2Cr2Fe8 cuboctahedra, corners with two CSm2Fe4 octahedra, edges with four FeSm2CrFe9 cuboctahedra, faces with eight FeSm2Cr2Fe8 cuboctahedra, and faces with two equivalent CSm2Fe4 octahedra. The corner-sharing octahedral tilt angles are 46°. There are a spread of Fe–Fe bond distances ranging from 2.43–2.47 Å. In the fifth Fe site, Fe is bonded to two Sm, two Cr, and eight Fe atoms to form distorted FeSm2Cr2Fe8 cuboctahedra that share corners with fourteen FeSm2CrFe9 cuboctahedra, edges with two FeSm3CrFe8 cuboctahedra, faces with ten FeSm2Cr2Fe8 cuboctahedra, and faces with four CSm2Fe4 octahedra. There are a spread of Fe–Fe bond distances ranging from 2.42–2.47 Å. In the sixth Fe site, Fe is bonded in a 12-coordinate geometry to two Sm, one Cr, and nine Fe atoms. There are a spread of Fe–Fe bond distances ranging from 2.42–2.67 Å. In the seventh Fe site, Fe is bonded to three Sm, one Cr, and eight Fe atoms to form distorted FeSm3CrFe8 cuboctahedra that share corners with nine FeSm2CrFe9 cuboctahedra, corners with four CSm2Fe4 octahedra, edges with four FeSm2CrFe9 cuboctahedra, faces with eight FeSm2Cr2Fe8 cuboctahedra, and faces with two CSm2Fe4 octahedra. The corner-sharing octahedra tilt angles range from 63–70°. There are a spread of Fe–Fe bond distances ranging from 2.55–2.69 Å. In the eighth Fe site, Fe is bonded to three Sm, one Cr, and eight Fe atoms to form distorted FeSm3CrFe8 cuboctahedra that share corners with ten FeSm2Cr2Fe8 cuboctahedra, corners with four CSm2Fe4 octahedra, edges with three FeSm2Cr2Fe8 cuboctahedra, faces with seven FeSm2CrFe9 cuboctahedra, and faces with two CSm2Fe4 octahedra. The corner-sharing octahedra tilt angles range from 62–71°. There are a spread of Fe–Fe bond distances ranging from 2.56–2.68 Å. In the ninth Fe site, Fe is bonded in a single-bond geometry to one Cr, four Fe, and one C atom. There are one shorter (2.56 Å) and one longer (2.57 Å) Fe–Fe bond lengths. The Fe–C bond length is 1.91 Å. In the tenth Fe site, Fe is bonded in a single-bond geometry to one Cr, four Fe, and one C atom. There are one shorter (2.55 Å) and one longer (2.59 Å) Fe–Fe bond lengths. The Fe–C bond length is 1.91 Å. In the eleventh Fe site, Fe is bonded in a single-bond geometry to one Cr, four Fe, and one C atom. There are one shorter (2.56 Å) and one longer (2.59 Å) Fe–Fe bond lengths. The Fe–C bond length is 1.91 Å. In the twelfth Fe site, Fe is bonded in a single-bond geometry to one Cr, four Fe, and one C atom. Both Fe–Fe bond lengths are 2.56 Å. The Fe–C bond length is 1.91 Å. In the thirteenth Fe site, Fe is bonded to three Sm and nine Fe atoms to form distorted FeSm3Fe9 cuboctahedra that share corners with ten FeSm2CrFe9 cuboctahedra, corners with four CSm2Fe4 octahedra, edges with three FeSm2CrFe9 cuboctahedra, faces with seven FeSm2Cr2Fe8 cuboctahedra, and faces with two CSm2Fe4 octahedra. The corner-sharing octahedra tilt angles range from 62–69°. There are a spread of Fe–Fe bond distances ranging from 2.55–2.68 Å. In the fourteenth Fe site, Fe is bonded to three Sm, one Cr, and eight Fe atoms to form distorted FeSm3CrFe8 cuboctahedra that share corners with nine FeSm2Cr2Fe8 cuboctahedra, corners with four CSm2Fe4 octahedra, edges with four FeSm2Cr2Fe8 cuboctahedra, faces with eight FeSm2CrFe9 cuboctahedra, and faces with two CSm2Fe4 octahedra. The corner-sharing octahedra tilt angles range from 61–70°. There are a spread of Fe–Fe bond distances ranging from 2.56–2.69 Å. In the fifteenth Fe site, Fe is bonded in a single-bond geometry to one Cr, four Fe, and one C atom. The Fe–Fe bond length is 2.55 Å. The Fe–C bond length is 1.92 Å. In the sixteenth Fe site, Fe is bonded in a single-bond geometry to four Fe and one C atom. The Fe–Fe bond length is 2.55 Å. The Fe–C bond length is 1.91 Å. In the seventeenth Fe site, Fe is bonded in a single-bond geometry to four Fe and one C atom. The Fe–Fe bond length is 2.55 Å. The Fe–C bond length is 1.91 Å. In the eighteenth Fe site, Fe is bonded in a single-bond geometry to one Cr, four Fe, and one C atom. The Fe–Fe bond length is 2.55 Å. The Fe–C bond length is 1.91 Å. In the nineteenth Fe site, Fe is bonded in a single-bond geometry to one Cr, four Fe, and one C atom. The Fe–Fe bond length is 2.46 Å. The Fe–C bond length is 1.84 Å. In the twentieth Fe site, Fe is bonded in a single-bond geometry to two Cr, four Fe, and one C atom. The Fe–Fe bond length is 2.47 Å. The Fe–C bond length is 1.83 Å. In the twenty-first Fe site, Fe is bonded in a single-bond geometry to two Cr, four Fe, and one C atom. The Fe–Fe bond length is 2.47 Å. The Fe–C bond length is 1.85 Å. In the twenty-second Fe site, Fe is bonded in a single-bond geometry to one Cr, four Fe, and one C atom. The Fe–Fe bond length is 2.48 Å. The Fe–C bond length is 1.85 Å. In the twenty-third Fe site, Fe is bonded to two Sm, one Cr, and nine Fe atoms to form distorted FeSm2CrFe9 cuboctahedra that share corners with seven FeSm2Cr2Fe8 cuboctahedra, corners with four CSm2Fe4 octahedra, edges with three FeSm2CrFe9 cuboctahedra, edges with two CSm2Fe4 octahedra, and faces with seven FeSm2Cr2Fe8 cuboctahedra. The corner-sharing octahedra tilt angles range from 21–28°. There are a spread of Fe–Fe bond distances ranging from 2.46–2.69 Å. In the twenty-fourth Fe site, Fe is bonded to two Sm, two Cr, and eight Fe atoms to form distorted FeSm2Cr2Fe8 cuboctahedra that share corners with seven FeSm2Cr2Fe8 cuboctahedra, corners with four CSm2Fe4 octahedra, edges with three FeSm2Cr2Fe8 cuboctahedra, edges with two CSm2Fe4 octahedra, and faces with nine FeSm2CrFe9 cuboctahedra. The corner-sharing octahedra tilt angles range from 22–28°. There are one shorter (2.46 Å) and one longer (2.48 Å) Fe–Fe bond lengths. In the twenty-fifth Fe site, Fe is bonded in a single-bond geometry to one Cr, four Fe, and one C atom. The Fe–C bond length is 1.84 Å. In the twenty-sixth Fe site, Fe is bonded in a single-bond geometry to two Cr, four Fe, and one C atom. The Fe–C bond length is 1.85 Å. In the twenty-seventh Fe site, Fe is bonded to two Sm, two Cr, and eight Fe atoms to form distorted FeSm2Cr2Fe8 cuboctahedra that share corners with seven FeSm2Cr2Fe8 cuboctahedra, corners with four CSm2Fe4 octahedra, edges with three FeSm2CrFe9 cuboctahedra, edges with two CSm2Fe4 octahedra, and faces with nine FeSm2CrFe9 cuboctahedra. The corner-sharing octahedra tilt angles range from 22–28°. In the twenty-eighth Fe site, Fe is bonded to two Sm, one Cr, and nine Fe atoms to form distorted FeSm2CrFe9 cuboctahedra that share corners with seven FeSm2CrFe9 cuboctahedra, corners with four CSm2Fe4 octahedra, edges with three FeSm2Cr2Fe8 cuboctahedra, edges with two CSm2Fe4 octahedra, and faces with seven FeSm2Cr2Fe8 cuboctahedra. The corner-sharing octahedra tilt angles range from 22–28°. The Fe–Fe bond length is 2.69 Å. In the twenty-ninth Fe site, Fe is bonded in a single-bond geometry to two Cr, four Fe, and one C atom. The Fe–C bond length is 1.85 Å. In the thirtieth Fe site, Fe is bonded in a single-bond geometry to one Cr, four Fe, and one C atom. The Fe–C bond length is 1.85 Å. In the thirty-first Fe site, Fe is bonded in a distorted single-bond geometry to one Cr and six Fe atoms. There are four inequivalent C sites. In the first C site, C is bonded to two Sm and four Fe atoms to form CSm2Fe4 octahedra that share corners with ten FeSm2Cr2Fe8 cuboctahedra, corners with two CSm2Fe4 octahedra, edges with two FeSm2Cr2Fe8 cuboctahedra, and faces with six FeSm2Cr2Fe8 cuboctahedra. The corner-sharing octahedral tilt angles are 63°. In the second C site, C is bonded to two Sm and four Fe atoms to form CSm2Fe4 octahedra that share corners with ten FeSm2Cr2Fe8 cuboctahedra, corners with two CSm2Fe4 octahedra, edges with two FeSm2CrFe9 cuboctahedra, and faces with four FeSm2CrFe9 cuboctahedra. The corner-sharing octahedra tilt angles range from 63–64°. In the third C site, C is bonded to two Sm and four Fe atoms to form CSm2Fe4 octahedra that share corners with ten FeSm2Cr2Fe8 cuboctahedra, corners with two CSm2Fe4 octahedra, edges with two FeSm2Cr2Fe8 cuboctahedra, and faces with five FeSm2CrFe9 cuboctahedra. The corner-sharing octahedral tilt angles are 63°. In the fourth C site, C is bonded to two Sm and four Fe atoms to form CSm2Fe4 octahedra that share corners with ten FeSm2CrFe9 cuboctahedra, corners with two CSm2Fe4 octahedra, edges with two FeSm2CrFe9 cuboctahedra, and faces with five FeSm2Cr2Fe8 cuboctahedra. The corner-sharing octahedra tilt angles range from 63–64°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaCr2FeO10 by Materials Project

NaCr2FeO10 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Na is bonded in a 8-coordinate geometry to eight O atoms. There are a spread of Na–O bond distances ranging from 2.45–2.82 Å. Cr is bonded to four O atoms to form CrO4 tetrahedra that share corners with two equivalent FeO6 octahedra. The corner-sharing octahedra tilt angles range from 35–48°. There are a spread of Cr–O bond distances ranging from 1.62–1.74 Å. Fe is bonded to six O atoms to form FeO6 octahedra that share corners with four equivalent CrO4 tetrahedra. There are a spread of Fe–O bond distances ranging from 1.84–1.99 Å. There are five inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to one Fe atom. In the second O site, O is bonded in a distorted bent 150 degrees geometry to one Na, one Cr, and one Fe atom. In the third O site, O is bonded in a distorted trigonal planar geometry to one Na, one Cr, and one Fe atom. In the fourth O site, O is bonded in a distorted bent 150 degrees geometry to one Na and one Cr atom. In the fifth O site, O is bonded in a single-bond geometry to one Na and one Cr atom.

36 MATERIALS SCIENCE↗
DOE OSTI2025

1,10-Phenanthroline-Iron Complex-Derived Fe-N-C Electrocatalysts: Enhanced Oxygen Reduction Activity and Stability Through Synthesis Tuning

The development of electrocatalysts composed of earth-abundant elements is essential for advancing the commercial application of Proton Exchange Membrane Fuel Cells (PEMFC). Among these, single-atom electrocatalysts, such as Fe-N-C, show great promise for the oxygen reduction reaction (ORR). This study aims to improve the ORR activity and stability of Fe-N-C electrocatalysts by fine-tuning the straightforward 1,10-phenanthroline-iron complexation synthesis method. Key parameters, including iron-to-phenanthroline ratio, carbon powder surface area, and pyrolysis temperature were systematically varied to evaluate their influence on the resulting electrocatalysts. The findings of this study revealed that the electrocatalysts synthesized with 1,10-phenanthroline (Phen) and high-surface-area Black Pearls (BP) possessed much better ORR activity than electrocatalysts prepared by using Vulcan carbon (lower surface area). Interestingly, electrocatalysts prepared with BP, but with a non-bidentate nitrogen-containing ligand molecule, such as imidazole, showed a much poorer activity, as the resulting material predominantly consisted of inactive structures, such as encapsulated iron nanoparticles and iron oxide, as evidenced by HR-TEM, EXAFS, and XRD. Therefore, the results suggest that only the synergistic combination of the bidentate ligand phenanthroline (Phen) and the high-surface-area carbon support (BP) favored the formation of ORR-active Fe-N-C single-atom species upon pyrolysis. The study also unveiled a significant enhancement in electrocatalyst stability during accelerated durability tests (and air storage) as the pyrolysis temperature was increased from 700 to 1300 °C, albeit at the expense of ORR activity, likely resulting from the generation of iron particles. Pyrolysis at 1050 °C yielded the electrocatalyst with the most favorable balance of activity and stability in rotating disk measurements, while maintaining moderate durability under PEM fuel cell operation. The insights obtained in this study may guide the development of more active efficient and durable electrocatalysts, synthesized via a simple method using earth-abundant elements, for application in PEMFC cathodes.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2020

Materials Data on Sm4Fe34C3 by Materials Project

Sm4Fe34C3 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are two inequivalent Sm sites. In the first Sm site, Sm is bonded in a distorted bent 120 degrees geometry to nine Fe and two C atoms. There are a spread of Sm–Fe bond distances ranging from 3.06–3.41 Å. Both Sm–C bond lengths are 2.55 Å. In the second Sm site, Sm is bonded in a distorted single-bond geometry to fourteen Fe and one C atom. There are a spread of Sm–Fe bond distances ranging from 3.04–3.34 Å. The Sm–C bond length is 2.56 Å. There are eighteen inequivalent Fe sites. In the first Fe site, Fe is bonded in a single-bond geometry to five Fe and one C atom. There are a spread of Fe–Fe bond distances ranging from 2.47–2.66 Å. The Fe–C bond length is 1.91 Å. In the second Fe site, Fe is bonded in a single-bond geometry to seven Fe and one C atom. There are a spread of Fe–Fe bond distances ranging from 2.48–2.65 Å. The Fe–C bond length is 1.90 Å. In the third Fe site, Fe is bonded in a single-bond geometry to five Fe and one C atom. There are a spread of Fe–Fe bond distances ranging from 2.48–2.65 Å. The Fe–C bond length is 1.91 Å. In the fourth Fe site, Fe is bonded to three equivalent Sm and nine Fe atoms to form FeSm3Fe9 cuboctahedra that share corners with fourteen FeSm3Fe9 cuboctahedra, corners with two equivalent CSm2Fe4 octahedra, edges with seven FeSm3Fe9 cuboctahedra, faces with ten FeSm3Fe9 cuboctahedra, and a faceface with one CSm2Fe4 octahedra. The corner-sharing octahedra tilt angles range from 66–70°. There are a spread of Fe–Fe bond distances ranging from 2.48–2.67 Å. In the fifth Fe site, Fe is bonded to three equivalent Sm and nine Fe atoms to form distorted FeSm3Fe9 cuboctahedra that share corners with twelve FeSm3Fe9 cuboctahedra, corners with four CSm2Fe4 octahedra, edges with four FeSm3Fe9 cuboctahedra, faces with eight FeSm3Fe9 cuboctahedra, and faces with two CSm2Fe4 octahedra. The corner-sharing octahedra tilt angles range from 62–69°. There are a spread of Fe–Fe bond distances ranging from 2.48–2.68 Å. In the sixth Fe site, Fe is bonded to three equivalent Sm and nine Fe atoms to form FeSm3Fe9 cuboctahedra that share corners with thirteen FeSm3Fe9 cuboctahedra, corners with two equivalent CSm2Fe4 octahedra, edges with six FeSm3Fe9 cuboctahedra, faces with eleven FeSm3Fe9 cuboctahedra, and a faceface with one CSm2Fe4 octahedra. The corner-sharing octahedra tilt angles range from 66–70°. There are a spread of Fe–Fe bond distances ranging from 2.48–2.67 Å. In the seventh Fe site, Fe is bonded in a 2-coordinate geometry to one Sm and thirteen Fe atoms. There are a spread of Fe–Fe bond distances ranging from 2.38–2.77 Å. In the eighth Fe site, Fe is bonded in a 2-coordinate geometry to one Sm and thirteen Fe atoms. There are a spread of Fe–Fe bond distances ranging from 2.63–2.76 Å. In the ninth Fe site, Fe is bonded to two equivalent Sm and ten Fe atoms to form FeSm2Fe10 cuboctahedra that share corners with eight FeSm3Fe9 cuboctahedra, corners with two equivalent CSm2Fe4 octahedra, edges with four FeSm3Fe9 cuboctahedra, faces with eight FeSm3Fe9 cuboctahedra, and faces with two equivalent CSm2Fe4 octahedra. The corner-sharing octahedral tilt angles are 45°. There are two shorter (2.44 Å) and two longer (2.45 Å) Fe–Fe bond lengths. In the tenth Fe site, Fe is bonded to two equivalent Sm and ten Fe atoms to form FeSm2Fe10 cuboctahedra that share corners with ten FeSm3Fe9 cuboctahedra, corners with two equivalent CSm2Fe4 octahedra, edges with six FeSm3Fe9 cuboctahedra, and faces with ten FeSm3Fe9 cuboctahedra. The corner-sharing octahedral tilt angles are 44°. There are two shorter (2.43 Å) and two longer (2.44 Å) Fe–Fe bond lengths. In the eleventh Fe site, Fe is bonded to two Sm and ten Fe atoms to form distorted FeSm2Fe10 cuboctahedra that share corners with eleven FeSm3Fe9 cuboctahedra, a cornercorner with one CSm2Fe4 octahedra, edges with five FeSm3Fe9 cuboctahedra, faces with nine FeSm3Fe9 cuboctahedra, and faces with two equivalent CSm2Fe4 octahedra. The corner-sharing octahedral tilt angles are 45°. There are a spread of Fe–Fe bond distances ranging from 2.43–2.45 Å. In the twelfth Fe site, Fe is bonded to two Sm and ten Fe atoms to form distorted FeSm2Fe10 cuboctahedra that share corners with fifteen FeSm3Fe9 cuboctahedra, edges with three FeSm3Fe9 cuboctahedra, faces with eleven FeSm3Fe9 cuboctahedra, and faces with three CSm2Fe4 octahedra. There are a spread of Fe–Fe bond distances ranging from 2.42–2.44 Å. In the thirteenth Fe site, Fe is bonded in a single-bond geometry to seven Fe and one C atom. There are one shorter (2.47 Å) and one longer (2.49 Å) Fe–Fe bond lengths. The Fe–C bond length is 1.87 Å. In the fourteenth Fe site, Fe is bonded in a single-bond geometry to seven Fe and one C atom. The Fe–Fe bond length is 2.48 Å. The Fe–C bond length is 1.87 Å. In the fifteenth Fe site, Fe is bonded in a single-bond geometry to six Fe and one C atom. The Fe–Fe bond length is 2.47 Å. The Fe–C bond length is 1.87 Å. In the sixteenth Fe site, Fe is bonded in a 12-coordinate geometry to two equivalent Sm and ten Fe atoms. The Fe–Fe bond length is 2.50 Å. In the seventeenth Fe site, Fe is bonded to two equivalent Sm and ten Fe atoms to form distorted FeSm2Fe10 cuboctahedra that share corners with nine FeSm3Fe9 cuboctahedra, corners with four CSm2Fe4 octahedra, edges with three FeSm2Fe10 cuboctahedra, edges with two CSm2Fe4 octahedra, and faces with nine FeSm3Fe9 cuboctahedra. The corner-sharing octahedra tilt angles range from 21–29°. In the eighteenth Fe site, Fe is bonded to two equivalent Sm and ten Fe atoms to form distorted FeSm2Fe10 cuboctahedra that share corners with ten FeSm3Fe9 cuboctahedra, corners with two equivalent CSm2Fe4 octahedra, edges with four FeSm3Fe9 cuboctahedra, an edgeedge with one CSm2Fe4 octahedra, and faces with twelve FeSm3Fe9 cuboctahedra. The corner-sharing octahedra tilt angles range from 25–30°. There are two inequivalent C sites. In the first C site, C is bonded to two Sm and four Fe atoms to form CSm2Fe4 octahedra that share corners with twelve FeSm3Fe9 cuboctahedra, a cornercorner with one CSm2Fe4 octahedra, edges with two FeSm2Fe10 cuboctahedra, and faces with seven FeSm3Fe9 cuboctahedra. The corner-sharing octahedral tilt angles are 63°. In the second C site, C is bonded to two equivalent Sm and four Fe atoms to form CSm2Fe4 octahedra that share corners with ten FeSm3Fe9 cuboctahedra, corners with two equivalent CSm2Fe4 octahedra, edges with two equivalent FeSm2Fe10 cuboctahedra, and faces with six FeSm2Fe10 cuboctahedra. The corner-sharing octahedral tilt angles are 63°.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Dual active site tandem catalysis of metal hydroxyl oxides and single atoms for boosting oxygen evolution reaction

We report the high voltage in oxygen evolution reaction (OER) often causes structural change in electrocatalysts and forms multiple active sites. Therefore, exploring the synergy of various active sites is extremely significant to develop catalysts for OER with multiple elementary steps. Herein, we adopt the physically adsorbed metal ions method to successfully synthesize a highly-efficient electrocatalyst containing the dual active sites of Fe-NiOOH and NiC4 single atoms (marked as Ni SAs/Fe-NiOOH). The Ni SAs/Fe-NiOOH displays outstanding OER performance with an overpotential of 269 mV to deliver current density of 10 mA/cm 2 that shows 55 mV superior to commercial IrO 2 /CB at the same condition. Experiments and density functional theory calculations indicate that the excellent OER activity of Ni SAs/Fe-NiOOH catalyst is attributed to the synergy of dual active sites of NiC 4 SAs and Fe-NiOOH. A tandem catalysis mechanism is also proposed to reveal the synergism of two active centers, which makes the potential-determining step more facile and accordingly decreases the OER overpotential. This work offers a new concept of tandem catalysis to develop the electrocatalysts with many elemental steps, like OER and oxygen reduction reaction catalysts.

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

Materials Data on Tm4Fe34C3 by Materials Project

Tm4Fe34C3 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are two inequivalent Tm sites. In the first Tm site, Tm is bonded in a distorted bent 120 degrees geometry to nine Fe and two C atoms. There are a spread of Tm–Fe bond distances ranging from 3.01–3.35 Å. There are one shorter (2.48 Å) and one longer (2.49 Å) Tm–C bond lengths. In the second Tm site, Tm is bonded in a distorted single-bond geometry to fourteen Fe and one C atom. There are a spread of Tm–Fe bond distances ranging from 2.98–3.30 Å. The Tm–C bond length is 2.50 Å. There are eighteen inequivalent Fe sites. In the first Fe site, Fe is bonded in a single-bond geometry to five Fe and one C atom. There are a spread of Fe–Fe bond distances ranging from 2.45–2.64 Å. The Fe–C bond length is 1.91 Å. In the second Fe site, Fe is bonded in a single-bond geometry to seven Fe and one C atom. There are a spread of Fe–Fe bond distances ranging from 2.46–2.62 Å. The Fe–C bond length is 1.91 Å. In the third Fe site, Fe is bonded in a single-bond geometry to five Fe and one C atom. There are a spread of Fe–Fe bond distances ranging from 2.46–2.63 Å. The Fe–C bond length is 1.91 Å. In the fourth Fe site, Fe is bonded to three equivalent Tm and nine Fe atoms to form FeTm3Fe9 cuboctahedra that share corners with thirteen FeTm3Fe9 cuboctahedra, corners with two equivalent CTm2Fe4 octahedra, edges with seven FeTm3Fe9 cuboctahedra, faces with ten FeTm3Fe9 cuboctahedra, and a faceface with one CTm2Fe4 octahedra. The corner-sharing octahedra tilt angles range from 66–70°. There are a spread of Fe–Fe bond distances ranging from 2.45–2.65 Å. In the fifth Fe site, Fe is bonded to three equivalent Tm and nine Fe atoms to form FeTm3Fe9 cuboctahedra that share corners with ten FeTm3Fe9 cuboctahedra, corners with four CTm2Fe4 octahedra, edges with four FeTm3Fe9 cuboctahedra, faces with five FeTm3Fe9 cuboctahedra, and faces with two CTm2Fe4 octahedra. The corner-sharing octahedra tilt angles range from 63–69°. There are a spread of Fe–Fe bond distances ranging from 2.45–2.67 Å. In the sixth Fe site, Fe is bonded to three equivalent Tm and nine Fe atoms to form FeTm3Fe9 cuboctahedra that share corners with thirteen FeTm3Fe9 cuboctahedra, corners with two equivalent CTm2Fe4 octahedra, edges with six FeTm3Fe9 cuboctahedra, faces with ten FeTm3Fe9 cuboctahedra, and a faceface with one CTm2Fe4 octahedra. The corner-sharing octahedra tilt angles range from 65–69°. There are a spread of Fe–Fe bond distances ranging from 2.45–2.66 Å. In the seventh Fe site, Fe is bonded in a 2-coordinate geometry to one Tm and thirteen Fe atoms. There are a spread of Fe–Fe bond distances ranging from 2.39–2.78 Å. In the eighth Fe site, Fe is bonded in a 2-coordinate geometry to one Tm and thirteen Fe atoms. There are a spread of Fe–Fe bond distances ranging from 2.59–2.76 Å. In the ninth Fe site, Fe is bonded to two equivalent Tm and ten Fe atoms to form FeTm2Fe10 cuboctahedra that share corners with eight FeTm3Fe9 cuboctahedra, corners with two equivalent CTm2Fe4 octahedra, edges with two equivalent FeTm3Fe9 cuboctahedra, faces with six FeTm3Fe9 cuboctahedra, and faces with two equivalent CTm2Fe4 octahedra. The corner-sharing octahedral tilt angles are 44°. There are two shorter (2.43 Å) and two longer (2.44 Å) Fe–Fe bond lengths. In the tenth Fe site, Fe is bonded to two equivalent Tm and ten Fe atoms to form FeTm2Fe10 cuboctahedra that share corners with eight FeTm3Fe9 cuboctahedra, corners with two equivalent CTm2Fe4 octahedra, edges with six FeTm3Fe9 cuboctahedra, and faces with ten FeTm3Fe9 cuboctahedra. The corner-sharing octahedral tilt angles are 44°. There are two shorter (2.42 Å) and two longer (2.43 Å) Fe–Fe bond lengths. In the eleventh Fe site, Fe is bonded to two Tm and ten Fe atoms to form distorted FeTm2Fe10 cuboctahedra that share corners with ten FeTm3Fe9 cuboctahedra, a cornercorner with one CTm2Fe4 octahedra, edges with four FeTm3Fe9 cuboctahedra, faces with eight FeTm3Fe9 cuboctahedra, and faces with two equivalent CTm2Fe4 octahedra. The corner-sharing octahedral tilt angles are 44°. There are a spread of Fe–Fe bond distances ranging from 2.41–2.44 Å. In the twelfth Fe site, Fe is bonded to two Tm and ten Fe atoms to form distorted FeTm2Fe10 cuboctahedra that share corners with thirteen FeTm3Fe9 cuboctahedra, edges with three FeTm3Fe9 cuboctahedra, faces with nine FeTm3Fe9 cuboctahedra, and faces with three CTm2Fe4 octahedra. There are one shorter (2.40 Å) and three longer (2.43 Å) Fe–Fe bond lengths. In the thirteenth Fe site, Fe is bonded in a single-bond geometry to seven Fe and one C atom. The Fe–Fe bond length is 2.47 Å. The Fe–C bond length is 1.85 Å. In the fourteenth Fe site, Fe is bonded in a single-bond geometry to seven Fe and one C atom. There are one shorter (2.46 Å) and one longer (2.47 Å) Fe–Fe bond lengths. The Fe–C bond length is 1.85 Å. In the fifteenth Fe site, Fe is bonded in a single-bond geometry to six Fe and one C atom. The Fe–Fe bond length is 2.46 Å. The Fe–C bond length is 1.85 Å. In the sixteenth Fe site, Fe is bonded in a 12-coordinate geometry to two equivalent Tm and ten Fe atoms. The Fe–Fe bond length is 2.52 Å. In the seventeenth Fe site, Fe is bonded in a 12-coordinate geometry to two equivalent Tm and ten Fe atoms. In the eighteenth Fe site, Fe is bonded to two equivalent Tm and ten Fe atoms to form distorted FeTm2Fe10 cuboctahedra that share corners with nine FeTm3Fe9 cuboctahedra, corners with two equivalent CTm2Fe4 octahedra, edges with three FeTm3Fe9 cuboctahedra, an edgeedge with one CTm2Fe4 octahedra, and faces with twelve FeTm3Fe9 cuboctahedra. The corner-sharing octahedra tilt angles range from 25–30°. There are two inequivalent C sites. In the first C site, C is bonded to two Tm and four Fe atoms to form CTm2Fe4 octahedra that share corners with ten FeTm3Fe9 cuboctahedra, a cornercorner with one CTm2Fe4 octahedra, an edgeedge with one FeTm2Fe10 cuboctahedra, and faces with seven FeTm3Fe9 cuboctahedra. The corner-sharing octahedral tilt angles are 62°. In the second C site, C is bonded to two equivalent Tm and four Fe atoms to form CTm2Fe4 octahedra that share corners with six FeTm3Fe9 cuboctahedra, corners with two equivalent CTm2Fe4 octahedra, and faces with six FeTm2Fe10 cuboctahedra. The corner-sharing octahedral tilt angles are 62°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Gd4Fe34C3 by Materials Project

Gd4Fe34C3 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are two inequivalent Gd sites. In the first Gd site, Gd is bonded in a distorted bent 120 degrees geometry to nine Fe and two C atoms. There are a spread of Gd–Fe bond distances ranging from 3.03–3.39 Å. Both Gd–C bond lengths are 2.52 Å. In the second Gd site, Gd is bonded in a distorted single-bond geometry to fourteen Fe and one C atom. There are a spread of Gd–Fe bond distances ranging from 3.03–3.34 Å. The Gd–C bond length is 2.54 Å. There are eighteen inequivalent Fe sites. In the first Fe site, Fe is bonded to three equivalent Gd and nine Fe atoms to form distorted FeGd3Fe9 cuboctahedra that share corners with ten FeGd2Fe10 cuboctahedra, corners with four CGd2Fe4 octahedra, edges with four FeGd2Fe10 cuboctahedra, faces with five FeGd2Fe10 cuboctahedra, and faces with two CGd2Fe4 octahedra. The corner-sharing octahedra tilt angles range from 62–69°. There are a spread of Fe–Fe bond distances ranging from 2.46–2.65 Å. In the second Fe site, Fe is bonded to three equivalent Gd and nine Fe atoms to form FeGd3Fe9 cuboctahedra that share corners with thirteen FeGd2Fe10 cuboctahedra, corners with two equivalent CGd2Fe4 octahedra, edges with six FeGd2Fe10 cuboctahedra, faces with ten FeGd2Fe10 cuboctahedra, and a faceface with one CGd2Fe4 octahedra. The corner-sharing octahedra tilt angles range from 65–70°. There are a spread of Fe–Fe bond distances ranging from 2.46–2.66 Å. In the third Fe site, Fe is bonded in a single-bond geometry to five Fe and one C atom. There are a spread of Fe–Fe bond distances ranging from 2.46–2.64 Å. The Fe–C bond length is 1.90 Å. In the fourth Fe site, Fe is bonded in a single-bond geometry to seven Fe and one C atom. There are a spread of Fe–Fe bond distances ranging from 2.47–2.65 Å. The Fe–C bond length is 1.90 Å. In the fifth Fe site, Fe is bonded in a single-bond geometry to five Fe and one C atom. There are a spread of Fe–Fe bond distances ranging from 2.46–2.63 Å. The Fe–C bond length is 1.90 Å. In the sixth Fe site, Fe is bonded to three equivalent Gd and nine Fe atoms to form FeGd3Fe9 cuboctahedra that share corners with thirteen FeGd2Fe10 cuboctahedra, corners with two equivalent CGd2Fe4 octahedra, edges with seven FeGd2Fe10 cuboctahedra, faces with ten FeGd2Fe10 cuboctahedra, and a faceface with one CGd2Fe4 octahedra. The corner-sharing octahedra tilt angles range from 66–70°. There are a spread of Fe–Fe bond distances ranging from 2.47–2.68 Å. In the seventh Fe site, Fe is bonded in a 2-coordinate geometry to one Gd and thirteen Fe atoms. There are a spread of Fe–Fe bond distances ranging from 2.39–2.74 Å. In the eighth Fe site, Fe is bonded in a 2-coordinate geometry to one Gd and thirteen Fe atoms. There are a spread of Fe–Fe bond distances ranging from 2.62–2.74 Å. In the ninth Fe site, Fe is bonded in a single-bond geometry to seven Fe and one C atom. There are a spread of Fe–Fe bond distances ranging from 2.41–2.46 Å. The Fe–C bond length is 1.85 Å. In the tenth Fe site, Fe is bonded in a single-bond geometry to seven Fe and one C atom. There are a spread of Fe–Fe bond distances ranging from 2.43–2.46 Å. The Fe–C bond length is 1.85 Å. In the eleventh Fe site, Fe is bonded in a single-bond geometry to six Fe and one C atom. There are two shorter (2.43 Å) and one longer (2.46 Å) Fe–Fe bond lengths. The Fe–C bond length is 1.85 Å. In the twelfth Fe site, Fe is bonded in a 12-coordinate geometry to two equivalent Gd and ten Fe atoms. There are a spread of Fe–Fe bond distances ranging from 2.41–2.47 Å. In the thirteenth Fe site, Fe is bonded in a 12-coordinate geometry to two equivalent Gd and ten Fe atoms. Both Fe–Fe bond lengths are 2.42 Å. In the fourteenth Fe site, Fe is bonded to two equivalent Gd and ten Fe atoms to form distorted FeGd2Fe10 cuboctahedra that share corners with nine FeGd2Fe10 cuboctahedra, corners with two equivalent CGd2Fe4 octahedra, edges with three FeGd2Fe10 cuboctahedra, an edgeedge with one CGd2Fe4 octahedra, and faces with twelve FeGd2Fe10 cuboctahedra. The corner-sharing octahedra tilt angles range from 25–30°. There are one shorter (2.42 Å) and one longer (2.43 Å) Fe–Fe bond lengths. In the fifteenth Fe site, Fe is bonded to two equivalent Gd and ten Fe atoms to form FeGd2Fe10 cuboctahedra that share corners with eight FeGd2Fe10 cuboctahedra, corners with two equivalent CGd2Fe4 octahedra, edges with two equivalent FeGd3Fe9 cuboctahedra, faces with six FeGd2Fe10 cuboctahedra, and faces with two equivalent CGd2Fe4 octahedra. The corner-sharing octahedral tilt angles are 45°. In the sixteenth Fe site, Fe is bonded to two equivalent Gd and ten Fe atoms to form FeGd2Fe10 cuboctahedra that share corners with eight FeGd2Fe10 cuboctahedra, corners with two equivalent CGd2Fe4 octahedra, edges with six FeGd3Fe9 cuboctahedra, and faces with ten FeGd2Fe10 cuboctahedra. The corner-sharing octahedral tilt angles are 45°. In the seventeenth Fe site, Fe is bonded to two Gd and ten Fe atoms to form distorted FeGd2Fe10 cuboctahedra that share corners with ten FeGd2Fe10 cuboctahedra, a cornercorner with one CGd2Fe4 octahedra, edges with four FeGd3Fe9 cuboctahedra, faces with eight FeGd2Fe10 cuboctahedra, and faces with two equivalent CGd2Fe4 octahedra. The corner-sharing octahedral tilt angles are 45°. In the eighteenth Fe site, Fe is bonded to two Gd and ten Fe atoms to form distorted FeGd2Fe10 cuboctahedra that share corners with thirteen FeGd2Fe10 cuboctahedra, edges with three FeGd3Fe9 cuboctahedra, faces with nine FeGd2Fe10 cuboctahedra, and faces with three CGd2Fe4 octahedra. There are two inequivalent C sites. In the first C site, C is bonded to two Gd and four Fe atoms to form CGd2Fe4 octahedra that share corners with ten FeGd2Fe10 cuboctahedra, a cornercorner with one CGd2Fe4 octahedra, an edgeedge with one FeGd2Fe10 cuboctahedra, and faces with seven FeGd2Fe10 cuboctahedra. The corner-sharing octahedral tilt angles are 63°. In the second C site, C is bonded to two equivalent Gd and four Fe atoms to form CGd2Fe4 octahedra that share corners with six FeGd2Fe10 cuboctahedra, corners with two equivalent CGd2Fe4 octahedra, and faces with six FeGd2Fe10 cuboctahedra. The corner-sharing octahedral tilt angles are 63°.

36 MATERIALS SCIENCE↗