Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Mn-N”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

11 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Promoting Atomically Dispersed MnN 4 Sites via Sulfur Doping for Oxygen Reduction: Unveiling Intrinsic Activity and Degradation in Fuel Cells

Carbon supported and nitrogen coordinated single Mn site catalysts (Mn-N-C) catalysts are the most desirable platinum group metal (PGM)-free cathode catalysts for proton exchange membrane fuel cells (PEMFCs) due to their insignificant Fenton reactions (vs. Fe), earth abundances (vs. Co) and encouraging activity and stability. However, current Mn-N-C catalysts suffer from high over-potential due to low intrinsic activity and less dense MnN 4 sites. Herein, we present sulfur-doped Mn-N-C catalyst (Mn-N-C-S) synthesized through an effective adsorption-pyrolysis process. Using electron microscopy and X-ray absorption spectroscopy (XAS) techniques, we verify the uniform dispersion of MnN 4 sites and confirm the effect of S doping on the Mn-N coordination. The Mn-N-C-S catalyst exhibits a favorable oxygen reduction reaction (ORR) activity in acidic media relative to the S-free Mn-N-C catalyst. The corresponding membrane electrode assembly (MEA) generated a remarkable performance with a peak power density of 500 mW cm -2 under a realistic H 2 /air environment. The constant voltage tests of fuel cells confirm the much-enhanced stability of the Mn-N-C-S catalyst compared to the Fe-N-C and Fe-N-C-S catalysts. The electron microscopy and Fourier transform XAS analysis provide insights into catalyst degradation associated with Mn oxidation and agglomeration. The theoretical calculation elucidates that the promoted ORR activity is mainly attributed to the spatial effect stemmed from the repulsive interaction between the ORR intermediates and adjacent S do-pants.

25 ENERGY STORAGE↗
DOE OSTI2020

Materials Data on Mn3N2 by Materials Project

Mn3N2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent Mn2+ sites. In the first Mn2+ site, Mn2+ is bonded to five equivalent N3- atoms to form a mixture of corner and edge-sharing MnN5 square pyramids. There are four shorter (2.03 Å) and one longer (2.06 Å) Mn–N bond lengths. In the second Mn2+ site, Mn2+ is bonded in a linear geometry to two equivalent N3- atoms. Both Mn–N bond lengths are 1.93 Å. N3- is bonded to six Mn2+ atoms to form a mixture of corner and edge-sharing NMn6 octahedra. The corner-sharing octahedra tilt angles range from 0–6°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mn4N by Materials Project

Mn4N crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. there are two inequivalent Mn sites. In the first Mn site, Mn is bonded to twelve equivalent Mn atoms to form MnMn12 cuboctahedra that share corners with twelve equivalent MnMn12 cuboctahedra, faces with six equivalent MnMn12 cuboctahedra, and faces with eight equivalent NMn6 octahedra. All Mn–Mn bond lengths are 2.66 Å. In the second Mn site, Mn is bonded in a linear geometry to four equivalent Mn and two equivalent N atoms. Both Mn–N bond lengths are 1.88 Å. N is bonded to six equivalent Mn atoms to form NMn6 octahedra that share corners with six equivalent NMn6 octahedra and faces with eight equivalent MnMn12 cuboctahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mn3N2 by Materials Project

Mn3N2 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are two inequivalent Mn2+ sites. In the first Mn2+ site, Mn2+ is bonded in a distorted trigonal non-coplanar geometry to four equivalent N3- atoms. There are three shorter (1.84 Å) and one longer (2.48 Å) Mn–N bond lengths. In the second Mn2+ site, Mn2+ is bonded to six equivalent N3- atoms to form edge-sharing MnN6 octahedra. There are two shorter (2.25 Å) and four longer (2.28 Å) Mn–N bond lengths. N3- is bonded in a 3-coordinate geometry to seven Mn2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mn4N by Materials Project

Mn4N crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional and consists of one ammonia molecule and one Mn framework. In the Mn framework, there are four inequivalent Mn sites. In the first Mn site, Mn is bonded to six Mn atoms to form corner-sharing MnMn6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (2.16 Å) and two longer (2.17 Å) Mn–Mn bond lengths. In the second Mn site, Mn is bonded in a linear geometry to two equivalent Mn atoms. In the third Mn site, Mn is bonded in a linear geometry to two equivalent Mn atoms. In the fourth Mn site, Mn is bonded in a linear geometry to two equivalent Mn atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MnN by Materials Project

MnN is Halite, Rock Salt structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Mn3+ is bonded to six equivalent N3- atoms to form a mixture of corner and edge-sharing MnN6 octahedra. The corner-sharing octahedral tilt angles are 0°. All Mn–N bond lengths are 2.07 Å. N3- is bonded to six equivalent Mn3+ atoms to form a mixture of corner and edge-sharing NMn6 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mn2N by Materials Project

Mn2N is zeta iron carbide-like structured and crystallizes in the orthorhombic Pbcn space group. The structure is three-dimensional. Mn is bonded in a distorted trigonal planar geometry to three equivalent N atoms. There are a spread of Mn–N bond distances ranging from 1.93–1.96 Å. N is bonded to six equivalent Mn atoms to form a mixture of edge and corner-sharing NMn6 octahedra. The corner-sharing octahedra tilt angles range from 49–50°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MnN by Materials Project

MnN crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are two inequivalent Mn3+ sites. In the first Mn3+ site, Mn3+ is bonded to five N3- atoms to form distorted MnN5 trigonal bipyramids that share corners with six equivalent MnN4 tetrahedra, corners with four equivalent MnN5 trigonal bipyramids, edges with two equivalent MnN4 tetrahedra, and edges with four equivalent MnN5 trigonal bipyramids. There are a spread of Mn–N bond distances ranging from 1.90–2.17 Å. In the second Mn3+ site, Mn3+ is bonded to four N3- atoms to form MnN4 tetrahedra that share corners with four equivalent MnN4 tetrahedra, corners with six equivalent MnN5 trigonal bipyramids, and edges with two equivalent MnN5 trigonal bipyramids. There are a spread of Mn–N bond distances ranging from 1.74–1.96 Å. There are two inequivalent N3- sites. In the first N3- site, N3- is bonded in a distorted trigonal planar geometry to three Mn3+ atoms. In the second N3- site, N3- is bonded in a 6-coordinate geometry to six Mn3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MnN by Materials Project

MnN is Tetraauricupride structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Mn3+ is bonded in a body-centered cubic geometry to eight equivalent N3- atoms. All Mn–N bond lengths are 2.19 Å. N3- is bonded in a body-centered cubic geometry to eight equivalent Mn3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MnN by Materials Project

MnN is Zincblende, Sphalerite structured and crystallizes in the cubic F-43m space group. The structure is three-dimensional. Mn3+ is bonded to four equivalent N3- atoms to form corner-sharing MnN4 tetrahedra. All Mn–N bond lengths are 1.84 Å. N3- is bonded to four equivalent Mn3+ atoms to form corner-sharing NMn4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mn3N4 by Materials Project

Mn3N4 is Corundum-like structured and crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are three inequivalent Mn4+ sites. In the first Mn4+ site, Mn4+ is bonded to six N3- atoms to form MnN6 octahedra that share corners with four equivalent MnN6 octahedra, corners with two equivalent MnN4 tetrahedra, edges with four MnN6 octahedra, and edges with two equivalent MnN4 tetrahedra. The corner-sharing octahedra tilt angles range from 49–51°. There is two shorter (1.95 Å) and four longer (2.00 Å) Mn–N bond length. In the second Mn4+ site, Mn4+ is bonded to six N3- atoms to form MnN6 octahedra that share corners with eight MnN6 octahedra, corners with four equivalent MnN4 tetrahedra, edges with two equivalent MnN6 octahedra, and an edgeedge with one MnN4 tetrahedra. The corner-sharing octahedra tilt angles range from 47–51°. There are a spread of Mn–N bond distances ranging from 1.96–2.02 Å. In the third Mn4+ site, Mn4+ is bonded to four N3- atoms to form a mixture of corner and edge-sharing MnN4 tetrahedra. The corner-sharing octahedra tilt angles range from 58–62°. There is one shorter (1.77 Å) and three longer (1.79 Å) Mn–N bond length. There are three inequivalent N3- sites. In the first N3- site, N3- is bonded to four Mn4+ atoms to form distorted corner-sharing NMn4 trigonal pyramids. In the second N3- site, N3- is bonded in a rectangular see-saw-like geometry to four Mn4+ atoms. In the third N3- site, N3- is bonded in a rectangular see-saw-like geometry to four Mn4+ atoms.

36 MATERIALS SCIENCE↗