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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Synthesis of High Surface Area VS2 for Nitrogen Reduction

Ammonia synthesis from dinitrogen provides a critical chemical feedstock to agriculture worldwide. The dominant process for ammonia synthesis is the Haber-Bosch process, which is fossil-fuel dependent and energy intensive. The electrochemical nitrogen reduction reaction (NRR) could provide a more environmentally friendly route to industrial ammonia synthesis. We have worked to realize electrochemical NRR by developing transition metal dichalcogenide NRR catalysts. In the first part of this presentation, a VS2-based NRR electrocatalyst, which has shown promising activity and selectivity, will be presented. The synthesis of this VS2-based catalyst is straightforward and results in few-layer VS2 or VSx, (x < 2) nanoflakes. Additionally, the proposed mechanism of NRR on VS2 will be discussed, and we will discuss DFT simulation of NRR on VS2 and MoS2 as well as planned in-situ Raman experiments to probe this mechanism. In the second part of this presentation, we will share several lessons learned during our early NRR research including important points of electrochemical cell design and experimental controls to reduce environmental ammonia contamination of experiments. Finally, we will address areas of opportunity for electrochemical NRR.

dichalcogenide↗
DOE OSTI2020

Materials Data on VS2 by Materials Project

VS2 is trigonal omega-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is two-dimensional and consists of two VS2 sheets oriented in the (0, 0, 1) direction. V4+ is bonded to six equivalent S2- atoms to form edge-sharing VS6 octahedra. All V–S bond lengths are 2.36 Å. S2- is bonded in a distorted T-shaped geometry to three equivalent V4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on VS2 by Materials Project

VS2 is trigonal omega-like structured and crystallizes in the triclinic P-1 space group. The structure is two-dimensional and consists of one VS2 sheet oriented in the (0, 0, 1) direction. V4+ is bonded to six equivalent S2- atoms to form edge-sharing VS6 octahedra. All V–S bond lengths are 2.35 Å. S2- is bonded in a distorted T-shaped geometry to three equivalent V4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on VS2 by Materials Project

VS2 crystallizes in the monoclinic P2/m space group. The structure is one-dimensional and consists of one VS2 ribbon oriented in the (1, 0, 0) direction. V4+ is bonded in a square co-planar geometry to four equivalent S2- atoms. All V–S bond lengths are 2.25 Å. S2- is bonded in an L-shaped geometry to two equivalent V4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on VS2 by Materials Project

VS2 is trigonal omega structured and crystallizes in the trigonal P-3m1 space group. The structure is two-dimensional and consists of one VS2 sheet oriented in the (0, 0, 1) direction. V4+ is bonded to six equivalent S2- atoms to form edge-sharing VS6 octahedra. All V–S bond lengths are 2.36 Å. S2- is bonded in a distorted T-shaped geometry to three equivalent V4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on VS2 by Materials Project

VS2 is trigonal omega-like structured and crystallizes in the trigonal R-3m space group. The structure is two-dimensional and consists of three VS2 sheets oriented in the (0, 0, 1) direction. V4+ is bonded to six equivalent S2- atoms to form edge-sharing VS6 octahedra. All V–S bond lengths are 2.36 Å. S2- is bonded in a 3-coordinate geometry to three equivalent V4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on VS2 by Materials Project

VS2 is Molybdenite structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is two-dimensional and consists of two VS2 sheets oriented in the (0, 0, 1) direction. V4+ is bonded to six equivalent S2- atoms to form distorted edge-sharing VS6 pentagonal pyramids. All V–S bond lengths are 2.37 Å. S2- is bonded in a 3-coordinate geometry to three equivalent V4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on VS2 by Materials Project

VS2 is trigonal omega-like structured and crystallizes in the trigonal R-3m space group. The structure is two-dimensional and consists of three VS2 sheets oriented in the (0, 0, 1) direction. V4+ is bonded to six equivalent S2- atoms to form edge-sharing VS6 octahedra. All V–S bond lengths are 2.36 Å. S2- is bonded in a distorted T-shaped geometry to three equivalent V4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on VS2 by Materials Project

VS2 crystallizes in the triclinic P1 space group. The structure is two-dimensional and consists of one vanadium molecule and two S sheets oriented in the (0, 0, 1) direction. In each S sheet, S2- is bonded in a hexagonal planar geometry to six equivalent S2- atoms. There are a spread of S–S bond distances ranging from 2.55–2.60 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on VS2 by Materials Project

VS2 crystallizes in the triclinic P1 space group. The structure is two-dimensional and consists of one vanadium dust molecule and two S sheets oriented in the (0, 0, 1) direction. In each S sheet, S2- is bonded in a square co-planar geometry to four equivalent S2- atoms. There are two shorter (2.30 Å) and two longer (2.39 Å) S–S bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na(VS2)2 by Materials Project

Na(VS2)2 crystallizes in the monoclinic Pm space group. The structure is three-dimensional. Na1+ is bonded in a 6-coordinate geometry to six S2- atoms. There are a spread of Na–S bond distances ranging from 2.86–2.93 Å. There are two inequivalent V+3.50+ sites. In the first V+3.50+ site, V+3.50+ is bonded to six S2- atoms to form edge-sharing VS6 octahedra. There are a spread of V–S bond distances ranging from 2.34–2.48 Å. In the second V+3.50+ site, V+3.50+ is bonded to six S2- atoms to form edge-sharing VS6 octahedra. There are a spread of V–S bond distances ranging from 2.32–2.48 Å. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded to two equivalent Na1+ and three V+3.50+ atoms to form a mixture of distorted edge and corner-sharing SNa2V3 square pyramids. In the second S2- site, S2- is bonded to two equivalent Na1+ and three V+3.50+ atoms to form a mixture of distorted edge and corner-sharing SNa2V3 trigonal bipyramids. In the third S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to one Na1+ and three V+3.50+ atoms. In the fourth S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to one Na1+ and three V+3.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg(VS2)4 by Materials Project

Mg(VS2)4 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Mg2+ is bonded to six equivalent S2- atoms to form MgS6 octahedra that share corners with six equivalent VS6 octahedra and edges with six equivalent VS6 octahedra. The corner-sharing octahedral tilt angles are 5°. All Mg–S bond lengths are 2.57 Å. There are two inequivalent V+3.50+ sites. In the first V+3.50+ site, V+3.50+ is bonded to six S2- atoms to form VS6 octahedra that share edges with two equivalent MgS6 octahedra and edges with six VS6 octahedra. There are two shorter (2.37 Å) and four longer (2.39 Å) V–S bond lengths. In the second V+3.50+ site, V+3.50+ is bonded to six equivalent S2- atoms to form VS6 octahedra that share corners with six equivalent MgS6 octahedra and edges with six equivalent VS6 octahedra. The corner-sharing octahedral tilt angles are 5°. All V–S bond lengths are 2.38 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three V+3.50+ atoms. In the second S2- site, S2- is bonded in a distorted T-shaped geometry to three equivalent V+3.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on VS2 by Materials Project

VS2 is trigonal omega-like structured and crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. V4+ is bonded to six equivalent S2- atoms to form edge-sharing VS6 octahedra. All V–S bond lengths are 2.36 Å. S2- is bonded in a distorted T-shaped geometry to three equivalent V4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(VS2)4 by Materials Project

Ca(VS2)4 is beta indium sulfide-derived structured and crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Ca2+ is bonded in a 6-coordinate geometry to six equivalent S2- atoms. All Ca–S bond lengths are 2.79 Å. There are two inequivalent V+3.50+ sites. In the first V+3.50+ site, V+3.50+ is bonded to six S2- atoms to form edge-sharing VS6 octahedra. There are two shorter (2.37 Å) and four longer (2.39 Å) V–S bond lengths. In the second V+3.50+ site, V+3.50+ is bonded to six equivalent S2- atoms to form edge-sharing VS6 octahedra. All V–S bond lengths are 2.37 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three V+3.50+ atoms. In the second S2- site, S2- is bonded in a distorted T-shaped geometry to three equivalent V+3.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on VS2 by Materials Project

VS2 crystallizes in the tetragonal I-42d space group. The structure is three-dimensional. V4+ is bonded to four equivalent S2- atoms to form corner-sharing VS4 tetrahedra. All V–S bond lengths are 2.22 Å. S2- is bonded in a bent 120 degrees geometry to two equivalent V4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li3(VS2)4 by Materials Project

Li3(VS2)4 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are two inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded in a rectangular see-saw-like geometry to four S2- atoms. There are a spread of Li–S bond distances ranging from 2.39–2.44 Å. In the second Li1+ site, Li1+ is bonded in a rectangular see-saw-like geometry to four S2- atoms. There are one shorter (2.39 Å) and three longer (2.43 Å) Li–S bond lengths. There are three inequivalent V+3.25+ sites. In the first V+3.25+ site, V+3.25+ is bonded to six S2- atoms to form edge-sharing VS6 octahedra. There are a spread of V–S bond distances ranging from 2.32–2.46 Å. In the second V+3.25+ site, V+3.25+ is bonded to six S2- atoms to form edge-sharing VS6 octahedra. There are a spread of V–S bond distances ranging from 2.29–2.56 Å. In the third V+3.25+ site, V+3.25+ is bonded to six S2- atoms to form edge-sharing VS6 octahedra. There are a spread of V–S bond distances ranging from 2.30–2.56 Å. There are six inequivalent S2- sites. In the first S2- site, S2- is bonded in a 6-coordinate geometry to three Li1+ and three V+3.25+ atoms. In the second S2- site, S2- is bonded in a 5-coordinate geometry to two equivalent Li1+ and three V+3.25+ atoms. In the third S2- site, S2- is bonded to one Li1+ and three V+3.25+ atoms to form distorted corner-sharing SLiV3 trigonal pyramids. In the fourth S2- site, S2- is bonded in a 5-coordinate geometry to two Li1+ and three V+3.25+ atoms. In the fifth S2- site, S2- is bonded to one Li1+ and three V+3.25+ atoms to form distorted corner-sharing SLiV3 trigonal pyramids. In the sixth S2- site, S2- is bonded in a 3-coordinate geometry to three V+3.25+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TiTl(VS2)4 by Materials Project

TiTl(VS2)4 is Orthorhombic Perovskite-derived structured and crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Ti4+ is bonded to six S2- atoms to form TiS6 octahedra that share corners with four equivalent VS6 octahedra, edges with four equivalent TlS10 cuboctahedra, edges with two equivalent TiS6 octahedra, and edges with four equivalent VS6 octahedra. The corner-sharing octahedral tilt angles are 46°. There are four shorter (2.44 Å) and two longer (2.46 Å) Ti–S bond lengths. There are two inequivalent V+2.75+ sites. In the first V+2.75+ site, V+2.75+ is bonded to six S2- atoms to form VS6 octahedra that share corners with four equivalent TlS10 cuboctahedra, corners with two equivalent TiS6 octahedra, corners with four equivalent VS6 octahedra, edges with four equivalent VS6 octahedra, a faceface with one TlS10 cuboctahedra, and a faceface with one VS6 octahedra. The corner-sharing octahedra tilt angles range from 46–52°. There are a spread of V–S bond distances ranging from 2.29–2.51 Å. In the second V+2.75+ site, V+2.75+ is bonded to six S2- atoms to form VS6 octahedra that share corners with three equivalent TlS10 cuboctahedra, corners with four equivalent VS6 octahedra, an edgeedge with one TlS10 cuboctahedra, edges with two equivalent TiS6 octahedra, edges with four equivalent VS6 octahedra, and a faceface with one VS6 octahedra. The corner-sharing octahedra tilt angles range from 49–52°. There are a spread of V–S bond distances ranging from 2.32–2.56 Å. Tl1+ is bonded to ten S2- atoms to form distorted TlS10 cuboctahedra that share corners with fourteen VS6 octahedra, edges with two equivalent VS6 octahedra, edges with four equivalent TiS6 octahedra, faces with two equivalent TlS10 cuboctahedra, and faces with two equivalent VS6 octahedra. The corner-sharing octahedra tilt angles range from 11–41°. There are a spread of Tl–S bond distances ranging from 3.25–3.39 Å. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded in a 3-coordinate geometry to three equivalent V+2.75+ and two equivalent Tl1+ atoms. In the second S2- site, S2- is bonded to five V+2.75+ atoms to form distorted edge-sharing SV5 trigonal bipyramids. In the third S2- site, S2- is bonded in a 3-coordinate geometry to one Ti4+, two equivalent V+2.75+, and two equivalent Tl1+ atoms. In the fourth S2- site, S2- is bonded in a 4-coordinate geometry to two equivalent Ti4+, two V+2.75+, and one Tl1+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Nitrate-To-Ammonia Electroconversion at Neutral pH on Polycrystalline Vanadium Sulfide Derived from Vanadium Disulfide

The electrochemical nitrate reduction reaction (NO3RR) offers a pathway to produce NH3 for fuel and fertilizer from waste NO3-. In this work, a polycrystalline vanadium sulfide (VSx), which is derived from solvothermally grown and annealed VS2, is shown to exhibit excellent NO3RR activity (2.3 +- 0.6 mg.cm-2 geo..h-1 @ -0.92 VRHE) and Faradaic efficiency to NH4+ (69 +- 6% at -0.69 VRHE) in buffered neutral pH electrolyte containing 0.1 M NO3-. A variety of characterization techniques are leveraged to support the VSx assignment, including X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure spectroscopy, selected area electron diffraction, and X-ray diffraction measurements. The VS2 annealing step reduces the oxide character and generates VSx, which, based on the improved NO3RR activity, results in the creation of active sites for NO3- binding. To help shed light on NO3RR on VSx, VS2 is used as a model system, and a grand-canonical density functional theory (GC-DFT) investigation of VS2 shows strong evidence that S vacancies are active sites for NO3RR, where NO3- outcompetes H+ for adsorption at the S-vacancy sites. Moreover, GC-DFT results highlight a thermodynamically favorable reaction to generate NH4+ in an aqueous electrolyte at relevant cathodic potentials. As an annealed material, VSx may contain undersaturated V sites, which show an electronic structure similar to the theoretically calculated S-vacancy site of VS2, and these sites may contribute to the observed increase in NO3RR activity and selectivity for NH4+ on VSx versus unannealed VS2. Finally, kinetic isotope effect measurements suggest that the kinetic rate-limiting step of the NO3RR on VSx is not proton-coupled, indicating it may be the first electron transfer to adsorbed NO3*.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗