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38 records · Page 3

Materials Data on CuAg2(NO3)4 by Materials Project

Ag2Cu(NO3)4 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are two inequivalent Ag1+ sites. In the first Ag1+ site, Ag1+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ag–O bond distances ranging from 2.48–2.97 Å. In the second Ag1+ site, Ag1+ is bonded in a 6-coordinate geometry to seven O2- atoms. There are a spread of Ag–O bond distances ranging from 2.41–2.96 Å. There are two inequivalent Cu2+ sites. In the first Cu2+ site, Cu2+ is bonded in a square co-planar geometry to four O2- atoms. There are two shorter (1.99 Å) and two longer (2.02 Å) Cu–O bond lengths. In the second Cu2+ site, Cu2+ is bonded in a square co-planar geometry to four O2- atoms. All Cu–O bond lengths are 2.01 Å. There are four inequivalent N5+ sites. In the first N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of N–O bond distances ranging from 1.25–1.30 Å. In the second N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of N–O bond distances ranging from 1.24–1.32 Å. In the third N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of N–O bond distances ranging from 1.24–1.31 Å. In the fourth N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. There is two shorter (1.25 Å) and one longer (1.32 Å) N–O bond length. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to one Ag1+, one Cu2+, and one N5+ atom. In the second O2- site, O2- is bonded in a distorted single-bond geometry to one Ag1+ and one N5+ atom. In the third O2- site, O2- is bonded in a distorted single-bond geometry to two Ag1+ and one N5+ atom. In the fourth O2- site, O2- is bonded in a distorted water-like geometry to one Ag1+, one Cu2+, and one N5+ atom. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent Ag1+ and one N5+ atom. In the sixth O2- site, O2- is bonded in a distorted water-like geometry to one Ag1+ and one N5+ atom. In the seventh O2- site, O2- is bonded in a 3-coordinate geometry to one Ag1+, one Cu2+, and one N5+ atom. In the eighth O2- site, O2- is bonded in a distorted single-bond geometry to two Ag1+ and one N5+ atom. In the ninth O2- site, O2- is bonded in a distorted single-bond geometry to one Ag1+ and one N5+ atom. In the tenth O2- site, O2- is bonded in a 3-coordinate geometry to one Ag1+, one Cu2+, and one N5+ atom. In the eleventh O2- site, O2- is bonded in a 2-coordinate geometry to one Ag1+ and one N5+ atom. In the twelfth O2- site, O2- is bonded in a distorted single-bond geometry to one Ag1+ and one N5+ atom.

36 MATERIALS SCIENCE↗

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↗