New Compounds and Phase Selection of Nickel Sulfides via Oxidation State Control in Molten Hydroxides
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Univ. of Illinois, Chicago, IL (United States)
- Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
- Argonne National Lab. (ANL), Argonne, IL (United States); Northwestern Univ., Evanston, IL (United States)
Molten salts are promising reaction media candidates for the discovery of novel materials; however, they offer little control over oxidation state compared to aqueous solutions. Here, we demonstrated that when two hydroxides are mixed, their melts become fluxes with tunable solubility, which are surprisingly powerful solvents for ternary chalcogenides and offer effective paths for crystal growth to new compounds. We report that precise control of the oxidation state of Ni is achievable in mixed molten LiOH/KOH to grow single crystals of all known ternary K-Ni-S compounds. It is also possible to access several new phases, including a new polytope of β-K2Ni3S4, as well as low-valence KNi4S2 and K4Ni9S11. KNi4S2 is a two-dimensional low-valence nickel-rich sulfide, and β-K2Ni3S4 has a hexagonal lattice. Moreover, using KNi4S2 as a template, we obtained a new layered binary Ni2S by topotactic deintercalation of K. The new binary Ni2S has a van der Waals gap and can function as a new host layer for intercalation chemistry, as demonstrated by the intercalation of LiOH between its layers. The oxidation states of low-valence KNi4S2 and Ni2S were studied using X-ray absorption spectroscopy and X-ray photoelectron spectroscopy. Density functional theory calculations showed large antibonding interactions at the Fermi level for both KNi4S2 and Ni2S2 corresponding to the flat-bands with large Ni-d$$_{x^2}$$$$_{y^2}$$ character.
- Research Organization:
- Argonne National Laboratory (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division
- Grant/Contract Number:
- AC02-06CH11357
- OSTI ID:
- 1840545
- Journal Information:
- Journal of the American Chemical Society, Vol. 143, Issue 34; ISSN 0002-7863
- Publisher:
- American Chemical Society (ACS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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