New Compounds and Phase Selection of Nickel Sulfides via Oxidation State Control in Molten Hydroxides

Xiuquan Zhou, David J. Mandia, Hyowon Park, Mahalingam Balasubramanian, Lei Yu, Jianguo Wen, Andrey Yakovenko, Duck Young Chung, Mercouri G. Kanatzidis*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


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 Ni2S, corresponding to the flat-bands with large Ni-dx2-y2 character.

Original languageEnglish (US)
Pages (from-to)13646-13654
Number of pages9
JournalJournal of the American Chemical Society
Issue number34
StatePublished - Sep 1 2021

ASJC Scopus subject areas

  • Chemistry(all)
  • Biochemistry
  • Catalysis
  • Colloid and Surface Chemistry


Dive into the research topics of 'New Compounds and Phase Selection of Nickel Sulfides via Oxidation State Control in Molten Hydroxides'. Together they form a unique fingerprint.

Cite this