Binary nickel sulfides exist in a variety of phases and stoichometries, including NiS2, Ni3S4, α-NiS, β-NiS, Ni9S8, Ni7S6, and Ni3S2. Distinct phases of the binary nickel sulfide system have potential to be used as bifunctional electrocatalysts for water splitting, cathode materials for lithium-ion batteries, absorber layers for solar cells, hydrodesulfurization catalysts, or supercapacitors. However, the complicated nature of the Ni–S phase diagram makes the solution synthesis of phase-pure colloidal nanocrystals challenging. In this presentation, the phase-controlled solution synthesis of nickel sulfide nanocrystals is demonstrated. Nanocrystals of α-NiS, Ni9S8, and Ni3S2 can be independently prepared by tuning the key synthetic parameters of S:Ni precursor ratio, time, and temperature. The S:Ni precursor ratio in the synthesis influences the resulting nanocrystal phase, with sulfur-deficient Ni9S8 formed at low S:Ni and α-NiS at high S:Ni ratios. Low reaction temperatures favor Ni9S8 nanocrystals that then can be fully converted into α-NiS at higher temperatures along with longer reaction times. The more nickel-rich Ni3S2 phase is obtained by tuning the reactivity of the sulfur precursor – that is, a less reactive sulfur precursor at lower temperatures and shorter reaction times enable the formation of phase-pure Ni3S2 nanocrystals. This methodology allows a high level of control over nickel sulfide nanocrystal synthesis through a systematic investigation of the variable space that governs phase determination in the Ni–S system.

Synthetic phase control over colloidal nickel sulfide nanocrystals

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.