Phase-controlled solvothermal syntheses and oxygen evolution reaction (OER) activity of nickel sulfide nanoparticles obtained from 1,2-bis(diphenylphosphino)ethane nickel(ii) acetylacetonatedithiolate

A new heteroleptic nickel(ii) complex, [Ni(dppe)(acac)]·CHCl₃ (1) (where acac = acetylacetonatedithiolate, dppe = 1,2-bis(diphenylphosphino)ethane), has been synthesized and characterized using different spectroscopic techniques and single-crystal X-ray diffraction. The solvothermal decomposition of the complex in two different solvents, viz. 1-dodecanethiol (DT) and octadecyl amine (ODA), yielded two different nickel sulfides, viz.Ni-DT and Ni-ODA, respectively. These sulfides have been characterized by PXRD and SEM. Rietveld refinement analyses of Ni-DT revealed that it comprises two phases of nickel sulfide, viz. NiS and Ni₃S₃, while Ni-ODA possesses only a single phase of Ni₂S₃. The newly synthesized materials have been used as electrocatalysts for the oxygen evolution half-cell reaction of water splitting. The electrochemical studies suggest that Ni-DT/Ni-ODA has a good electrocatalytic activity towards the OER at a low overpotential of ∼200 mV with η¹ being 342 mV and 243 mV for Ni-DT and Ni-ODA, respectively, at a scan rate of 1 mV s⁻¹