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Binary alloys; Crystallinity; High resolution transmission electron microscopy; Hydrocarbons; Ionic liquids; Microwaves; Nanoparticles; Nickel; Scanning electron microscopy; Synthesis (chemical); X ray photoelectron spectroscopy, 1 ,5-cyclooctadiene; Energy dispersive X-ray spectrometry; High-angle annular dark fields; Microwave decomposition; Microwave-induced; Pentamethylcyclopentadienyl; Semihydrogenation; Wet chemical synthesis, Gallium alloys
Abstract:
NiGa is a catalyst for the semihydrogenation of alkynes. Here we show the influence of different dispersion times before microwave- induced decomposition of the precursors on the phase purity, as well as the influence of the time of microwave-induced decomposition on the crystallinity of the NiGa nanoparticles. Microwave-induced co-decomposition of all-hydrocarbon precursors [Ni(COD)2] (COD = 1,5-cyclooctadiene) and GaCp* (Cp* = pentamethylcyclopentadienyl) in the ionic liquid [BMIm][NTf2] selectively yields small intermetallic Ni/Ga nanocrystals of 5 ± 1 nm as derived from transmission electron microscopy (TEM) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and supported by energy-dispersive X-ray spectrometry (EDX), selected-area energy diffraction (SAED) and X-ray photoelectron spectroscopy (XPS). NiGa@[BMIm][NTf2] catalyze the semihydrogenation of 4-octyne to 4-octene with 100 selectivity towards (E)-4-octene over five runs, but with poor conversion values. IL-free, precipitated NiGa nanoparticles achieve conversion values of over 90 and selectivity of 100 towards alkene over three runs. © 2019 Simon et al.
