Nickel Phosphide Nanoparticles for Selective Hydrogenation of SO₂to H₂S

Highly mesoporous SiO₂-encapsulated NixPycrystals, where (x,y) = (5, 4), (2, 1), and (12, 5), were successfully synthesized by adopting a thermolytic method using oleylamine (OAm), trioctylphosphine (TOP), and trioctylphosphine oxide (TOPO). The Ni₅P₄@SiO₂system shows the highest reported activity for the selective hydrogenation of SO₂toward H₂S at 320 °C (96% conversion of SO₂and 99% selectivity to H₂S), which was superior to the activity of the commercial CoMoS@Al₂O₃catalyst (64% conversion of SO₂and 71% selectivity to H₂S at 320 °C). The morphology of the Ni₅P₄crystal was finely tuned via adjustment of the synthesis parameters receiving a wide spectrum of morphologies (hollow, macroporous-network, and SiO₂-confined ultrafine clusters). Intrinsic characteristics of the materials were studied by X-ray diffraction, high-resolution transmission electron microscopy/scanning transmission electron microscopy-high-angle annular dark-field imaging, energy-dispersive X-ray spectroscopy, the Brunauer-Emmett-Teller method, H₂temperature-programmed reduction, X-ray photoelectron spectroscopy, and experimental and calculated³¹P magic-angle spinning solid-state nuclear magnetic resonance toward establishing the structure-performance correlation for the reaction of interest. Characterization of the catalysts after the SO₂hydrogenation reaction proved the preservation of the morphology, crystallinity, and Ni/P ratio for all the catalysts.