H ₂ ‐Assisted Synthesis of Nickel Phosphide Nanocatalysts for the Hydrogenation of Phenylacetylene at Low Temperature

Abstract Nickel phosphide nanoparticles are used as catalysts in a wide range of chemical transformations such as hydrogenation. However, the synthesis of colloidal dispersion of these nanoparticles usually requires high reaction temperature and oleylamine as a reducing agent, which compromises the surface reactivity of the nanocatalysts. This work reports a robust new method of the synthesis of nickel phosphide nanoparticles assisted by H 2 and at a lower temperature of 200 °C. Well‐crystallized Ni 12 P 5 and Ni 2 P nanoparticles of 5.5 ± 0.5 nm were successfully prepared using tri‐ n ‐octylphosphine (TOP) as the phosphorus source. They were characterized by X‐ray diffraction and high‐resolution transmission electron microscopy. A higher temperature, reaction time, and TOP/Ni ratio favored the formation of a Ni 2 P phase over Ni 12 P 5 . These nanoparticles were used as catalysts for the hydrogenation of phenylacetylene. At high temperatures (80 and 100 °C), they allowed the full conversion of phenylacetylene to ethylbenzene. Interestingly, they were also active in the lower temperature regime, at 30 °C or even 0 °C, where significant conversions were obtained as soon as at least 0.1 equiv of tri‐ n ‐butylphopshine was added as a co‐catalyst, and styrene was the major product. The activity of this nanocatalyst in the low‐temperature regime outperformed that reported for other nickel phosphide nanoparticles with similar size, but prepared in the presence of oleylamine. This work highlights the relevance of H 2 ‐assisted synthesis for the production of nanocatalysts active at temperatures below 30 °C.