Synthesis and Characterization of Discrete Nickel Phosphide Nanoparticles: Effect of Surface Ligation Chemistry on Catalytic Hydrodesulfurization of Thiophene

Discrete, unsupported nanoparticles of Ni2P have been prepared by using a solution‐phase method with bis(1,5‐cyclooctadiene)nickel(0) [Ni(COD)2] as the nickel source and trioctylphosphine (TOP) as the phosphorus source in the presence of the coordinating solvent trioctylphosphine oxide (TOPO). Ni2P nanoparticles prepared at 345 °C have an average crystallite size of 10.2 ± 0.7 nm and are capped with TOP and/or TOPO coordinating agents. The surface of the Ni2P nanoparticles can be modified by washing with CHCl3 or by exchanging TOP/TOPO groups with mercaptoundecanoic acid (MUA). The surface areas of these nanoparticles are on the order of 30–70 m2 g–1. As‐prepared and MUA‐capped nanoparticles undergo a phase transformation at 370 °C under reducing conditions, but CHCl3‐washed Ni2P nanoparticles retain the Ni2P structure. CHCl3‐washed and MUA‐capped nanoparticles exhibit higher HDS catalytic activity than as‐prepared nanoparticles or unsupported Ni2P prepared by temperature‐programmed reduction of a phosphate precursor. The surface modifications have a clear effect on the catalytic activity as well as the thermal stability of Ni2P nanoparticles under reducing conditions.