Investigating the Migration of Phosphorus in the Transformation of Branched Cobalt Nanoparticles to Cobalt Phosphide

The mechanism of formation of cobalt phosphide nanoparticles is investigated, wherein the migration of phosphorus atoms into the cobalt atomic lattice at high temperatures is examined utilizing high-resolution transmission electron microscopy and X-ray diffraction. Branched cobalt phosphide and dicobalt phosphide (CoP, Co2P) nanoparticles were synthesized under the seed-mediated method, using existing branched cobalt nanoclusters as the seed and trioctlyphosphine (TOP) as the source of phosphorus. The phosphorization was found to take place rapidly, with two concurrent reactions taking place─the conversion of Co to Co2P, and Co2P to CoP, in a kinetically controlled reaction determined by the quantity of binding phosphorus formed by the decomposition of TOP.