Cobalt nanowires prepared by heterogeneous nucleation in propanediol and their catalytic properties.

Co nanowires with a diameter of 10 nm and a length up to 1000 nm were synthesized by the chemical reduction of cobalt acetate in propanediol using Ru as the heterogeneous agent and stearic acid as the surfactant. The morphology of the Co nanomaterials depended strongly on the concentrations of stearic acid and sodium hydroxide and the temperature, which governed the reduction rate of Co(2+) in the liquid and the growth rate of Co nanocrystals. Very tiny Ru nanoparticles formed at the beginning of the synthesis significantly lowered the reduction temperature of Co(2+) species, affording an easy separation and growth of Co nanocrystals. Solid cobalt stearate and cobalt alkoxide were readily formed at the initial stage of the synthesis, which determined the reduction rate of Co(2+) through a dynamic equilibrium between the solid and the solution. In addition to forming cobalt stearate, the stearic acid, as a structure-directing agent, mainly induced the anisotropic growth of Co nanocrystals. The Co nanowires as heterogeneous catalysts showed quite promising activity and selectivity for the hydrogenation of citral and the hydrogenolysis of glycerol.