Synthesis of shape-controllable cobalt nanoparticles and their shape-dependent performance in glycerol hydrogenolysis

Cobalt nanorods were synthesised in polyol using Ir as the nucleation agent and sodium stearate as the surfactant. The aspect ratios of the rods can be facilely mediated by the Ir/Co molar ratios. During rod growth, the solid cobalt alkoxide and stearate intermediates formed at the initial stages and acted as the reservoir to control Co reduction and then mediated the subsequent rod growth. Stearate played the critical role in controlling rod formation by its selective and covalent coating on the {10-10} planes, which induces anisotropic growth in the [0002] direction. The cobalt rods presented the hcp phase in the centre part and the fcc phase in the conical tips because of the difference in growth rate between stages, showing the hybrid crystallographic property. The slow growth can also induce the formation of fcc spheres by altering the amount of alkali in polyol. In glycerol hydrogenolysis, the hcp rods, which mainly expose the {10-10} planes, revealed much higher activity and 1,3-propanediol selectivity than the fcc spheres, demonstrating facet-dependent performance as a solid catalyst. To our knowledge, this is the first example of producing 1,3-propanediol using the facet effect of cobalt nanomaterials.