The Influence of Particle Size and Shape in Cobalt 2-Methylimidazolate Polymers on Catalytic Properties

Abstract

The reaction products between in situ generated Co(OH)2 and 2-methylimidazole were studied and characterized. Using 9 fold excess of ligand, the well studied polyhedral (dodecahedral) particles (1–3 μm diameter) of the zeolitic imidazolate framework were obtained, i. e. ZIF-67. When a stoichiometric amount of 2-methylimidazole was employed, amorphous spheres of ca 500 nm diameter were obtained with low dispersion in size. Both samples were pyrolyzed at 700 and 900 °C under inert atmosphere. The external morphology was kept, however TEM images of the spherical particles showed that they were mainly composed of carbon nanotubes. Co nanoparticles embedded in the carbonaceous matrix could be observed in both samples. The activity of the pyrolyzed (700 and 900 °C) acid leached samples towards the Oxygen Reduction Reaction was studied. Upon the same thermal treatment both types of samples showed similar electrokinetic parameters.