Self-templated synthesis of microporous CoO nanoparticles with highly enhanced performance for both photocatalysis and lithium-ion batteries

Discrete and uniform microporous CoO nanoparticles with open nanochannels around 1 nm were one-pot synthesized by the self gas-leaching method via the thermal decomposition of a Co-oleylamine complex. CoO particle-sizes can be tuned from 50 to 13 nm by controlling the concentration of the cobalt precursor, accompanying a change of the long and winding nanochannels to short and straight nanochannels. It was shown that exposing the particle interiors to external active reactants via the shorter and straighter microporous nanochannels in smaller CoO nanoparticles can greatly enhance their photocatalytic efficiency. Most importantly, all the as-synthesized microporous CoO nanoparticles showed a very highly reversible capacity and cycling stability for lithium storage. The discharge and charge capacities of the microporous CoO sample with short straight nanochannels and the smallest particle size (1432.8 and 1200 mA h g, respectively) are up to two times higher than those of the commercial CoO powder (673.7 and 539 mA h g, respectively) and that of the theoretical value of CoO (715 mA h g) owing to the enlarged surface area, very small particle size for increased electrode and electrolyte contact and the heightened diffusion efficiency in short nanochannels for electrolyte and Li ions. The presence of microporous voids could effectively buffer the stress induced during lithium insertion-deinsertion alleviating the pulverization of electrode material, thereby giving extraordinary cycling stability.