Excellent sodium-ion storage performances of CoSe₂ nanoparticles embedded within N-doped porous graphitic carbon nanocube/carbon nanotube composite

A metal organic framework (MOF)-engaged approach is applied for the fabrication of CoSe₂ nanoparticles embedded within N-doped porous graphitic carbon nanocubes/carbon nanotubes (CoSe₂@N-PGC/CNTs). The composites are prepared by decomposition under the reducing atmosphere and further selenization of Co-based zeolitic imidazolate framework (ZIF-67) precursor. The metallic Co nanoparticles formed during the reduction process play a key role in catalyzing the in-situ formation of graphitic carbon and extrusion of CNTs from the surface of the composite nanocube using carbon sources originated from organic ligands in ZIF-67 templates. The direct selenization process of ZIF-67 produces the composite nanocubes (CoSe₂@AC) of CoSe₂ and amorphous carbon. The specific discharge capacities of the CoSe₂@NPGC/CNTs and CoSe₂@AC composite nanocubes after 100 cycles at a current density of 0.2 A g⁻¹ were 424 and 100 mA h g⁻¹, respectively. The excellent electrochemical performance of CoSe₂@N-PGC/CNTs composite nanocubes are attributed to their unique compositional and structural features. Especially, the carbon matrix with CNTs could not only effectively inhibit volume expansion during cycling but also maintain the integrity of the structure.