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

- Hierarchical-structured CoSe2@porous graphitic carbon/CNT nanocomposites are synthesized.
- Co nanoparticles play a key role in catalyzing the in-situ formation of graphitic carbon and extrusion of CNTs.
- Composite nanocubes exhibit excellent sodium storage performance and cyclic stability.

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.

We propose a two-step MOF-engaged approach for the fabrication of CoSe2 nanoparticles embedded within N-doped porous graphitic carbon nanocubes/CNT composite by the decomposition and further selenization of a Co-based zeolitic imidazolate framework precursor. Because of their unique features, the composites exhibit excellent sodium storage performance and cyclic stability.190