Facile fabrication of hierarchical film composed of Co(OH)₂@Carbon nanotube core/sheath nanocables and its capacitive performance

Abstract

A hierarchical film composed of Co(OH)₂@carbon nanotube (CNT) core/sheath nanocables (CCNF) was generated <i>via</i> a simple and rapid electrophoretic deposition method. It is found that the Co(OH)₂ sheath was uniformly anchored on the surface of conductive CNT core. The Co(OH)₂ sheath, with a thickness of ∼20 nm, was composed of numerous very tiny nanoparticles. Such a unique nanostructure endows the CCNF with a high surface area of 126 m² g^-1 and a hierarchical porosity, resulting in a large accessible surface area for redox activity. As expected, the CCNF exhibits high specific capacitance and excellent rate performance. Its specific capacitance reached 1215 F g^-1 under a low current density of 1 A g^-1 and was maintained at 832 F g^-1 when the current density was increased 20 times to 20 A g^-1. A high capacitance retention of 99.3% was achieved after 10 000 cycles at 1 A g^-1. Such intriguing capacitive behavior is attributed to the synergistic effect of the CNT core and the Co(OH)₂ sheath.