context: Similar to graphene, carbon nanotubes (CNTs) with a unique 1D tubular structure and excellent electrical conductivity can also be introduced into electrospun CNFs in order to increase the electrochemical activity of the electrospun CNFs and influence their architecture. Growing CNTs on the surface of the electrospun CNFs could be an effective approach to enhance the capacitive performance of electrode materials in SCs. For instance, a symmetrical device based on CNF/CNT hybrid electrodes exhibited a specific capacitance of 3.35 ± 0.05 mF cm−2, which was 3.6 times higher than that of a pure CNF electrode-based device (0.91 ± 0.02 mF cm−2). A hierarchical nanostructure of CNFs/CNTs was synthesized through a CVD process by using C2H2 as the carbon precursor and Ni nanoparticles on CNFs as catalysts.Fig. 12c shows an SEM image of the CNFs/CNTs nanocomposites, demonstrating the formation of a hierarchical network structure consisting of densely grown CNTs on the surface of the CNFs. The obtained CNFs/CNT electrode showed a specific capacitance of 464.2 F g−1 at 0.5 A g−1 in 6 M KOH and excellent stability with 97% retention after 10000 cycles. The excellent performance was ascribed to the following aspects: (i) the intimate contact between the CNTs (to provide electrical conduction from the tip of each CNT to the edges and surfaces of the CNFs) and the CNFs; (ii) the interconnected and porous CNFs acting as an excellent path facilitated charge transfer and electrolyte permeation. Hierarchical CNFs/CNT hybrids were prepared via a tubular CVD growth process using Al/Fe composite catalysts. After KOH activation, the tips of CNTs in the hybrids can be well opened at 700 °C without changing the overall hierarchical structure. More interestingly, the tip-open CNFs/CNT hybrids showed a considerably improved specific capacitance, which increases to 3.3 times that of the pristine one. Moreover, sweep analysis indicated that the diffusion-type capacitance increases by 3.7 times while the Helmholtz-type capacitance increases by only 1.5 times, indicating that the tip-open CNTs contribute to ∼30% of the increase in double-layer capacitance. In another study, CNFs/CNT scaffolds were fabricated by the electrospinning technique combined with post-carbonization processes. The diameters of CNF skeletons, CNT density on CNF skeletons and length of CNTs were determined by the PAN concentration, Fe(acac)3 concentration in precursor solution and growth time of C2H2 flow, respectively. It was observed that a suitable size of CNF skeletons, CNT density and growth time of CNTs could greatly enhance the overall performance.