Hierarchical porous hollow carbon microsphere/carbon nanotube heterostructures for high-performance supercapacitor

Constructing carbon nanotube (CNT)-based electrode materials is an effective strategy for the development of supercapacitors with high-rate capability. In this work, hierarchical porous hollow carbon microsphere (HCM)/CNT heterostructures were prepared by calcination of 3-aminophenol formaldehyde resin microspheres (AFSs) with the assistance of ethanolamine and Ni salts. This approach, which ingeniously combines the template and CVD methods, not only generates both HCMs and CNTs, but also achieves the growth of CNTs on HCMs. The length and dispersion of CNTs as well as the porous structure of HCMs could be easily controlled by adjusting the amount of ethanolamine and the size of AFS. Combining the advantages of the fascinating structure, i.e., abundant micro-, meso-, and macropores, high electrical conductivity, and good wettability induced by the presence of high-level N atoms, the optimal sample exhibited superior electrochemical performance, such as a high specific capacitance of 234.9 F g−1 at 2 A g−1, excellent cycling stability with the capacitance retention of 93.9 % after 10,000 cycles. More importantly, it possessed outstanding rate capability because its capacitance remained almost constant as the current density was increased above 5 A g−1. This research sheds light on an avenue to construct CNT-based carbon heterostructures for efficient energy storage.