Phosphorus-modulated controllably oxidized carbon nanotube architectures for the ultrahigh energy density of pseudocapacitive capacitors

Construction of heteroatoms modification of carbon nanotubes (CNT) is an attractive strategy to improve the stability and the energy density of advanced supercapacitors. Herein, the hierarchical phosphorus (P)-doped and ozonized CNT architectures (POCA) are prepared by the combination of simple ozonation, self-assembly and thermal activation approaches. The highly oxidative ozone gas would continuously etch unstable oxygen species and weaken the p-type effect of carbon nanotubes; while P atoms doping further modulates the electronic structure. As confirmed by spectroscopic and microscopic analysis, POCA exhibits a macroporous structure for fast ion diffusion and the formation of new functional groups (P-O, C-P) as the dominant active-sites for energy storage. The specific capacitance for POCA is reached up to 185.4 F g(-1) at 0.5 A g(-1) in a three-electrode configuration, which is superior to other control samples due to the additionally pseudocapacitive contribution. Furthermore, the symmetric POCA//POCA supercapacitor yields a high energy density of 19.2 Wh kg(-1) in 1 M Na2SO4 with a wide potential window of 1.8 V due to the synergistic effect of the hierarchical architecture and modulated surface chemistry. (C) 2020 Published by Elsevier Ltd.