We prepared carbon aerogel/RuO2 composites with three-dimensional microtubes based on renewable natural kapok fibers by combining a NaClO2 pretreatment, CO2 activation and loading of RuO2 nano-particles. The electrochemical performance of the material was optimized by tuning the carbonization temperature. The composite calcined at 800 degrees C for 2 h and activated by CO2 for 30 min possessed an integrated tubular structure and moderate pore size distribution. This composite material also showed highest specific capacitance of 433 F g(-1) at a current density of 1 A g(-1) with a capacitance retention of 91.5% for 2000 cycles in 3M KOH solution in three-electrode system. The maximum energy density was 8.92 Wh kg(-1) at 558.12 Wkg(-1) at a cell voltage of 1 V in 3.0M KOH aqueous electrolyte in a symmetric device. We attribute the reversible capacity of the obtained bio-derived carbon aerogel/RuO2 composites to the high-speed flow of the electrolyte in the unique hollow tubular structure, the appropriate pore size distribution and the synergetic effect of the high capacitance of RuO2 and good stability of the carbon material. (C) 2019 Elsevier Ltd. All rights reserved.