Fabrication of three-dimensional microtubular kapok fiber carbon aerogel/RuO2 composites for supercapacitors

We prepared carbon aerogel/RuO 2 composites with three-dimensional microtubes based on renewable natural kapok fibers by combining a NaClO 2 pretreatment, CO 2 activation and loading of RuO 2 nanoparticles . The electrochemical performance of the material was optimized by tuning the carbonization temperature. The composite calcined at 800 °C for 2 h and activated by CO 2 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 3 M KOH solution in three-electrode system. The maximum energy density was 8.92 Wh kg −1  at 558.12 W kg −1  at a cell voltage of 1 V in 3.0 M KOH aqueous electrolyte in a symmetric device. We attribute the reversible capacity of the obtained bio-derived carbon aerogel/RuO 2 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 RuO 2 and good stability of the carbon material.