Highly mesoporous carbon nanofiber electrodes with ultrahigh specific surface area for efficient capacitive deionization

Porous carbon with high specific surface area (SSA) has attracted considerable attention in capacitive deionization (CDI) owing to the abundant active adsorption sites. However, porous carbon dominated by the micropores tends to increase the ion transfer resistance and overlap the electrical double layers (EDLs), greatly limiting the ion adsorption rate and amount. In this work, a highly mesoporous carbon nanofiber electrode with an ultrahigh specific surface area (SSA) was prepared via electrospinning ZIF-8/benzoxazine/polyacrylonitrile (ZIF-8/BA-a/PAN) composite solution as carbon precursor. Benefiting from the cooperation of the simultaneous evaporation of Zn in ZIF-8 and activation treatment, the resultant carbon nanofibers show an ultrahigh SSA of 3066.29 m2/g, a pore volume of 2.23 cm3/g and a mesopore ratio of 72.53%, which has a high salt adsorption capacity (SAC) of 47.22 and 63.83 mg/g in 500 mg/L NaCl (50 mL) solution at 1.2 and 1.6 V, respectively. Furthermore, electrochemical measurement revealed that the high electrical double-layer capacitance facilitates ion storage in the mesoporous carbon nanofibers due to the increased nanopore size and reduced EDLs overlapping. This work provides new insight into designing novel highly mesoporous carbon with ultrahigh SSA for the next-generation electrode materials for energy and environmental applications.