Kelp derived hierarchically porous carbon aerogels with ultrahigh surface area for high-energy-density supercapacitor in aqueous electrolyte

Abstract

Nowadays, obtaining porous carbons from abundant and sustainable biomass as electrode materials for energy storage has been attracting tremendous attentions, to meet the requirement of energy consumption and environmental remediation. In this study, hierarchically porous carbon aerogels (HPCAs) with desirable micro-, meso- and macropores were obtained via decoloration, freeze-drying and subsequent carbonizing-activating process using kelp as sustainable, low-cost and massive precursors by adjusting the activation temperature. The effect of temperature on the pore structures and electrochemical performance of HPCAs were investigated in depth. At 800 °C, the as-obtained HPCA-800 had an appropriate combination of specific surface area and hierarchically porous networks, rendering the optimal capability of electrolyte ion's accumulation and transportation. The HPCA-800 exhibited highest specific capacitance of 278 F g−1 in 6 M KOH and 1965 F g−1 and 1 M KOH + 0.06 M K3Fe (CN)6 electrolyte, respectively, which are superior to those of the reported carbon aerogels. Moreover, an ultrahigh energy density of 93 W h kg−1 at high power density of 2109 W kg−1 was achieved in the redox electrolyte. The energy storage mechanism was also elucidated. The HPCAs from kelp should be promising and competitive electrode materials for constructing high-energy-density supercapacitor, owing to their outstanding supercapacitor performance together with the superior advantages of raw materials including abundance, low-cost and renewability.