Electrochemical capacitance and hydrogen adsorption behavior of activated carbon derived from cattail fiber

Abstract In this paper, we have reported the synthesis of activated carbon (AC) from biomass cattail fiber through hydrothermal carbonization, followed by chemical activation, and its electrochemical capacitance and hydrogen storage properties. The AC exhibits a Brunauer‐Emmett‐Teller (BET) surface area ( S BET ) of 1597.5 m 2 g −1 , determined from the low‐pressure N 2 adsorption isotherm at 77 K using a BET‐multipoint plot. The AC sample shows a reversible hydrogen adsorption capacity of 0.25 wt.% H 2 (1.25 mmol H 2 g −1 ) at 293 K and 74 atm. The capacitance performance of AC was investigated with various conductive additives such as carbon nanotubes (CNTs), carbon black (CB), and reduced graphene‐oxide (rGO). From galvanostatic charge discharge (GCD) and cyclic voltammetry (CV) measurements, the as‐derived AC with polymer binder exhibits a specific capacitance ( C s ) of 245.2 F g −1 at 0.2 A g −1 and 158.1 F g −1 at 5 mV s −1 . Among the investigated conductive additives, AC with CNTs in KOH electrolyte exhibit highest C s of 326 F g −1 at 0.2 A g −1 and 173 F g −1 at 5 mV s −1 . Furthermore, the symmetrical two‐electrode device fabricated using AC with CNTs (as a conductive additive) in 1 M aq. Na 2 SO 4 electrolyte shows a C s of 97.2 F g −1 at 0.1 A g −1 . The energy and power densities of the two‐electrode device were observed to be 28 kW kg −1 and 2.64 Wh kg −1 , respectively.