Comparison of acid exfoliators in carbon nanosheets synthesis from stinging nettle (Urtica dioica) for electrochemical applications

Carbon nanosheets (CNs) were successfully synthesized from nettle stem (NS) which is an inexpensive material with a high carbon content that is abundantly available in nature. CNs were produced using chemical (potassium hydroxide activation and acid exfoliation) and thermal treatments. Sulfuric (H(2)SO(4)), phosphoric (H(3)PO(4)) and nitric (HNO(3)) acid solutions were used for exfoliation. CNs exfoliated by H(3)PO(4) have higher specific surface area (789 m(2) g(−1)) compared to CNs exfoliated by H(2)SO(4) (705 m(2) g(−1)) and HNO(3) (106 m(2) g(−1)). In this work, NSCNs were found to be a potential candidate for electrode material in electrochemical capacitors. The maximum specific capacitance of the NSCNs exfoliated by H(3)PO(4) is found to be 27.3 F g(−1) at a current density of 0.05 A g(−1), while the specific capacitance of NSCNs exfoliated by H(2)SO(4) and HNO(3) is 9.34 F g(−1) and 1.71 F g(−1), respectively. Energy density (0.06–0.95 Wh kg(−1)) and power density (20.9–26.7 W kg(−1)) of NSCNs are confirmed to be supercapacitor materials and can be applied in energy storage devices.