Fabrication of nitrogen-doped hierarchical porous carbons from Sargassum as advanced electrode materials for supercapacitors

Using Sargassum as the precursor, a novel approach was developed to synthesize three-dimensional porous carbons as high-performance electrode materials for supercapacitors via KOH activation and subsequent nitrogen-doping employing melamine as the dopant. Melamine was decomposed in the presence of KOH under high-temperature conditions, leading to the formation of a unique spiderweb-like carbon structure. At a proper nitrogen doping amount, the as-synthesized N 0.67 @SAC showed a high specific surface area of 2928.78 m 2 g −1 with a large proportion of micropores, and its nitrogen content reached 1.07%. When used as the electrode material in a symmetric two-electrode system, N 0.67 @SAC exhibited a high gravimetric specific capacitance of 481 F g −1 at a current density of 1 A g −1 with a good rate capacity of 85% at 10 A g −1 . Nitrogen-doping can effectively improve the wettability of the material, and the pseudocapacitance is introduced by the Faraday reaction. N 0.67 @SAC also exhibited excellent cycling stability with a 100.7% retention rate after 10 000 cycles. Also, the N 0.67 @SAC showed a high specific energy of 16.68 W h kg −1 at a specific power of 628.9 W kg −1 at a current density of 1 A g −1 in the voltage range of 0–1 V.