Facile synthesis of heteroatom-doped hierarchical porous carbon with small mesopores for high-performance supercapacitors

Structural optimization and doping engineering contribute to the promotion of insufficient specific capacitance and energy density for carbon-based supercapacitors. In this manuscript, heteroatom-doped hierarchical porous carbon with small mesopores (2-4 nm) is developed via a simple synthesis by carbonization and activation of an iron nitrate-induced self-assembled chitosan and sodium lignosulfonate composite aerogel. Chitosan and sodium lignosulfonate are utilized as carbon and heteroatom sources, while iron nitrate acts as the template and graphitization catalyst. With alkali activation, a heteroatom-doped hierarchical porous carbon with a high specific surface area, large proportion of small mesopores and well degree of graphitization was obtained, which is less reported in other articles. The optimal sample demonstrates a high specific capacitance (330 F g-1 at 0.5 A g-1), superior rate performance (270 F g-1 at 20 A g-1) and favorable cycling stability (95 % retention after 30,000 cycles). The corresponding symmetric supercapacitors are utilized in three different electrolytes and exhibit the maximum energy density of 40.76 Wh kg-1 at the power density of 450 W kg-1, as well as excellent rate performance and cycling stability. This study highlights the importance of small mesopores for the performance of carbon-based supercapacitors.