Fabrication of porous nitrogen-doped biochar from chitosan gel for high-performance supercapacitor via magnesium hydroxide templating and activating

To achieve the sustainable development and carbon neutral aim, renewable biomass chitosan was exploited to prepare active electrode materials for supercapacitor. Controllably structured Mg(OH) 2 was fabricated in situ during the chitosan gel formation, which functions as template and activator at the same time. The synthetic route was simplified only via one-step calcination at relatively low temperature. The accessed nitrogen-doped chitosan-derived biochar (NCB) features with hierarchical porous structure and large specific surface area. While applied as electrode material, the representative NCB exhibits the specific capacitance of 300 F g −1 at 1 A g −1 current density, which is 3.6 times of biochar prepared without Mg(OH) 2 templating. The cycling tests show that the specific capacitance is retained 93 % after running for 10,000 cycles, indicative of good long-term stability of NCB. Low cost, good stability, and high electrochemical performance make NCB a good candidate for the electrode material in supercapacitor. • One-step carbonization accesses N-doped chitosan-derived biochar for supercapacitor. • Magnesium hydroxide acts as activator and template at the same time. • Large specific surface area and hierarchical porous structure are achieved. • Specific capacitance of NCB-5 is 3.6 times that of biochar without adding template. • Good electrochemical performance and stability is retained even after 10,000 cycles.