Almond Shell‐Derived Carbons under Low‐Temperature Activation with Ultra‐High Surface Area and Superior Performance for Supercapacitors

Abstract Nitrogen containing almond shell‐derived porous carbons (ACs) have been synthesized by adding sodium amide (NaNH 2 ) as activator in calcination process. The optimized carbon material is denoted as AC‐4‐550 (mass ratio of NaNH 2 /C equals 4 and activation temperature is 550 °C). AC‐4‐550 possesses a high specific surface area of 3249.68 m 2 g −1 and total pore volume of 1.85 cm 3 g −1 with approximately a half proportion of micropores. Theoretically, the heteroatoms generate pseudocapacitance and wettability, the high specific surface area provides more active adsorption sites for ions, the micropores reduce the thickness of electrical double layer to enhance capacitance and the mesopores speed up the ion transmission. In a three‐electrode supercapacitor in 6 M KOH aqueous electrolyte, the specific capacitance reached to 440.29 F g −1 at 1 A g −1 , even 240.00 F g −1 at 50 A g −1 . And after 10 000 cycles, AC‐4‐550 retains 92% capacitance at 10 A g −1 . Furthermore, the high energy density (129.40 W h kg −1 at a power density of 900 W Kg −1 ) in a symmetrical coin‐cell capacitor using ionic liquid electrolyte demonstrates the possible applications in practical situation.