Gelatin-derived nitrogen-doped porous carbon via a dual-template carbonization method for high performance supercapacitors
High performance nitrogen-doped porous carbon for supercapacitors, named as Gelatin–Mg–Zn-1 : 5 : 3, has been successfully prepared via a dual-template carbonization method, without any physical/chemical activation process, in which gelatin serves as both carbon/nitrogen source, and low cost Mg(NO3)2·6H2O and Zn(NO3)2·6H2O as dual templates. It is revealed that the carbonization temperature, and the mass ratio of gelatin–Mg(NO3)2·6H2O–Zn(NO3)2·6H2O plays a crucial role in the determination of surface area, pore structure and the correlative capacitive behavior of the Gelatin–Mg–Zn-1 : 5 : 3 sample. It displays a high BET surface area of 1518 m2 g−1, large total pore volume of 4.27 cm3 g−1, and large average pore width of 11.3 nm. In a three electrode system, using 6 mol L−1 KOH solution as electrolyte, we can achieve a high specific capacitance of ca. 284.1 F g−1 at a current density of 1 A g−1 and high capacitance retention of ca. 31.2% is obtained at 150 A g−1, indicating high rate capability. It also possesses a high capacitance retention of ca. 96.1% even after charging/discharging for 10 000 cycles. More importantly, a two electrode system, using [EMIm]BF4/AN (weight ratio of 1 : 1) as electrolyte, has been adopted for the Gelatin–Mg–Zn-1 : 5 : 3 sample with different operation temperatures of 25/50/80 °C. As a result, wide voltage windows, broad operation temperatures, and high cycling stability achieved in the two electrode system make it possible for practical application under extreme conditions.