No abstract

No abstract

Spherical nitrogen-doped porous carbons have been prepared through a template carbonization method, in which polyacrylamide (PAM) serves as carbon and nitrogen sources, and calcium acetate as hard template. It reveals that the mass ratio of polyacrylamide and calcium acetate and the carbonization temperature have crucial impacts upon the pore structures and the correlative capacitive performance. The PAM-Ca-650-1:3 sample displays the best capacitance performance. It is amorphous with low-graphitization degree, possessing a total BET surface area of 648 m2 g–1 and total pore volume of 0.59 cm3 g–1. At a current density of 0.5 A g–1, the resultant specific capacitance is 194.7 F g–1. It exhibits high capacitance retention of 97.8% after charging–discharging 5000 times. The polyacrylamide used is cheap and commercially available, making it promising for large-scale production of porous carbons containing nitrogen as an excellent electrode material for supercapacitor.

No abstract

In this work, nitrogen-doped sheetlike carbon materials have been synthesized by a template carbonization method using 1,5-diphenylcarbazide and MgCl2·6H2O as carbon source and template, respectively. The method presents a carbon sample with amorphous characteristics as well as high surface area and large pore volume. More importantly, introducing the redox additives 4-hydroxybenzoic acid (HBA), 3,4-dihydroxybenzoic acid (DHBA), and 3,4,5-trihydroxybenzoic acid (THBA) with functional hydroxyl groups into 1 mol L–1 H2SO4 has largely improved the capacitances as well as the energy density. As expected, the supercapacitor with the redox additive HBA exhibits higher capacitances, with an increase of 1.57 times compared with the conventional H2SO4 electrolyte. Besides, compared with the supercapacitor without any redox additive, the redox additive DHBA produces a large improvement of capacitances, increasing by 3.18 times. In addition, the redox reactions of HBA and DHBA are reversible, while that of THBA is irreversible. Moreover, HBA with a hydroxyl group can release/gain a proton/electron, and DHBA, which owns a pair of hydroxyl groups, can release two protons/electrons. Moreover, both of the redox processes of HBA and DHBA are controlled by a diffusion mechanism.