Preparation and electrochemical performance for supercapacitors of chitosan.based porous carbon materials

Nitrogen-containing mesoporous carbon with different specific surface areas and pore volumes were prepared by using colloidal silica spheres as the hard template, chitosan as a carbon precursor, and ZnCl2 as activation agent. The morphology, surface area, and pore structure of the prepared carbons were characterized by different techniques. The influence of the ratio of silica to chitosan and the use of ZnCl2 on the pore volume and surface area of porous carbon materials were explored. It was found that the nitrogen-doped mesoporous carbon (CSi-1.75) without using activation agent showed lowest surface area but the pore volume can reach up to 4.53 cm(3)center dot g(-1). The carbon (CSi-1.75-Zn) prepared by using ZnCl2 as activation agent, had the larger surface area (1 032 m(2)center dot g(-1)) and the pore volume decreased to 1.99 cm(3)center dot g(-1) and had more pyridine-nitrogen and pyrrole-nitrogen. In the three electrodes with 6.0 mol center dot L-1 KOH as the electrolyte, when the current density was 0.5 A center dot g(-1), the specific capacitance of CSi-1.75-Zn can reach 344 F center dot g(-1), while the specific capacitance of CSi-1.75 was only 255 F center dot g(-1). This indicates that the surface area of the carbon material had the greatest impact on the supercapacitive performance. The capacitance contribution analysis results showed that both the double-layer capacitance and pseudo capacitance of CSi-1.75-Zn were improved compared with CSi-1.75, indicating that larger specific surface area and more pyridine-nitrogen and pyrrole-nitrogen are conducive to improving the capacitance of carbon materials.