Effect of nitrogen doping on physical and electrochemical properties of resorcinol / formaldehyde based carbons

Nitrogen doped resorcinol (R) and formaldehyde (F) based polymeric gels were synthesised by polymerisation reaction. Nitrogen heteroatoms were incorporated in the bulk network of polymeric gels using melamine as nitrogen source. The resultant aerogels were carbonized at a temperature range 750 to 900 ºC under Ar to prepare nitrogen doped carbon aerogels used as the electroactive material for the fabrication of electrodes for electrochemical capacitor. The porous structure of carbon aerogels was characterised by nitrogen adsorption- desorption. Contact angle measurements were performed to investigate the wettability of the electrodes toward the electrolyte when used in the electrochemical cell. The electrochemical properties of the carbon aerogels were characterized by, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements. The experimental results revealed that resorcinol / catalyst (R/C) and resorcinol / melamine (R/M) ratios played crucial role in the development of porous structure (specific surface area, average pore size and pore size distribution) of the resultant carbons.
Nitrogen content played an important role to improve wetting behaviour and capacitive performance of the electroactive material. The carbon material MRFC-100-800-R/M80 with an R/C ratio of 100 and an R/M ratio of 80 carbonized at 800 ºC exhibited much improved wettability with 6 M KOH showing considerable decrease in the contact angle from 125º to 103º. Improved capacitance of 208 Fg^-1 was achieved for N-doped carbon sample MRFC-100-800-R/M80 as compare to the specific capacitance of 136 Fg^-1 for an un-doped carbon prepared under similar conditions.