N-doped porous carbon from different nitrogen sources for high-performance supercapacitors and CO2 adsorption

Two types of carbon microspheres with abundant nitrogen-containing groups and porous structure were prepared via feasible and cost-effective methods, using chitosan (NCS-T) and glucose (NCS_NH3-T) as the raw materials, chitosan and ammonia as nitrogen source respectively. The effect of nitrogen sources on structure of N-doped porous carbon and their supercapacitors/CO₂ adsorption performance were discussed in details. The obtained carbon materials both exhibit a graphite-like structure with developed porous structures. For the NCS-T samples, N-5 and N-6 were the main nitrogen-containing groups, and OⅠ and OⅡ were the main oxygen-containing groups. For NCS_NH3-T samples, N exists as N-5, N-6 N-Q, and N-X groups, and O exists as OⅠ, OⅡ, and OⅢ groups. Micro-mesoporous structures developed, and on the specific surface area, pore volumes are more developed in NCS_NH3-T, mainly due to ammonia activation, which results in additional micropores especially ultramicropores (sizes<0.9 nm). The obtained carbon materials are well suited for use as an electrode material and adsorbent. In three-electrode system, the specific capacitances were in the range of 96–161 F/g for NCS-T, and the values reached 220–244 F/g for NCS_NH3-T at 0.2 A/g in 1 M H₂SO₄ electrolyte, it's the combination of electric double layer capacitors and faradaic pseudocapacitance. The CO₂ capture capacities were 51–141 mg/g for NCS-T and 180–243 mg/g for NCS_NH3-T, due to the developed micropores and ultramicropores. The results suggest that NCS_NH3-T can be a candidate as both electrode material and adsorbent.