Salt Template Synthesis of Nitrogen and Sulfur Co-Doped Porous Carbons as CO2 Adsorbents

Because of their high stability, low cost, and tunable porosity, porous carbons are of great interest as CO2 adsorbents. The influences of porosity and heteroatom doping on CO2 adsorption depend on the specific adsorption conditions. In the current work, nitrogen and sulfur co-doped carbons were prepared with the assistance of an NaCl template, and the effects of different physicochemical parameters on CO2 adsorption at 20 bar were investigated. The co-doped carbons were synthesized with sodium lignosulfonate as the starting material and urea as the nitrogen source. The material showed a high specific surface area and pore volume of 973 m2/g and 0.50 cm3/g, respectively. Sulfur-doped carbons were also prepared without the addition of urea. Sulfur doping demonstrated positive effects on CO2 adsorption at a low pressure. The sulfur-doped carbons showed adsorption properties similar to those of the co-doped carbons. The CO2 uptake at 298 K and 20 bar was in the range of 4.3–7.5 mmol/g. The experiment results also revealed that the uptake at 20 bar correlated to the specific surface area of the carbon, while the doped heteroatoms only had secondary influences.