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 CO 2 adsorbents. The influences of porosity and heteroatom doping on CO 2 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 CO 2 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 m 2 /g and 0.50 cm 3 /g, respectively. Sulfur-doped carbons were also prepared without the addition of urea. Sulfur doping demonstrated positive effects on CO 2 adsorption at a low pressure. The sulfur-doped carbons showed adsorption properties similar to those of the co-doped carbons. The CO 2 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.