N, S co-doped carbon spheres synthesized from glucose and thiourea as efficient CO2 adsorbents

Background: Synthesis of N, S co-doped carbon has been actively pursued due to their wide applications in different fields including CO2 adsorption. Methods: In the current work, spherical hydrochar was obtained from the hydrothermal carbonization of glucose. The hydrochar was then conveniently converted into N, S co-doped carbon sphere by KHCO3 activation in the presence of thiourea. Significant findings: The carbon spheres were successfully doped with high contents of nitrogen (4.8-13.0 wt%) and sulfur (2.4-5.6 wt%). The carbon spheres demonstrated specific surface area as high as 2581 m2/g. In-fluences of various physicochemical properties on CO2 uptake, adsorption heat, CO2/N-2 adsorption selectivity were studied and analyzed. CO2 uptake of 3.4 mmol/g at 25 degrees C and 1 bar was achieved by the carbon spheres. The results also showed that CO2 uptake was mainly decided by volume of small micropores. Nitrogen doping showed positive effects on improving CO2 uptake and adsorption selectivity, while sulfur doping significantly enhanced interaction strength and improved the adsorption heat. The current work demonstrated a convenient synthesis strategy of N, S co-doped carbonaceous CO2 adsorbents with controlled morphology. We hope this work will provide new insights into the synthesis and application of heteroatom doped carbons.