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

• N, S co-doped carbon spheres are prepared from glucose derived hydrochar. • Thiourea is used as the nitrogen and sulfur sources simultaneously. • Nitrogen and sulfur contents are 4.8–13.0 wt% and 2.4–5.6 wt%, respectively. • The carbon spheres show high surface area of 2581 m 2 /g. • The maximum CO 2 uptake achieved at 25 °C and 1 bar is 3.4 mmol/g. Synthesis of N, S co-doped carbon has been actively pursued due to their wide applications in different fields including CO 2 adsorption. 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 KHCO 3 activation in the presence of thiourea. 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 m 2 /g. Influences of various physicochemical properties on CO 2 uptake, adsorption heat, CO 2 /N 2 adsorption selectivity were studied and analyzed. CO 2 uptake of 3.4 mmol/g at 25 °C and 1 bar was achieved by the carbon spheres. The results also showed that CO 2 uptake was mainly decided by volume of small micropores. Nitrogen doping showed positive effects on improving CO 2 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 CO 2 adsorbents with controlled morphology. We hope this work will provide new insights into the synthesis and application of heteroatom doped carbons.