Effects of Sulfur Doping and Humidity on CO₂ Capture by Graphite Split Pore: A Theoretical Study

By use of grand canonical Monte Carlo calculations, we study the effects of sulfur doping and humidity on the performance of graphite split pore as an adsorbent for CO₂ capture. It is demonstrated that S doping can greatly enhance pure CO₂ uptake by graphite split pore. For example, S-graphite split pore with 33.12% sulfur shows a 39.85% rise in pure CO₂ uptake (51.001 mmol/mol) compared with pristine graphite split pore at 300 K and 1 bar. More importantly, it is found that S-graphite split pore can still maintain much higher CO₂ uptake than that by pristine graphite split pore in the presence of water. Especially, uptake by 33.12% sulfur-doped S-graphite split pore is 51.963 mmol of CO₂/mol in the presence of water, which is 44.34% higher than that by pristine graphite split pore at 300 K and 1 bar. In addition, CO₂/N₂ selectivity of S-graphite split pore increases with increasing S content, resulting from stronger interactions between CO₂ and S-graphite split pore. Moreover, by use of density functional theory calculations, we demonstrate that S doping can enhance adsorption energy between CO₂ molecules and S-graphene surface at different humidities and furthermore enhance CO₂ uptake by S-graphite split pore. Our results indicate that S-graphite split pore is a promising adsorbent material for humid CO₂ capture.