Computational Analysis of Pressure-Dependent Optimal Pore Size for CO2 Capture with Graphitic Surfaces

There are a growing number of reports suggesting that the specific surface area in graphitic materials is not a critical parameter to determine the CO2 capture capacity, but rather the pore size and its geometry are more relevant, yet a detailed theoretical and quantitative understanding that could facilitate further developments for the pore size effects is presently lacking. Using the thermodynamic continuum model combined with electronic structure calculations, we identify the critical size of pores in graphitic materials for enhanced carbon dioxide (CO2) uptake as well as its selectivity relative to N2. We find that there exists a value of pore size which is most optimal in the CO2 capture capacity as well as CO2/N2 selectivity at a given pressure and temperature, supporting the previous experimental observations regarding critical parameters determining the CO2 adsorption capacity of porous carbon materials. The calculated results emphasize the importance of graphitic pore size from 8 to10 Å in CO2 capture and selectivity against N2.