Effects of Surface Heterogeneity on the Adsorption of CO₂ in Microporous Carbons

Abstract

Carbon capture combined with utilization and storage has the potential to serve as a near-term option for CO₂ emissions reduction. CO₂ capture by carbon-based sorbents and CO₂ storage in geologic formations such as coal and shale both require a thorough understanding of the CO₂ adsorption properties in microporous carbon-based materials. Complex pore structures for natural organic materials, such as coal and gas shale, in addition to general carbon-based porous materials are modeled as a collection of independent, noninterconnected, functionalized graphitic slit pores with surface heterogeneities. Electronic structure calculations coupled with van der Waals-inclusive corrections have been performed to investigate the electronic properties of functionalized graphitic surfaces. With Bader charge analysis, electronic structure calculations can provide the initial framework comprising both the geometry and corresponding charge information required to carry out statistical modeling. Grand canonical Monte Carlo simulations were carried out to determine the adsorption isotherms for a given adsorbent–adsorbate interaction at temperature/pressure conditions relevant to carbon capture applications to focus on the effect of the surface functionalities. On the basis of the current work, oxygen-containing functional groups were predicted to enhance CO₂ adsorption in microporous carbon materials in the absence of water vapor, and the hydrated graphite was found to hinder CO₂ adsorption