Calcium-Based Functionalization of Carbon Materials for CO2 Capture: A First-Principles Computational Study

We report a first-principles study of a CO2 gas-sorbent material consisting of calcium atoms and carbon-based nanostructures. In the low gas pressure regime, we find that Ca decoration of nanotubes and graphene possess unusually large CO2 uptake capacities (similar to 0.4-0.6 g CO2/g sorbent) as a result of their topology and a strong interaction between the metal dopants and CO2 molecules. Decomposition of the gas-loaded nanomaterials into CO gas and calcium oxide (CaO) is shown to be thermodynamically favorable; thus performance of the carbon capture process is further enhanced via formation of calcium carbonate (CaCO3). Gas adsorption CO2/N-2 selectivity issues have been also addressed with the finding that N-2 molecules bind to the metal-doped surfaces more weakly than CO2 molecules. The predicted molecular binding and accompanying gas selectivity features strongly suggest the potential of Ca-doped carbon materials for CO2 capture applications.