Silicon-Doped Carbon Nanotubes: Promising CO2/N2 Selective Agents for Sequestering Carbon Dioxide

2016-10-10T00:00:00Z (GMT) by Misaela Francisco-Marquez Annia Galano
The potential ability of single-walled silicon–carbon nanotubes (SWSiCNTs) as CO2 scavengers was investigated using density functional theory calculations and (5,5) SWSiCNT models with 2%, 33%, and 50% Si. It was found that while the reactions between CO2 and pristine C tubes are endergonic, Si-doped materials have exergonic adsorption routes. It was also found that 50–50 Si–C composition is not required for the SWSiCNTs to be able to sequester CO2, which seems to be relevant because this is the maximum Si–C proportion allowed to maintain the SWSiCNT stability. The modeled SWSiCNTs are predicted to be selective to CO2 over N2, which is a critical feature for materials with potential applications for CO2 capture. The rate constants for the SWSiCNT reactions with CO2 were found to be around 105 M–1 s–1, which suggests that they are fast enough to ensure efficient CO2 capture at room temperature. In addition, for the SWSiCNT with 33% Si, the possibility of multiple CO2 adsorption was also investigated (up to seven CO2 molecules). It was found that all the consecutive reactions are significantly exergonic, which indicates that one SWSiCNT is able to sequester several CO2 equivalents. These findings suggest that SWSiCNT-based materials are promising candidates for selectively, and efficiently, sequestering CO2 molecules, in particular, SWSiCNTs with intermediate (2–33%) Si amounts.