jp6b08641_si_001.pdf (215.13 kB)
Silicon-Doped Carbon Nanotubes: Promising CO2/N2 Selective Agents for Sequestering Carbon Dioxide
journal contribution
posted on 2016-10-10, 00:00 authored by Misaela Francisco-Marquez, Annia GalanoThe
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.