DFT Studies on the Effects of C Vacancy on the CO2 Capture Mechanism of Silicon Carbide Nanotubes Photocatalyst (Si12C12-X; X = 1; 2)

In this work, we have investigated the capability of CO 2 capture by single-walled, carbon-deficient silicon carbide nanotubes (Si 12 C 12 -X; X = 1; 2). All calculations of the properties of the investigated systems were performed using density functional theory with plane wave basis sets and pseudopotentials. Electronic interactions were determined using the generalized gradient approximation method in terms of the Perdew-Burke-and Ernzerhof exchange–correlation functional. The analysis of the photoabsorption properties of the investigated systems was based on structural, electronic and optical properties. Analysis of the structural properties revealed that as number of C vacancy increases, bond length decreases, which agrees well with previous literature. Regarding the CO 2 overpotential value, both Si 12 C 11 :V c1 and Si 12 C 10 :V c2 showed band edges of -1.5 eV and -1.45 eV, respectively, which are more negative than the standard overpotential value (-1.4 eV) for CO 2 reduction. Analysis of the optical absorption spectra revealed good photon absorption by Si 12 C 11 :V c1 (4.16% defect) and Si 12 C 10 :V c2 (8.33% defect) in the visible region accompanied by negligible electron–hole recombination, while pristine SWSiCNT showed absorption in the UV region accompanied by strong electron–hole recombination. This study found that Si 12 C 11 :V c1 and Si 12 C 10 :V c2 are well-suited for CO 2 capture and storage, while underlining the CO 2 capture capability of pristine SWSiCNT.