Structural and electronic properties of double-walled G-C3N4 nanotubes: a density functional theory study

In the present work, we investigated the geometric, electronic, and photocatalytic properties of g-C3N4single-walled nanotube (SWCNNTs) and g-C3N4double-walled nanotubes (DWCNNTs). The negative strain energy indicates that the SWCNNTs have a stable structure, while the most stable combination in the DWCNNT is (6, 0)@(12, 0). The energy band gaps of (n, 0) SWCNNTs increase while that of (n,n) SWCNNTs decrease as the diameter increase. Moreover, the calculated nanotubes have the ability of photocatalytic water splitting, and the valance band maximum of nanotubes are much lower than that of the monolayer, indicating that the nanotubes have better oxidation capacity than the monolayer. On the other hand, our calculations show that DWCNNTs have type II band alignment with a band gap width significantly smaller than that of SWCNNTs. Interestingly, DWCNNT exhibited a smaller effective mass of electrons than SWCNNTs, which is beneficial to electron migration. Therefore, the construction of nanotube is an effective way to improve the photocatalytic performance of g-C3N4monolayer materials.