First principles study of structural and electronic properties of single and double-walled ZnSe nanotubes, toward the photocatalyst application

This study employed density functional theory (DFT) to investigate single-walled (SWZSNTs) and double-walled ZnSe nanotubes (DWZSNTs) for photocatalytic hydrogen production. Calculations revealed that SWZSNTs' bandgap decreased with diameter while showing negligible chirality dependence. HSE06 hybrid functional calculations yielded optimal bandgaps of 2.29 and 2.24 eV for (4,0)@(12,0) and (5,0)@(12,0) DWZSNTs, respectively, matching photocatalytic water splitting requirements. The DWZSNTs demonstrated efficient charge separation <i>via</i> a type-II band structure between the inner and outer tubes, with exceptional carrier mobilities (508.55 cm² V^-1 s^-1 for electrons and 46.27 cm² V^-1 s^-1 for holes) surpassing SWZSNTs and rivaling monolayer ZnSe. The visible-light-absorption spectra further confirmed DWZSNTs' superior performance compared to the single-walled structures, suggesting their strong potential as photocatalysts for hydrogen generation.