Single-walled AlX (X=S, Se) Nanotubes for Photocatalytic Water Splitting: Analysis by Density Functional Theory

Here the geometry, electronic structure and photocatalytic properties of AlX (X = S, Se) nanotubes were calculated using the HSE06 functional. To analyze the stability of the nanotubes, we calculated the strain en-ergies, which decrease with increasing radius. The calculated band gap values for both AlS and AlSe nanotubes in the most stable structure are 2.27 eV and 2.04 eV, respectively, both of which are narrower than the band gap of the monolayer. Interestingly, Strain modulation also allows AlX nanotubes to meet the redox potential of spontaneous hydrolysis in different aqueous solutions of acid and neutral, where AlS nanotubes have-6.26 eV and-3.82 eV at the valence band maximum and conduction band minimum positions, respectively, at 5% tensile strain; while AlSe nanotubes have-6.18 eV and-3.99 eV at the band edge positions, respectively, satisfying the hydrolysis potentials at pH = 0 and 7. These unique and excellent properties also make AlX (X = S, Se) nanotubes promising as the next generation of one-dimensional photocatalysts.