DFT study on type-II photocatalyst for overall water splitting: g-GaN/C2N van der Waals heterostructure

Constructing van der Waals heterostructure has triggered enormous interest in the field of photocatalytic water splitting. Herein, we have investigated the structural, electronic and optical properties of g-GaN/C2N heterostructure by first-principles methods, and further discussed the implications from the viewpoint of photocatalytic applications. Our results show that g-GaN/C2N heterostructure is a type-II heterostructure, possessing staggered energy band arrangements, which benefits to the effective spatial-separation of photogenerated carriers. The bandgap is predicted to be 1.92 eV, governing a wide optical absorption spectrum from visible-light to ultraviolet-light with the magnitude of 105 cm−1. Moreover, its band edges span water redox potentials, satisfying the requirement of overall photocatalytic water splitting. In addition, the electronic properties of g-GaN/C2N heterostructure could be modulated by applying biaxal strain, resulting in an increasement of optical absorptions in the visible-light range. Finally, excellent stability of adsorbing water molecule on the g-GaN/C2N heterostructure is shown. These theoretical predictions suggest that the g-GaN/C2N heterostructure is promising for photocatalytic water splitting.