Theoretical prediction of two-dimensional ZnO/GaN van der Waals heterostructure as a photocatalyst for water splitting

In this work, based on density functional calculations, the structural, electronic, interfacial and optical performances of the two-dimensional van der Waals (vdW) heterostructure formed by ZnO and GaN are addressed. The heterostructure possesses a type-II band structure and decent band edge positions which can separate the photogenerated electron-holes pairs constantly for redox reaction of the water splitting at pH 0 and 7. The charge-density difference and potential drop across the interface of the heterostructure are investigated, which can result a built-in electric field to prevent the recombination of the photogenerated electron-holes. Besides, the high mobility of electrons about 3004.49 cm(2).V-1.s(-1) is found in the heterostructure along the transport direction. The heterostructure also has excellent optical absorption performance, which can be mediated by the external strain. This study offers guidelines for the design of vdW heterostructures used as photocatalysts for water splitting.