Direct Z-scheme photocatalytic overall water splitting on 2D CdS/InSe heterostructures

Using first-principles calculations, we investigated the photocatalytic mechanism of two-dimensional van der Waals CdS/InSe heterostructures (HSs). Our results show that the buckling distortion of a CdS monolayer sheet in the CdS/InSe HSs induces a built-in polarized electric field, which significantly changes the band edge positions of the InSe layer. The band alignment indicated that the photogenerated electrons in the conduction band (CB) of the InSe monolayer have a high possibility of recombining with the holes in the valence band (VB) of the CdS sheet, resulting in the electrons in the CB of CdS participating in a reduction reaction and the holes in the VB of InSe taking part in an oxidation reaction. This direct Z-scheme photocatalytic system can lead to spatial separation of photogenerated carriers and excellent redox ability, thus enhancing the photocatalytic efficiency. Meanwhile, CdS/InSe HSs can significantly extend the range of light harvesting from visible light to infrared light. Similar results can also be found in the CdS/InSe@2 HSs constructed by InSe bilayer deposit on a CdS nanosheet. These results indicate that CdS/InSe HSs are promising photocatalysts for water splitting.