A direct Z-scheme g-C6N6/InP van der Waals heterostructure: a promising photocatalyst for high-efficiency overall water splitting

An intrinsic out-of-plane electronic field can inhibit the recombination of photogenerated carriers in two-dimensional (2D) polar materials. On the other hand, a direct Z-scheme constructed from a 2D van der Waals heterostructure can not only effectively separate photogenerated carriers, but also can retain robust redox abilities. g-C6N6/InP, a direct Z-scheme heterostructure with a polarized material is successfully designed, which is verified to be available for overall water splitting through first-principles calculations. Due to the synergistic effects of intrinsic electric field and a direct Z-scheme heterostructure, hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) can simultaneously take place on the g-C6N6 and InP monolayer, respectively. The predicted solar-to-hydrogen efficiency can reach 21.69%, which breaks the conventional theoretical limit of similar to 18%. The suitable direction of intrinsic electronic field in the polar material can enhance the photogenerated carrier migration and redox abilities for both HER and OER. Based on these findings, the g-C6N6/InP vdW heterostructure can provide a new perspective for finding higher-efficiency Z-scheme photocatalysts with polar materials for overall water decomposition.