Toward Realistic Z -Scheme Photocatalysts: Incorporating Surface–Adsorbate Interactions beyond Built-In Electric Field and Hot Carrier Dynamics

Existing approaches to model photocatalytic oxygen evolution reaction (OER) based on the built-in electric field E and nonadiabatic molecular dynamics provide useful insights into the charge transfer mechanism in 2-dimensional (2D) heterostructures. However, these approaches alone do not consider the reaction energetics on both sides of the heterostructure when deciding the reaction location. We apply the conventional approach to determine the type of charge transfer mechanism in the MoSi2P4/WTe2, MoSi2P4/GaN, and MoSi2P4/BAs heterostructures. The OER energetics on both sides of the heterostructures are then investigated to determine whether the sides predicted by the built-in E are indeed where OER favorably takes place. Our results show that based on the built-in E, MoSi2P4/WTe2 and MoSi2P4/GaN are Z-scheme heterostructures while MoSi2P4/BAs is a type-II heterostructure, with OER expected to occur at the MoSi2P4 surface. In contrast, the reaction energy diagram suggests that OER is more favorable on WTe2, GaN, and BAs for the respective heterostructures. Therefore, MoSi2P4/WTe2 and MoSi2P4/GaN are not ideal Z-scheme heterostructures and MoSi2P4/BAs is not an ideal type-II heterostructure. Interestingly, for the latter heterojunction, we identify an exceptionally high electron mobility of 105 cm2 V–1 s–1. This highlights the complexity of the phenomena and demonstrates that considering surface–adsorbate interactions on both sides of the heterostructure is crucial in designing ideal Z-scheme heterostructures.