Polarization-direction-controlled Z-scheme photocatalytic switch in Sc2CO2/PtS2 heterostructures: A first-principles study

Constructing van der Waals (vdW) heterostructures is the most commonly used method for separating photogenerated carriers, which can effectively improve photocatalytic water-splitting efficiency. Although many vdW heterostructure photocatalysts have been proposed, there is still a lack of effective strategies to regulate the photocatalytic reaction ability. In this work, we propose a ${\mathrm{Sc}}_{2}{\mathrm{CO}}_{2}/{\mathrm{Pt}\mathrm{S}}_{2}$ heterostructure that can achieve the photocatalytic switch with different polarization directions (P \ensuremath{\uparrow} and P \ensuremath{\downarrow}). Both the P \ensuremath{\uparrow} and P \ensuremath{\downarrow} ${\mathrm{Sc}}_{2}{\mathrm{CO}}_{2}/{\mathrm{Pt}\mathrm{S}}_{2}$ heterostructures are semiconductors with type-II band-edge distribution. Remarkably, through the analysis of band arrangement and the built-in electric field, we found two completely different carrier-migration mechanisms inside the two heterostructures. The ${\mathrm{Sc}}_{2}{\mathrm{CO}}_{2}/{\mathrm{Pt}\mathrm{S}}_{2}$ heterostructure with P \ensuremath{\uparrow} can be used as a direct Z-scheme photocatalyst, showing great application prospect for water splitting. In contrast, the P \ensuremath{\downarrow} ${\mathrm{Sc}}_{2}{\mathrm{CO}}_{2}/{\mathrm{Pt}\mathrm{S}}_{2}$ heterostructure cannot undergo photocatalytic reactions affected by the direction of the built-in electric field. Therefore, based on ${\mathrm{Sc}}_{2}{\mathrm{CO}}_{2}/{\mathrm{Pt}\mathrm{S}}_{2}$ heterostructure, the ``on'' and ``off'' of photocatalysis are successfully achieved in a single material. Additionally, Gibbs free-energy calculation, high light absorption, and strain tunable band gap indicate that the ${\mathrm{Sc}}_{2}{\mathrm{CO}}_{2}/{\mathrm{Pt}\mathrm{S}}_{2}$ heterostructure is a promising candidate for photocatalytic applications.