Evidence of the As/PtSe₂ Heterostructure with a Robust Built-In Electric Field as a Competitive Z-Scheme Photocatalyst for Overall Water Splitting

The Z-scheme heterostructure photocatalysts possess unique advantages compared with other heterostructures, primarily due to their capacity to effectively separate spatial carriers while maintaining strong redox capabilities. This study employs hybrid density functional theory calculations to examine the viability of As/PtSe₂ heterostructures as a catalyst for a Z-scheme photocatalytic system. The findings indicate that the As/PtSe₂ heterostructure exhibits type-II band alignments with a reduced band gap (E_g) relative to its individual monolayers, high carrier mobility in the order of 10³ to 10⁴ cm² V^-1 s^-1, and a robust built-in electric field of 0.38 V Å^-1, which improves visible light absorption and promotes the spatial separation of photogenerated carriers. Calculations also reveal that the As/PtSe₂ heterostructure possesses energetic, dynamical, and thermal stabilities. In terms of performance as a light absorber, both mesoscopic and microscopic approaches yield power conversion efficiencies greater than 11%. Furthermore, under small external potential bias, the hydrogen evolution reaction and oxygen evolution reaction can be initiated spontaneously on distinct monolayers, resulting in a calculated solar energy to hydrogen efficiency based on two distinctive models that exceeds the 10% critical value for economic viability.