First-principles investigation of the photocatalytic properties of two-dimensional CdO/ZrSSe heterojunctions

Two-dimensional van der Waals heterojunction materials have demonstrated significant potential for photocatalytic water splitting in hydrogen production, owing to their distinct electronic and optical properties. Among these materials, direct Z-scheme heterojunctions have attracted considerable attention in recent research. In this study, a novel CdO/ZrSSe heterojunction is designed using first-principles calculations. The structural stability, electronic properties, carrier mobility, optical absorption, and photocatalytic performance of this heterojunction are systematically investigated, with a particular focus on the influence of strain on the band structure. The results reveal that both type-I and type-II heterojunctions exhibit staggered, indirect bandgap structures, with bandgap values of 0.80 eV and 0.60 eV, respectively. A built-in electric field is established from the CdO layer to the ZrSSe layer, facilitating oxidation in the ZrSSe layer and reduction in the CdO layer. The highest carrier mobilities are calculated to be 462 cm² V⁻¹ s⁻¹ and 2738 cm² V⁻¹ s⁻¹, respectively. Under compressive strain, the bandgap widths of both I-CdO/ZrSSe and II-CdO/ZrSSe heterojunctions decrease, whereas tensile strain results in an increase in the bandgap width. Correspondingly, the optical absorption peaks of both heterojunctions are enhanced under compressive strain and diminished under tensile strain. These findings suggest that the performance of both type-I and type-II CdO/ZrSSe heterojunctions surpasses that of their individual monolayers, exhibiting a typical Z-scheme photocatalytic mechanism, and thus positioning them as promising high-efficiency catalysts for water splitting.