Crystal-phase engineering of ZrS₂/γ-BC₆N heterostructures for enhanced type-II photocatalytic water splitting

The rational design of van der Waals heterostructures through crystal-phase engineering offers a promising yet underexplored avenue for developing high-efficiency photocatalysts. Moving beyond the conventional ZrS₂/h-BN system, this study introduces a dual-strategy of phase transition (from h-BN to γ-BN) and controlled carbon doping to dramatically enhance solar-driven water splitting. The calculations reveal that the optimized ZrS₂/γ-BC₆N heterostructure possesses an ideal indirect bandgap (2.30 eV) and a type-II band alignment, which synergistically promotes the spatial separation of photogenerated charge carriers. Its band edges fully span the water redox potentials from neutral to alkaline conditions, thermodynamically enabling overall water splitting. Remarkably, this crystal-phase-modulated heterostructure exhibits pronounced improvements in key functional properties: a visible-light absorption coefficient as high as 4.10 × 10⁵ cm^-1, a projected solar-to-hydrogen efficiency of 15.54%, and a power conversion efficiency of 10.50%, outperforming all comparable configurations in the series. These findings not only confirm the exceptional potential of the ZrS₂/γ-BC₆N heterostructure but also establish crystal-phase engineering combined with doping as a powerful and generalizable design paradigm for next-generation photocatalytic materials.