Stable cascade dual Z-scheme SnC/arsenene/HfS ₂ trilayer heterojunction for high-efficiency photocatalytic water splitting: a first-principles study

Efficient and stable photocatalysts are crucial for sustainable hydrogen production <i>via</i> solar water splitting. In this study, we design a cascade dual Z-scheme SnC/arsenene/HfS₂ trilayer heterojunction and systematically evaluate its photocatalytic performance using first-principles calculations. The heterostructure exhibits excellent thermodynamic and dynamic stability, supported by small lattice mismatch (<5%) and robust interlayer coupling. Built-in electric fields induced by interfacial charge redistribution facilitate directional carrier migration, enabling spatial charge separation through a cascade dual Z-scheme mechanism while retaining strong redox potentials. The band edge positions of SnC and HfS₂ satisfy the water redox requirements across various pH conditions. Notably, the hydrogen evolution reaction (HER) on the SnC layer proceeds spontaneously under illumination with a low energy barrier of 0.76 eV, driven by a 1.69 V photogenerated potential. Compared to their monolayer constituents, all three designed heterojunctions (cascade, arrow-up, and arrow-down) show significantly improved light absorption, with the cascade type exhibiting the broadest spectral response and achieving a high solar-to-hydrogen (STH) efficiency of 17.70%. These results demonstrate the promising potential of cascade-type dual Z-scheme trilayer heterojunctions as next-generation photocatalysts for solar-driven hydrogen production.