Boosting photocatalytic hydrogen evolution through a Z-scheme BlueP/GaGeNO van der Waals heterostructure design

Creating efficient photocatalytic water-splitting materials with optimal band gaps in stacked two-dimensional structures is essential for sustainable hydrogen production and energy utilization. This study investigates the BlueP/GaGeNO van der Waals heterostructure (vdWH) using first-principles calculations to analyse its electronic, mechanical and photocatalytic properties, including optical behaviour, power conversion efficiency and water-splitting performance under strain. The outstanding stability of the heterojunction was verified using mechanical property evaluations, ab initio molecular dynamics simulations, and phonon dispersion analyses. The findings demonstrate that the BlueP/GaGeNO vdWH exhibits an indirect bandgap of 1.77 eV, with a built-in electric field at the interface directed from the GaGeNO layer toward the BlueP layer. The Z-scheme enhances the separation of charge carriers, enabling electrons and holes to participate more effectively in redox processes. The heterojunction demonstrates a power conversion efficiency of 36.9% and exhibits strong absorption in the visible spectrum, significantly improving its capacity to utilize solar energy efficiently. Strain engineering improves the BlueP/GaGeNO vdWH's electronic and optical properties by modifying the band structure, allowing an indirect-to-direct band gap transition under compressive biaxial strain. The absorption spectrum experiences a redshift under both tensile biaxial and compressive strain conditions. The Gibbs free energy analysis shows that the vdWH becomes catalytically active under illumination, where Z-scheme charge transfer stabilizes H* intermediates and enables spontaneous hydrogen evolution. Coupled with its robust stability and favourable band alignment, these results highlight the experimental feasibility and strong potential of BlueP/GaGeNO vdWH as a next-generation photocatalyst for efficient solar-to-hydrogen conversion and renewable energy applications.