A multi-factor adjustable PtSe₂/GaN van der Waals heterostructure with enhanced photocatalytic performance

Two-dimensional van der Waals heterostructures with multiple tunable approaches in electronic and optical properties are highly superior for photocatalysis and novel devices. By applying first-principles calculations, we systematically studied the electronic structure, optical absorption, carrier mobility and solar-to-hydrogen efficiency of PtSe₂/GaN heterostructures, which are affected by different thicknesses, varying directions of polarization of the GaN nanosheets and applied mechanical strain of the whole system. The results indicate that these heterostructures exhibit thermodynamic stability at room-temperature (300 K), and most configurations have type-II band alignment, among which the heterostructure consisting of GaN trilayers and PtSe₂ shows high visible-light absorption (1.71 × 10⁵ cm^-1) and ultra-wide range of pH values (pH = 0-14) for the photocatalytic water splitting reaction and exceedingly high overpotential for the hydrogen evolution reaction (3.375 eV). Simultaneously, being two of the most significant parameters of photocatalysis and devices, the carrier mobility and solar-to-hydrogen efficiency have also been calculated, respectively, reaching up to 1601 cm² V^-1 s^-1 and 17.2%. Moreover, the photoelectrical properties can be highly tuned through further biaxial strain engineering; especially, the visible-light absorption can be enhanced to 2.85 × 10⁵ cm^-1 by applying 6% compression strain. Thus, the PtSe₂/GaN heterostructure we proposed shows a broad prospect for photocatalytic water splitting.