Direct Z-scheme Hf2CO2/MoSSe van der Waals heterostructure for photocatalytic water splitting: high solar-to-hydrogen efficiency and excellent carrier mobility

Abstract

Photocatalytic water splitting for hydrogen production is crucial for the sustainable development of global energy resources. In this work, we employ first-principles calculations to construct a direct Z-scheme Hf₂CO₂/MoSSe heterostructure and systematically investigate its photocatalytic performance. The results indicate that the Hf₂CO₂/MoSSe heterostructure facilitates photocatalytic water splitting within a pH range of 0 to 10, demonstrating excellent pH tolerance, and exhibits a peak optical absorption of 2 × 10⁵ cm⁻¹ in the visible light range. The maximum solar-to-hydrogen (STH) efficiency reaches 22.52%, increasing to 34.48% with application of a +2% biaxial tensile strain. Applying an −8% biaxial compressive strain enhances the peak optical absorption within the visible light range by 30% compared to the intrinsic heterostructure. Furthermore, the carrier mobility of the heterostructure exhibits distinct anisotropy, with the electron and hole mobilities reaching 2767 cm² V⁻¹ s⁻¹ and 4287 cm² V⁻¹ s⁻¹, respectively, facilitating efficient spatial separation and rapid migration of photogenerated carriers. The calculation and screening to determine optimal adsorption sites for intermediate products reveal a Gibbs free energy change (ΔG) of 1.37 eV for the Hydrogen Evolution Reaction (HER), while the Oxygen Evolution Reaction (OER) proceeds spontaneously under illumination. These results all indicate that the Hf₂CO₂/MoSSe heterostructure is a highly promising candidate material for photocatalytically driven overall water splitting for hydrogen production.