First-principles calculations of a direct Z-scheme AsP/SnSe2 heterojunction with high solar-to-hydrogen efficiency

Abstract

Seeking efficient photocatalysts for hydrogen production is one of the effective strategies to mitigate global energy scarcities and environmental degradation. This study investigates the electronic properties, optical properties, and photocatalytic efficiency of the AsP/SnSe₂ van der Waals heterojunction (vdwH) based on first-principles density functional theory (DFT). The results show that the AsP/SnSe₂ vdwH has an indirect bandgap of 0.62 eV and a Type II band structure. Charge density difference calculations reveal the formation of an internal electric field oriented from AsP to SnSe₂ at the heterointerface. Under light excitation, the photogenerated carrier transfer mechanism within the AsP/SnSe₂ heterojunction follows a Z-scheme mechanism, retaining strong redox reaction activity. Additionally, the AsP/SnSe₂ heterostructure exhibits superior visible light absorption performance compared to the two single-layer structures, reaching a maximum of 4.44 × 10⁵ cm⁻¹ in the visible light range. The solar-to-hydrogen efficiency (${\eta }_{\text{STH}}$) of the heterojunction is 20.93 %. Surprisingly, when the compressive strain reaches −4 %, the band edge position of the heterojunction can meet the photocatalytic water splitting potential requirements under full pH conditions, and the ${\eta }_{\text{STH}}$ reaches as high as 38.55 %, demonstrating that utilizing strain engineering to modulate the photocatalytic performance of heterojunctions constitutes a viable approach. The AsP/SnSe₂ heterojunction holds promise as a strong contender for next generation photocatalysts.