Type-II 2D AgBr/SiH van der Waals heterostructures with tunable band edge positions and enhanced optical absorption coefficients for photocatalytic water splitting

Abstract

Utilizing two-dimensional (2D) heterostructures in photocatalysis can enhance optical ab-sorption and charge separation, thereby increasing solar energy conversion efficiency and tackling environmental issues. Density functional theory (DFT) was employed in this study to investigate the structural and optoelectronic properties of the AgBr/SiH van der Waals (vdW) heterostructures. All three configurations (A1, A2, and A3) were stable, with direct bandgaps of 1.83 eV, 0.99 eV, and 1.36 eV, respectively. The type-II band alignment in these structures enables electrons to be transferred from the SiH layer to the AgBr layer, and holes to move in the opposite direction. In the ultraviolet region, the optical absorption coefficients of the A1, A2, and A3 configurations are approximately 4.0 × 10⁵ cm⁻¹, significantly higher than that of an isolated AgBr monolayer (2.4 × 10⁴ cm⁻¹). In the visible light region, the A1 configuration has an absorption coefficient of 4 × 10⁴ cm⁻¹, higher than that of an isolated AgBr (2.2 × 10⁴ cm⁻¹). The band edges of the A1 configuration satisfy the redox potential for photocatalytic water splitting at pH 0–7. When the biaxial tensile strain is 5% for the A2 configuration and 2% for the A3 configuration, it can allow photocatalytic water splitting from half-reactions without strain to photocatalytic overall water splitting at pH 0–7. With a 5% biaxial tensile strain in the visible light region, the A1 and A3 configurations experience a rise in the maximum absorption coefficient of 5.7 × 10⁴ cm⁻¹ and 4.6 × 10⁴ cm⁻¹, respectively. The findings indicate that the AgBr/SiH vdW heterostructure configurations could be utilized in photocatalytic water-splitting processes with great potential.