Effect of van der Waals stacking in CdS monolayer on enhancing the hydrogen production efficiency of SiH monolayer

Photocatalytic water splitting for the generation of hydrogen can be achieved by utilizing highly efficient type II van der Waals (vdW) heterostructures as a novel class of materials with a highly tunable bandgap energy and band alignment. Herein, we constructed a CdS/SiH vdW heterostructure by stacking CdS on the top of SiH monolayers and investigated its potential application as a photocatalyst for water splitting using first-principles calculations. The results indicated that a stable interface with vdW interactions can be formed between the CdS and SiH monolayers based on phonon dispersion and AIMD simulations. The CdS/SiH vdW heterostructure is an indirect bandgap semiconductor with a type II band alignment, allowing the effective separation of photoexcited electron-hole pairs. In addition, the very large electrostatic potential drop (14.59 eV) across the CdS and SiH interface is expected to hinder the recombination of electron-hole pairs, and hence promote efficient photocatalytic activity. Besides, compared with the isolated CdS and SiH monolayers, the CdS/SiH vdW heterostructure has a broad absorption edge in the high-energy visible light region. Furthermore, the bandgap energy and band alignment of this heterostructure could be modified by applying biaxial strain and an external electric field. Thus, our study showed that the CdS/SiH heterostructure with vdW interactions has excellent optical and electronic properties with great potential as a high-performance solar-driven photocatalyst for the water splitting reaction and nanoelectronic and optoelectronic devices. The bandgap energy and band alignment of the CdS/SiH vdW heterostructure were modified by applying biaxial strain and an external electric field.