Layer-dependent photocatalysts of GaN/SiC-based multilayer van der Waals heterojunctions for hydrogen evolution

The development of non-precious, high-performance and environmentally friendly wide band gap semiconductor composite photocatalysts is highly desirable. Here, we report 2D GaN/SiC-based multilayer van der Waals heterostructures for hydrogen evolution and visible-light water splitting by using state-of-the-art hybrid density functional theory. We uncover that Bi-GaN/Bi-SiC owns two advantageous features for water decomposition: a type-II heterojunction and suitable band gap (2.05 eV). We demonstrate that the layer number plays a crucial role in the GaN/SiC-based composites. The type-II heterojunction is attributed to weak interlayer hybridization caused by multilayer SiC. Reduction of the band gap is attributed to lattice constant variation and interlayer interaction caused by the multilayer structure. Moreover, Bi-GaN/Bi-SiC shows the highest visible-light absorption coefficient on the whole, and exhibits an appropriate band gap that straddles the redox potential of water splitting at pH = 7. This work suggests that the band structure can be regulated by adjusting the number of GaN and SiC monolayers, providing theoretical guidance for experimental synthesis of GaN/SiC heterojunctions for hydrogen production.