High-performance photocatalysts for overall water splitting: type-II WSi2N4/MoSi2N4 heterostructures

Abstract

We have conducted first-principles calculations to reveal type-II vdW heterostructures WSi₂N₄/MoSi₂N₄ with high catalytic performance, focusing on the excellent optoelectronic properties of the MA₂Z₄ family of 2D materials. Initially, we investigated the performance of photocatalytic water splitting of MA₂Z₄ family monolayers, which exhibit higher carrier mobility than traditional two-dimensional materials. Moreover, we built vdW heterostructures based on the MA₂Z₄ family to promote carrier spatial separation and suppress electron–hole interlayer recombination. The results show that the WSi₂N₄/MoSi₂N₄ heterostructure has negative binding energy (−33.47 meV Å⁻²) and forms a built-in electric field with an average charge transfer of 0.03e. Interestingly, we found that strain tuning can enhance the solar-to-hydrogen efficiencies to 18.01% at 3% biaxial strain, and the heterostructure exhibits a high light absorption coefficient with a band gap of 2.007 eV. In conclusion, the WSi₂N₄/MoSi₂N₄ heterostructure with high performance in photocatalytic hydrogen production represents a new impetus for achieving carbon neutrality.