Boosting the photocatalytic hydrogen evolution performance of monolayer C₂N coupled with MoSi₂N₄: density-functional theory calculations

Abstract

Very recently, an important two-dimensional material, MoSi₂N₄, was successfully synthesized. However, pure MoSi₂N₄ has some inherent shortcomings when used in photocatalytic water splitting to produce hydrogen, especially a low separation rate of photogenerated electron-hole pairs and a poor visible light response. Interestingly, we find that the MoSi₂N₄ can be used as a good modification material, and it can be coupled with C₂N to form an efficient heterojunction photocatalyst. Here, using density functional theory, a type-II heterojunction, C₂N/MoSi₂N₄, is designed and systematically studied. Based on AIMD simulations and phonon dispersion verification, C₂N/MoSi₂N₄ shows sufficient thermodynamic stability. As well as its perfect interface electronic properties, its large interlayer charge transfer and good visible light response lay the foundation for its excellent photocatalytic performance. In addition, the oxidation and reduction potentials of the C₂N/MoSi₂N₄ heterojunction not only can meet the requirements of water splitting well but can also maintain a delicate balance between oxidation and reduction reactions. More importantly, the |ΔG_H*| value of the C₂N/MoSi₂N₄ heterojunction is very close to zero, indicating great application potential in the field of photocatalytic water splitting. In brief, our research paves the way for the design of future MoSi₂N₄-based efficient heterojunction photocatalysts.