S-scheme MoSi2N4/AlN with a 2D heterojunction for photocatalytic water dissociation

Two-dimensional heterojunctions with higher carrier mobility and larger specific surface area exhibit numerous applications in photovoltaics and energy. In this work, the MoSi ₂N ₄/AlN heterojunction structure was established, and the first-principles calculations were performed on its electronic properties, photocatalytic properties and power conversion efficiency, oxygen and hydrogen evolution reaction, electronic and photovoltaic characteristics under electric fields and strains, along with the photogalvanic effect. The results reveal that the MoSi ₂N ₄/AlN heterojunction displays an indirect bandgap semiconductor with a bandgap of 1.91 eV, generating an intrinsic electric field at the interface from AlN to MoSi ₂N ₄. It conforms to the S-scheme carrier transfer mechanism and can completely cross the oxidation and reduction potentials of water at pH values of 0–14. The power conversion efficiency can reach up to 15.21 %. Hydrogen precipitation reaction occurs at the AlN side, while oxygen precipitation reaction generates at the MoSi ₂N ₄ side. At the photon energy of 2.5 eV, the maximum current can be achieved for the MoSi ₂N ₄/AlN heterojunction. This research can provide a novel strategy for the design and manufacture of optoelectronic devices with better performance.