Direct Z-scheme InN/InSe heterojunction with high solar-to-hydrogen efficiency for photocatalytic water splitting

• The InN/InSe heterojunction is a promising direct Z-scheme photocatalyst for overall water-splitting. • The InN/InSe heterojunction demonstrates enhanced visible-light absorption. • The InN/InSe heterojunction achieves a high solar-to-hydrogen energy conversion efficiency of 12.7 %. • Photoexcitation and interfacial electric field enable spontaneous HER and OER on the InN/InSe surface at pH = 10. Constructing rational two-dimensional van der Waals heterojunctions with efficient charge separation and strong redox capability is considered a promising strategy for developing high-performance photocatalysts. First-principles calculations are employed to assess the photocatalytic water-splitting capability of a novel two-dimensional InN/InSe heterojunction. The calculation results indicate that the InN/InSe heterojunction is characterized by a type-II staggered band alignment with a direct bandgap of 0.87 eV. The strong built-in electric field promotes the spatial separation of photogenerated carriers in the InN/InSe heterojunction, guiding charge transfer along a Z-scheme pathway, thereby achieving efficient carrier separation and robust redox capability. A pronounced enhancement in visible-light absorption is observed for the InN/InSe heterojunction compared to individual InN and InSe monolayers, which directly translates into an exceptional solar-to-hydrogen efficiency of 12.77 %. Furthermore, Gibbs free energy calculations confirm that overall photocatalytic water splitting reaction can proceed spontaneously on the InN/InSe heterojunction surface. These theoretical predictions suggest that the InN/InSe heterojunction is a promising candidate for solar-driven water-splitting applications.