Enhancing solar-to-hydrogen efficiency with an S-scheme GaTe/PtS2 van der Waals heterojunction with high light absorption†

To tackle the urgent challenges posed by the current energy crisis and environmental concerns, the potential of photocatalytic water splitting has been recognized as a promising solution. In this study, we investigate the structural, electronic, and optical properties of a van der Waals heterojunction (vdwH) formed by combining GaTe and PtS₂ using first-principles calculations. We also examine the Bader charge and solar hydrogen efficiency of this heterojunction to gain insights into its potential for practical applications. The GaTe/PtS₂ heterojunction as a step-scheme (S-scheme) heterojunction has a similar structure to the traditional type-II heterojunction, that is, photo-generated carriers can be automatically separated in space. Analysis of the average charge density difference reveals the presence of a built-in electric field within the heterojunction, which effectively extends the lifetime of carriers. When pH = 0, GaTe/PtS₂ can promote a redox reaction to split water. The high photocatalytic activity of GaTe/PtS₂ is evidenced by its strong light absorption coefficient in the absorption spectrum. Effective modification of the band edge position and optical properties can be achieved through biaxial strain, resulting in increased participation of photons in water splitting. Additionally, the GaTe/PtS₂ heterojunction boasts an impressive solar-to-hydrogen efficiency of 45.88%, and when ε = 4%, the η_STH reaches 52.18%. Thus, our study demonstrates that the GaTe/PtS₂ heterojunction is a promising S-scheme photocatalyst for comprehensive water splitting.