First-principles study of GeC/Ga2SO heterostructure as a potential direct Z-scheme photocatalyst for water splitting

The rational design of van der Waals heterostructure offers an effective avenue for improving the photocatalytic efficiency of individual two-dimensional materials, garnering extensive interest in recent years. Herein, the feasibility of GeC/Ga₂SO heterostructure as a photocatalyst for overall water splitting has been explored based on the first-principles calculations. Our findings reveal that the electronic bandstructure of GeC/Ga₂SO heterostructure can be engineered in staggered or straddling band alignment depending on stacking patterns. Particularly, in the GeC/Ga₂SO heterostructure with staggered band alignment, an intrinsic built-in electric field is established at the interface with the direction from GeC to Ga₂SO, facilitating the formation of a direct Z-scheme heterostructure. Also importantly, the band-edge positions of Z-scheme GeC/Ga₂SO heterostructure cross the water redox potentials, providing adequate driving force for both the reduction and oxidation reactions of water. Gibbs free energy calculations demonstrated that the photocatalytic overall water splitting can proceed spontaneously in the neutral environment (pH = 7) under light irradiation. Moreover, GeC/Ga₂SO heterostructure exhibits good thermal stability and a strong (magnitude in 10⁵ cm⁻¹) and broad (from visible to ultraviolet light) optical absorption. Finally, through applying the tensile strain, further enhancements in the optical absorption and carrier redox ability are achieved due to the favorable modulation in the bandgap. Therefore, all these features make GeC/Ga₂SO heterostructure show great potential in the application of photocatalytic water splitting.