Internal electric field enhanced photoelectrochemical water splitting in direct Z-scheme GeC/HfS2 heterostructure: A first-principles study

Designing direct Z-scheme heterostructure photocatalysts has received enormous attention due to the efficient separation of photo-generated carriers in water splitting. Based on first-principles calculations, electronic properties and a photocatalytic mechanism of a GeC/HfS2 van der Waals (vdW) heterostructure are systematically explored. From the analysis of band arrangement and the built-in electric field, the heterostructure, with an indirect bandgap of 0.40 eV, is demonstrated to be a typical direct Z-scheme system. Remarkably, there is also a 0.40 eV interlayer work function difference in the heterostructure, which is helpful to further drive carrier separation and enhance the water splitting ability by partially bending the redox potential of water. The Gibbs calculation shows that the GeC/HfS2 vdW heterostructure can achieve overall photocatalytic water splitting spontaneously under neutral conditions. Moreover, excellent visible light absorption ability (∼5×105 cm−1) and giant carrier mobilities (5823 cm2 V−1 s−1) also make GeC/HfS2 heterostructure highly competitive in numerous photocatalytic materials and optoelectronic devices. The bandgap can be flexibly adjusted by biaxial strain, enabling a wider application of the heterostructure. All these significant properties not only demonstrate the great application potential of GeC/HfS2 heterostructure as photocatalysis but also provide ideas for designing novel electric field-enhanced heterostructures.