Electric field induced band modulation of WS2-GeC heterostructures for efficient photocatalytic water splitting: A density functional theory study

Nowadays, the development of composite materials has greatly stimulated people's interests to pursue a better utilization of solar light for efficient water splitting. The modulation of materials' properties for some specific purposes through manipulating external conditions has come into wide use and can provide many opportunities to promote a certain performance. In this work, we present a systematic computation study of the hybrid WS2-GeC composite that can realize a better response to solar energy and significantly strengthen the carriers' separation, achieving a higher efficiency for the water splitting reaction. A comprehensive calculation shows that the bandgap variation of WS2-GeC heterostructure exhibits an interesting response to the applied electric field compared with freestanding structures and an obvious redshift of the absorption edge is observed. The electronic structure of the interface reveals that the WS2-GeC is a typical type-II heterostructure with the photoinduced electrons/holes transfer to the conduction/valence band of WS2 from the conduction/valence band of GeC, respectively. All the above suggest that the WS2-GeC composite has significant advantages for water splitting. After the electric field applied, this heterostructure would gradually meet the standard thermodynamic requirements of a sustainable water splitting reaction for suitable band edge positions with respect to (w.r.t) the water redox levels. In brief, a convictive theoretical approach was presented to reveal the evolution of high activity for water splitting achieved by WS2-GeC heterostructures. We believe the corresponding theoretical methodology will arouse a further interest in other 2D based composite structures. This work provides a flexible and feasible approach of electric field engineering for composites applied in water splitting.