Two-dimensional penta-SiAs2: a potential metal-free photocatalyst for overall water splitting

Photocatalytic water splitting, as an artificial photosynthesis process for producing clean hydrogen energy, has recently attracted extensive attention due to its bright prospects for solving the shortage of fossil energy and environmental crisis. However, it is still challenging to achieve highly efficient overall water splitting because of the unsuitable electronic structure and the strong dependence on the noble metal co-catalysts to date. The development of photocatalytic water splitting is therefore immensely urgent to enlarge the uptake of photocatalysts by exploring novel compounds. Herein, we propose a novel two-dimensional (2D) pentagonal SiAs2(penta-SiAs2) photocatalyst suitable for water splitting based on first-principles calculations. Using a hybrid functional, we demonstrate the bandgap of 2D penta-SiAs(2)to be 2.35 eV, and its band-edges perfectly stride the redox potential of water. Most importantly, this material possesses both highly desirable carrier mobilities and strong light absorption in the visible and ultraviolet (UV) regions, which are superior to those of most previously reported 2D materials. Furthermore, the free energies suggest that hydrogen and oxygen evolution reactions are feasible with penta-SiAs2. These extraordinary characteristics make penta-SiAs2 a promising 2D material for photocatalytic water splitting and provide a possible route for the future experiment scheme.