Spontaneous enhanced photocatalytic overall water splitting on AlO/WSi2N4 vdW heterojunction

Abstract

Completely achieving spontaneous water splitting without sacrificing co-catalysts poses a significant challenge, as factors such as electrical, optical, and catalytic activity can limit the conversion efficiency of solar energy to hydrogen. Herein, we propose a type-II van der Waals heterostructure composed of vertically stacked AlO and WSi2N4, and systematically investigate its mechanism and potential for catalyzing water splitting. Photon-induced photocatalytic water splitting takes advantage of the staggered energy bands of the heterojunction, effectively promoting the separation of photogenerated carriers and thus enhancing catalytic efficiency. In neutral water environment, the band edge position of AlO/WSi2N4 aligns with the redox potential required for water decomposition. Thermodynamic analysis of the oxygen and hydrogen evolution reactions indicates that the external potential provided by photogenerated carriers is expected to trigger spontaneous water decomposition. Moreover, with its high electron mobility (4800.62 cm2/Vs) and a solar-to-hydrogen energy conversion efficiency of up to 19.98 %, the AlO/WSi2N4 heterojunction demonstrates substantial potential as a photoelectric catalyst. This research introduces a promising avenue for efficient photocatalytic production of clean energy.