Two-dimensional heterojunction SnS2/SnO2 photoanode with excellent photoresponse up to near infrared region

Two-dimensional (2D) semiconductor materials have attracted much attention in solar energy utilization due to their unique structure and excellent photoelectrical properties. However, the band bending in the 2D materialsbased photoelectrodes is limited when the thickness of 2D flakes are too thin, which normally leads to weak driving force for charge separation and transfer. Constructing heterojunction is an effective way to enhance the band bending by creating additional space charge layer in semiconductors. Herein we intentionally introduce a 2D SnS2 layer on SnO2 nanoflakes to design a new class of 2D heterojunction of SnS2/SnO2. The low lattice mismatch of two materials leads to intimate heterojunction contact with well-matched energy band alignment, which efficiently promote the charge carrier separation of SnS2 photoelectrodes. Moreover, the conductive SnO2 provides a good pathway for electron collection. Consequently, the photocurrent density of the SnS2/SnO2 heterojunction photoanode is largely improved by 2.8 times to 0.7 mA cm(-2) at 1.23 V vs RHE compared to the pristine SnS2, which also shows significantly improved photocurrent density than others for wet-chemically prepared SnS2 based photoanodes. Considerable near infrared (NIR) light photoresponse is also observed in the SnS2/SnO2 heterojunction which is mainly induced by the defects.