High photoelectrochemical activity and stability of Au-WS2/silicon heterojunction photocathode

Abstract

Although silicon has been widely employed as light harvesting antenna in photocatalysts due to its cost advantage, it suffers from low efficiency and poor stability due to photocorrosion of Si. To overcome this problem, a heterojunction photocathode was produced by coating a WS2 thin-film on p-type Si. Our proposed method can further improve the photocatalytic activity and stability. The homogeneous WS2 films with large surface area and tens-of-nanometers in thickness were prepared through magnetron and post-annealing process. This film not only functions as a protective layer to isolate the Si from the harsh electrochemical environment, but also forms a junction at the interface between WS2 and p-type Si to facilitate the charge separation and transport processes. Additionally, further enhancement of visible photocatalytic performance was achieved by depositing Au film on WS2/p-Si through thermal evaporation and the highest value of the photocurrent intensity achieved is up to ~ 4.5 μA/cm2 at 0 V versus Ag/AgCl. Besides, photoelectrochemical instability of WS2/p-Si electrodes can be minimized by adding Au coating. Our results suggest that adding the Au-WS2 on p-Si can benefit carrier separation and providing physical protection of the Si layer. Therefore, it can further improve the overall photocatalytic activity and stability.