Engineering surficial atom arrangement on α-SnWO4 film for efficient photoelectrochemical water splitting

Abstract

Achieving high-efficient photoelectrochemical (PEC) water splitting requires great charge transfer and excellent surficial reaction activity. To improve the PEC performance of α-SnWO4 photoanode, the atomic ratio of Sn and W on the surface of the α-SnWO4 photoanode is subtly adjusted by exposing the α-SnWO4 photoanode to a Sn2+ or H+-rich microenvironment, which is considered to determine the coordination environment of active sites. Increasing the content of tin on the surface can shift the work function to vacuum level and up-regulate the band-edge position, and the difference between the energy band of bulk and surface facilitates transferring photo-generated carriers to the surface. Besides, the tin atom as the actives sites is in favor of the water oxidation reaction compared to the W atom as termination. Thus, the faster charge separation and enhanced hole injection ability lead to the 1st-order reaction behavior of water oxidation on the tin-rich surface, while the tin-poor surface presents 2nd-order behavior. As a result, the Tin-rich SnWO4 photoanode (1.05 mA cm−2 at 1.23 V vs. RHE in 0.2 M KPi) shows 2 folds photocurrent of Tin-poor SnWO4 photoanode, which is the state-of-the-art photocurrent density of the material so far. This study provides a path for understanding the effect of surface termination, and the method for engineering surface can easy to be used for other metal oxide photoelectrodes.