Construction of p-n heterostructured BiOI/TiO2 nanosheets arrays for improved photoelectrochemical water splitting performance.

[Display omitted] • Energy band structure of BiOI-TiO 2 heterojunction helped to improve PEC performance. • The p-type semiconductor BiOI has visible light absorption. • The built-in electric field of p-n heterojunction, which provides a driving force promoting the separation of photoexcited carriers. • The concept of p-n heterojunction, and type-II energy structure were simultaneously applied for a synergetic effect. The construction of p-n heterojunction is one of the effective strategies to improve the spatial charge separation due to built-in electric field. In this study, the p-type BiOI ultrathin 2D nanoplates decorated n-type TiO 2 nanosheets arrays (TNS) heterojunction photoanode was successfully fabricated through hydrothermal methods. The photocurrent density achieved for optimized BiOI/TNS photoanode was 0.54 mA cm−2 at 1.23 V vs. RHE, which is 15 times higher than that of unmodified TNS photoelectrode (0.036 mA cm−2) under simulated sunlight irradiation without any cocatalyst. In addition, the onset potential of BiOI/TNS photoanodes has a certain negative shift from 0.5 to 0.3 V, which can demonstrate BiOI/TNS photoanodes possesses better catalytic activity and kinetics for water oxidation. The excellent photoelectrochemical activity of BiOI/TNS could be attributed to the type-II energy structure of BiOI/TiO 2 photoanode, the built-in electric field of p-n heterojunction, and TiO 2 nanosheets arrays with high exposed {0 0 1} facets. [ABSTRACT FROM AUTHOR]