Boosting carrier dynamics of BiVO4 photoanode via heterostructuring with ultrathin BiOI nanosheets for enhanced solar water splitting.

[Display omitted] • The oxygen vacancies introduced into BiVO 4 through the reduction of V⁵⁺ to V⁴⁺ by I⁻. • The ultrathin BiOI nanosheets and BiVO 4 formed the type II heterojunction. • Oxygen vacancies and built-in electric field synergistically boost the carrier dynamics. Bismuth vanadate (BiVO 4) has been one of the most promising candidates for solar water splitting while still suffers from poor bulk charge transport that limits its solar to hydrogen conversion efficiency. We demonstrate in this work an efficient strategy for boosting bulk charge transport of BiVO 4 through the facile impregnation of as-prepared BiVO 4 photoanode in the precursor solution of ultrathin BiOI nanosheets. Such impregnation creates increased oxygen vacancies in the bulk of BiVO 4 through the reduction of V⁵⁺ to V⁴⁺ by I⁻, which greatly improves bulk separation efficiency for BiVO 4 -BiOI up to 65.9 % at 1.23 V RHE from the original 51.9 % of pure BiVO 4. Moreover, the decoration of the BiOI nanosheets on BiVO 4 photoanode is also beneficial for addressing the carrier dynamics at surface due to the matched energy levels of BiOI nanosheets and BiVO 4. The introduced plenty of oxygen vacancies in the bulk of BiVO 4 and the built-in electric field in BiVO 4 -BiOI synergistically improve the photocurrent density at 1.23 V RHE up to 3.88 mA cm^-2. We believe that such facile impregnation strategy will pave an alternative way to the development of highly efficient BiVO 4 photoanode. [ABSTRACT FROM AUTHOR]