Construction of Bi2S3/BiVO4/TNbO photoanode with energy band and interface engineering for efficient photoelectrochemical water splitting

Rational design nano-photoanodes with favorable optical absorption and charge separation-transfer played an important role in enhancing photoelectrochemical (PEC) water splitting for boosted solar-to-hydrogen (STH) conversion. As for the sluggish oxygen evolution reaction (OER) dynamics, we constructed a ternary Ti-based composite photoanode (BS/BVO/TNbO) with effective carrier management toward efficient photoelectrochemical water oxidation. Microstructure analysis demonstrated that the positive shift of valence-conduction band through Nb-doping made the energy band well-matched with BiVO4 and Bi2S3. Sequential loading of BiVO4 and Bi2S3 substantially extended the absorption edge from 382 to 550 nm. Meanwhile, the optimized hetero-interface enabled photogenerated electrons gathered in Nb-doped TiO2 (TNbO) nanotubes and the holes transferred to Bi2S3 effectively. Bulk-phase Nb-doping promoted fast carrier transport within and across TNbO photoanodes, coupling BiVO4 and Bi2S3 further accelerated charge separation-transfer process. BS/BVO/TNbO photoanodes showed excellent charge separation efficiency (ηsep) of 38 %, which was much higher than pristine TiO2 (29 %). PEC measurements illustrated that the yielding photocurrent was favorably improved to 3.4 mA/cm2 at 1.23 V vs RHE, and STH efficiency (1.53 %) was 7.3 times that of pristine system. This work involved energy band and interface engineering of ternary Ti-based photoanode, which may contribute to designing high-efficiency photoanodes with effective carrier management in driving solar water splitting.