Structure and Band Alignment Engineering of CdS/TiO2/Bi2WO6 Trilayer Nanoflake Array for Efficient Photoelectrochemical Water Splitting

Designing photoanode materials with desirable architecture and band alignment is essential for boosting photoelectrochemical (PEC) water splitting performance. Herein, a trilayer CdS/TiO2/Bi2WO6 guest-host photoanode is designed and fabricated, in which highly-porous Bi2WO6 nanoflake array serves as the host skeleton, while CdS nanoparticles function as superb visible light absorber. An ultrathin TiO2 interlayer is rationally inserted between Bi2WO6 and CdS, which not only assists the uniform growth of CdS, but also serves as a band-matching semiconductor to promote the charge transport. By optimizing the thickness of TiO2 layer, the resulting trilayer photoanode exhibits higher PEC performance (2.62/4.91 mA cm(-2) at 1.23 V vs. reversible hydrogen electrode without/with the presence of hole scavenger) under AM 1.5G illumination compared with pristine CdS film. The enhancement of PEC performance is attributed to the enlarged surface area and superior light harvesting ability of the 3D nanoflake nanostructure, and improved charge transport efficiency resulting from the cascaded energy level structure.