Well-Crystallized α-FeOOH Cocatalysts Modified BiVO₄ Photoanodes for Efficient and Stable Photoelectrochemical Water Splitting

Monoclinic bismuth vanadate (BiVO4) is a potential photoanode for photoelectrochemical (PEC) water splitting, but it suffers from poor electron–hole separation. Here, a reproducible chemical bath deposition method was employed to immobilize well-crystallized α-FeOOH on the BiVO4 photoanode, resulting in a nearly unity faradaic efficiency and more than 21-fold higher solar to fuel conversion efficiency compared with pure BiVO4 photoanode. The precursor containing Fe2+ ions has been identified to be crucial for preparation of this well-crystallized α-FeOOH cocatalyst. Systematic studies revealed that the high efficiency and excellent stability of the α-FeOOH(P-II)/BiVO4 photoanode were attributed to the well-crystallized α-FeOOH that facilitated the charge carrier separation and transfer for PEC water splitting. Our findings thus not only demonstrated a highly stable and efficient photoanode for PEC water splitting but also provided a promising strategy for the rational design of well-crystallized α-FeOOH.