Synthesis of Host‐Guest Hematite Photoelectrodes for Solar Water Splitting

Abstract Hematite (α‐Fe₂O₃) is a promising semiconductor for photoelectrochemical (PEC) water splitting, due to its abundance, low‐cost and excellent stability. However, the efficiency of α‐Fe₂O₃ photoelectrodes has been limited by its low hole mobility and fast electron‐hole recombination. Host‐guest architectures have emerged as a suitable design, which involves the use of a nanostructured collector for high solar absorption while maintaining an ultrathin absorber layer for better charge transport. In this study, a thin mesoporous SiO₂ host template coated with a conductive thin layer of TiO₂ was optimized to support the α‐Fe₂O₃ film. The α‐Fe₂O₃ thin layer was deposited by spray pyrolysis and then coated with a FeNiOOH co‐catalyst. A photocurrent improvement of ca. 85% over planar α‐Fe₂O₃ thin film reference was registered demonstrating the potential of this host‐guest approach.