Novel Ferroelectric Mediated Dual S‐scheme Heterojunction with Multiple Built‐in Electric Fields for Enhanced Photoelectrochemical Seawater Splitting

Abstract Photoelectrochemical (PEC) seawater splitting is promising for direct utilization of solar energy and ocean resources for H 2 production, but encounters challenges like difficult separation and recombination between holes and electrons. Herein, a dual S‐scheme TiO 2 /SrTiO 3 /C 3 N 4 (TiO 2 /STO/CN) heterojunction is in situ synthesized to construct a self‐supporting three‐phase system for PEC seawater splitting. The dual S‐scheme heterojunction photoanode has high electron‐hole pair separation quality and low recombination efficiency, and exhibits excellent catalytic performance. It achieves a photocurrent density of 6.32 mA·cm −2 at 1.23 V and a high applied bias photon‐to‐current efficiency (ABPE) of 1.90%, which are much higher than that of the pristine TiO 2 photoelectrode and other reports. The remarkable PEC activity of TiO 2 /STO/CN is attributed to the effective charge separation driven by the multiple built‐in electric fields within the ferroelectric mediated dual S‐scheme heterojunction. The photogenerated carrier transfer pathways are discussed with multifarious methods such as band structure analysis, KPFM, EPR, and DFT calculations. It provides a perspective for constructing high‐performance photocatalysts.