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

Photoelectrochemical (PEC) seawater splitting is promising for direct utilization of solar energy and ocean resources for H₂ production, but encounters challenges like difficult separation and recombination between holes and electrons. Herein, a dual S-scheme TiO₂/SrTiO₃/C₃N₄ (TiO₂/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 TiO₂ photoelectrode and other reports. The remarkable PEC activity of TiO₂/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.