Tunable Ferroelectric Polarization in BaTiO ₃ Coupled with Zn _0.5 Cd _0.5 S Quantum Dots for Efficient Solar‐Driven Hydrogen Evolution

Abstract Integrating ferroelectric materials with semiconductor photocatalysts offers a groundbreaking strategy to enhance solar‐driven hydrogen production by improving charge separation and transfer efficiency. Herein, a synergistic system is developed by coupling the tunable ferroelectric polarization of BaTiO ₃ (BTO) with a Z‐scheme heterojunction in Zn _0.5 Cd _0.5 S quantum dots (ZCS QDs). The strong and adjustable built‐in electric field generated by BTO effectively drives carrier separation, enhances interfacial band bending, and mitigates the excitonic effects commonly observed in QDs, facilitating directional charge transfer. Mechanistic insights, validated by in situ X‐ray photoelectron spectroscopy (XPS) and Kelvin Probe Force Microscopy (KPFM), highlight the pivotal role of ferroelectric polarization in modulating carrier dynamics and interfacial interactions. These attributes, resulting from the synergistic effects of ferroelectric polarization and the Z‐scheme heterojunction, enable the ZCS QDs/BTO composite to achieve an outstanding hydrogen evolution rate of 0.83 mmol g ⁻¹ h ⁻¹ , surpassing pure BTO and ZCS QDs by factors of 20.8 and 1.7, respectively. Notably, external polarization further amplifies hydrogen production to 1.19 mmol g ⁻¹ h ⁻¹ , representing a remarkable 143% increase compared to the pristine system and showcasing the pivotal role of polarization‐enhanced built‐in electric fields in photocatalysis. This work presents a novel pathway for designing advanced photocatalysts, providing promising prospects for sustainable hydrogen production.