A Bifunctional Ferroelectric Catalyst Enabling Simultaneous Photoelectrochemical Water Oxidation and Two‐Electron Oxygen Reduction

ABSTRACT Photoelectrochemical (PEC) systems provide a sustainable approach to producing value‐added chemicals by synergizing photo‐ and electrochemical processes. Beyond conventional strategies that focus on tuning intrinsic material properties, external field modulation emerges as a promising avenue for steering chemical reactions. Herein, a bifunctional ferroelectric catalyst Ba _0.7 Sr _0.3 TiO ₃ (BSTO) is demonstrated on both photoanode and cathode to concurrently promote water oxidation and two‐electron oxygen reduction reaction (2e ⁻ ORR). BSTO‐coated α‐Fe ₂ O ₃ is first selected as a model photoanode with enhanced PEC water oxidation performance upon controlled electric poling. Mechanistic studies indicate that ferroelectric polarization effectively tunes the band bending at the Fe ₂ O ₃ /BSTO interface, thereby facilitating charge separation. The general applicability of this strategy is further demonstrated with other metal oxide photoanodes, including TiO ₂ and BiVO ₄ . On the cathode side, ferroelectric polarization induces a transition of the O ₂ adsorption configuration from the Yeager‐ to the Pauling‐type, which not only accelerates interfacial charge transfer kinetics but also favors the 2e ⁻ ORR pathway, resulting in an increased H ₂ O ₂ production rate. These findings highlight ferroelectric modulation as a versatile strategy for the design of high‐performance (photo)electrocatalytic systems.