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

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.