Sonochemistry‐Guided Interfacial Coordination via Controlled Polyphenol Aggregation for Efficient Polyphenol/Bi ₂ WO ₆ Photoanode

ABSTRACT The construction of ordered interfacial structures in organic–inorganic heterojunction photoanodes for high‐efficiency photoelectrochemical (PEC) water splitting remains challenging due to kinetic mismatches between molecular assembly and interfacial coordination. Herein, a transformative sonochemical strategy is reported to overcome this bottleneck by utilizing the piezoelectricity of nanomaterials. Operating under non‐equilibrium conditions, this approach couples ultrasound‐induced cavitation with the self‐assembly of gallic acid (GA), enabling ultrafast, localized modulation on piezoelectric photoanode. Using a GA/Bi 2 WO 6 (BWO) model, the piezoelectric response directs GA‐derived assemblies onto the surface, forming an ordered heterojunction. By precisely tuning the sound pressure level, competing pathways are balanced: the high‐energy‐barrier self‐assembly of GA in solution is suppressed, while the lower‐energy‐barrier coordination between deprotonated GA and surface Bi 3+ ions is promoted. This yields a homogeneous 2 nm amorphous GA layer on GA 0.05 /BWO heterojunction with exposure of electron‐withdrawing groups (‐COOH). This ordered GA/BWO heterojunction is facilitating photogenerated carrier separation and suppressing recombination by creating efficient hole transfer channels. The optimized GA 0.05 /BWO photoanode is achieving a photocurrent density of 196.9 µA·cm −2 at 1.23 V RHE (18.6 times of BWO), with separation and injection efficiencies reaching 49.0% and 50.9%, respectively. This work is introducing a paradigm shift, utilizing intrinsic properties as feedback for the rational design of functional materials.