Sonochemistry-Guided Interfacial Coordination via Controlled Polyphenol Aggregation for Efficient Polyphenol/Bi₂WO₆ Photoanode

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/Bi₂WO₆ (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 Bi³⁺ 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.