Mott–Schottky Interface in Bi₂Fe₄O₉/Ag Boosting Piezocarriers Separation for Hydroxychloroquine Degradation

Piezocatalytic advanced oxidation has been regarded as a promising and low energy cost strategy for water decontamination. Bi₂Fe₄O₉ (BFO) has been identified as a promising piezocatalyst due to its impressive ferroelectricity, but the low carrier separation efficiency limits its further development. This study constructs BFO/Ag Mott–Schottky heterojunction via a facile in situ photoreductive growth method, which establishes a built-in electric field to facilitate carrier separation. This enhanced carrier separation promotes the generation of active species in the reaction system. The experiments and theoretical calculations support that piezocarriers separation is facilitated by the Mott–Schottky heterojunction and that Fe sites serving as active centers to generate reactive species via the oxygen reduction reaction pathway. Moreover, BFO/Ag powder was immobilized in a polyvinylidene fluoride (PVDF) membrane via the phase inversion method and achieved 99% hydroxychloroquine (HCQ) removal in a continuous-flow membrane reactor by harnessing hydraulic energy within 30 min, offering a potential solution to practical limitations such as powder catalyst loss and secondary pollution, while enabling integration with wastewater treatment systems. This study offers a new strategy for enhancing the catalytic activity of piezocatalysts and the efficient degradation of HCQ, which may inspire the development of piezocatalysts for environmental application.