Piezo-catalytic in-site H2O2 generation and activation across wide pH range to drive hydroxyl radical-mediated pollutant degradation

Hydroxyl radicals (·OH) is one of the most important reactive oxygen species (ROSs) for organic pollution controlling in advanced oxidation processes, while its production suffers from numerous H₂O₂ addition and narrow pH range in generally used Fenton reaction. Herein, we demonstrate a BiOIO₃ (BIO) piezo-catalyst loaded with γ-FeOOH nanoparticles (FNPs) (BF) that can convert O₂ to ·OH in a wide pH condition without external H₂O₂ addition under ultrasonication. It is found that the robust interfacial interaction facilitates rapid electron migration from BIO to FNPs, enabling two-electron O₂ reduction into H₂O₂ at the FNPs site, while the leaving behind piezo-holes to perform two-electron water oxidative H₂O₂ generation on BIO. Because the electron-rich nature of FNPs favors the H⁺ adsorption that contributes a surface acidic micro-environment, the produced H₂O₂ can be in-situ catalyzed into ·OH in either neutral or even alkaline conditions with a great stability. Finally, the optimal BF can achieve either an impressive ·OH yield of 38.1 µM h^-1 or a high H₂O₂ yield of 522.0 µM h^-1 by regulating the FNPs loading mass, which enables dual capabilities of rapid organic pollutants degradation and H₂O₂ production in a wide pH condition.