Self-regulation of Lewis acid sites on FeOCl toward piezo-self-Fenton reaction for continuous hydroxyl radicals generation

Clarifying the structure-property relationship is critical to the design of high-performance piezocatalysts. Herein, with iron oxychloride (FeOCl) as the model piezocatalyst, a systematic investigation into the evolution of surface properties by the induced piezopotential is performed. Except for the promotion in carrier dynamics, the induced piezopotential also achieve in-situ regulation of the surface Lewis acid sites. The surface Lewis acidity of FeOCl, as well as other classic piezocatalyst such as BaTiO3, BiTiO3, and BiFeO3, is dynamically enhanced under the application of mechanical stress. Consequently, the activation and consecutive conversion of the O2 molecule, whose Lewis basicity is weaker than H2O2, is realized on the FeOCl piezocatalyst. The heterogeneous Fenton activity of FeOCl catalyst is upgraded into a more advanced piezo-self-Fenton activity, producing hydroxyl radicals efficiently under ultrasonic vibration (556.8 µmol g−1 h−1). The FeOCl piezo-self-Fenton system exhibits exceptional broad-spectrum degradation efficiency, operational stability, and scalability for the treatment of pharmaceutical wastewater. This work highlights the in-situ regulation of surface property by the induced piezopotential as a new feature for the piezocatalysts, which contributes to the enhancement of piezocatalytic activity and even changes the reaction pathway. Designing efficient piezocatalysts requires understanding how mechanical stress alters surfaces. This study shows stress-induced electric potentials boost surface acidity, activate oxygen, and enable hydrogen-peroxide-free pollutant degradation.