Local polarization-piezoelectric field promotes water dissociation for efficient fluorinated pollutants defluorination.

Abstract

Active hydrogen radicals (•H) from water dissociation hold great promise for the defluorination of perfluorooctanoic acid (PFOA). However, the mechanism governing •H generation under a local polarization piezoelectric electric field (LPPEF) remains insufficiently explored in borate-based piezocatalysts, which hinders an understanding of the piezocatalysis-driven water dissociation. Herein, we investigated piezocatalyst, Sr2B5O9Cl (SBOC) and its KBH4-impregnated derivative (B-SBOC) in PFOA defluorination. Under ambient conditions, B-SBOC achieves a degradation rate constant of 1.34 × 10-2 min⁻1 for an initial PFOA concentration at 24.2 μM, along with a synchronous defluorination ratio of 78% within 120 min, representing a 2.5-fold enhancement over pristine SBOC. The incorporated electron-deficient boron atoms serve as Lewis acid sites, which not only enhance surface hydrophilicity and reverse the surface charge to facilitate PFOA adsorption but, more critically, intensify the LPPEF. The strengthened LPPEF promotes the preferential adsorption of •OH, thereby effectively suppressing •OH/•H recombination. This accelerates the kinetics of water dissociation and promotes subsequent •H dominated H/F exchange reactions, boosting efficient PFOA defluorination. This work provides fundamental insight into the LPPEF dominated radical separation process and offers a potential strategy for designing highly efficient piezocatalytic systems for recalcitrant fluorinated pollutants remediation.