Defect-Polarization Synergy Unlocks Sustained Nonradical Piezocatalysis via Iron Redox Cycling

Piezocatalysis promises sustainable water purification but remains constrained by ephemeral and nonselective radical pathways in complex aqueous environments. Herein, this study reports a defect-engineered BiFeO₃ piezocatalytic peroxymonosulfate activation system, which manifests efficient catalytic dynamics through dual nonradical oxidation pathways involving high-valent Fe(IV) = O species and piezo-induced holes. Experimental and theoretical analyses unveil a closed-loop Fe(II)/Fe(III)/Fe(IV) = O redox cycle sustained by the synergy of oxygen vacancy defects and piezoelectric polarization, enabling persistent nonradical oxidation. This system achieves over 99% bacterial inactivation within 30 min and unprecedented pollutant degradation rates (e.g., k = 0.174 min⁻¹ for Sulfamethoxazole, 0.477 min⁻¹ for Rhodamine B), outperforming state-of-the-art radical-based BiFeO₃ systems by 2−40 fold. The catalyst retains robust activity across broad pH ranges, anion-rich environments, and real water matrices. This work not only advances the mechanistic understanding of piezocatalysis beyond conventional radical pathways but also establishes a design framework for durable, efficient, and self-sustaining piezocatalytic systems for scalable water purification.