Synergistic Plasmon-Piezoelectric Enhancement in Ag-Modified Gd and Zr Co-doped BiFeO3 Nanoparticles for Piezo-photocatalysis Degradation of Ofloxacin

Abstract

This study presents a novel strategy to significantly enhance the piezocatalytic performance of BiFeO₃ for antibiotic degradation by integrating cation co-doping and noble metal decoration. To address the inherent limitations of rapid charge recombination and insufficient active sites in pristine BiFeO₃, Gd, and Zr co-doped BiFeO₃ (BGFZ9) NPs were first synthesized via a sol-gel method. Subsequently, Ag NPs were uniformly deposited on the BGFZ9 surface through a facile photochemical reduction process to construct Ag/BGFZ9 nanocomposites. Comprehensive characterizations including XRD, XPS, TEM, and VSM confirmed the successful formation of the perovskite structure, uniform dispersion of Ag NPs, and tailored magnetic properties. The optimized Ag2/BGFZ9 catalyst demonstrated remarkable piezocatalytic and piezo-photocatalytic activity towards ofloxacin, achieving degradation efficiencies of 82.54 and 86.98% within 120 min under ultrasonic and combined ultrasonic/visible-light irradiation, respectively. The corresponding first-order rate constants were 0.0147 and 0.0164 min^–1, representing a significant enhancement over the undoped and unmodified counterparts. The superior performance is attributed to the synergistic interplay of multiple factors: (1) the Gd/Zr co-doping induced lattice distortion and optimized band structure, enhancing the intrinsic piezoelectric response; (2) the formation of a Schottky junction at the Ag/BGFZ9 interface, which acted as an efficient electron sink to suppress charge carrier recombination; and (3) the LSPR effect of Ag NPs under visible light, which broadened light absorption and generated hot electrons. Radical trapping experiments and EPR spectroscopy identified \( \bullet {\kern 1pt} {\text{O}}_{2}^{ - }\) and \( \bullet {\kern 1pt} {\text{OH}}\) as the primary reactive oxygen species. The catalyst maintained 82.13% of its initial activity after five consecutive cycles, demonstrating excellent stability and magnetic recoverability. This work elucidates a synergistic piezoelectric-plasmonic coupling mechanism and provides a viable design principle for developing efficient, stable, and magnetically separable multiferroic catalysts for advanced oxidation processes in wastewater remediation.