Polarization-enhanced piezo-photocatalysis over hollow-sphere Bi4Ti3O12: Structure-property relationship and degradation mechanism

Abstract

Tetracycline hydrochloride (TCH) exists in various forms in aqueous solution due to pH changes, which not only alters the reactivity of TCH, but also affects the process of reactive oxygen species (ROS) attacking the molecule. Therefore, the rational design of piezo-photocatalytic materials coupled with a comprehensive understanding of the degradation mechanisms of various TCH species constitutes a critical approach to addressing tetracycline antibiotic contamination. In the design and preparation of piezo-photocatalysts, controlling the oxygen vacancy concentration is crucial as it governs the coupling efficiency between piezoelectric response and photocatalytic activity, as well as the strength of spontaneous polarization. Meanwhile, the morphology of the material is a key factor influencing the migration pathways of charge carriers. In this work, hollow spherical Bi₄Ti₃O₁₂ was synthesized using an inorganic titanium source, demonstrating exceptional piezo-photocatalytic activity. The degradation rate was 1.57 and 5.29 times higher than that of traditional spherical and plate-like morphologies, with a rate constant of k = 0.127. In an innovative approach, density functional theory calculations of local softness and hyper-softness were employed to analyze the reactivity changes of TCH in its different deprotonated states toward reactive oxygen species. Combined with molecular electronegativity analysis, the factors influencing the degradation efficiency were identified. This study provides a solid foundation for developing efficient and environmentally friendly piezo-photocatalysts and offers new insights into the degradation mechanism of TCH.