Improved photocatalytic activity of SrBi2Nb2O9 for the degradation of ciprofloxacin hydrochloride via piezoelectric-enhanced charge transfer

Piezo-photocatalysis is an emerging photocatalytic technology in which the piezoelectric electric field drives photogenerated carriers to separate, thereby improving the photocatalytic activity of the catalyst. Herein, solid phase and one-step molten salt processes were used to prepare SrBi₂Nb₂O₉ (SBN) powders with granular and sheet morphologies, respectively. The influence of micromorphology on the piezo-photocatalytic performances of SBN was determined by degrading ciprofloxacin hydrochloride (CIP). SBN nanosheets demonstrate remarkable piezo-photocatalytic performance, achieving an 89.13% CIP degradation rate in 60 min and an apparent rate constant of 34.73 × 10⁻³ min⁻¹. This performance is approximately 2.65 times higher than that of granular SBN and outperformed many recently reported piezo-photocatalysts under similar experimental conditions. Free radical trapping techniques, electron spin resonance spectroscopy and liquid chromatography-mass spectrometry are utilized to study the potential paths and mechanisms of CIP degradation. Piezoresponse force microscopy and finite element simulation show that the piezo-response of SBN nanosheets is significantly higher than that of granular SBN. SBN nanosheets achieve high degradation efficiency due to their optimized conduction band positions and enhanced piezoelectric effect, facilitated by the two-dimensional nanosheet structures. In this work, the piezoelectric internal electric field of piezoelectric catalysts can be increased by tuning the catalyst morphology, which points to a possible direction for the production of high-performance piezoelectric catalysts.