Efficient photocatalytic degradation of polystyrene microplastics in water over core-shell BiO_2-x/CuBi₂O₄...

Microplastics pose a significant threat to ecosystems due to their persistence, mobility, and accumulation of toxins. Here, an excellent core-shell structure of BiO_2-x/CuBi₂O₄ p-n heterojunction (CBBO) with broad spectrum response was designed for efficient photodegradation of microplastics in water. Here, faced with the extremely difficult to degrade polystyrene plastic, the synthesized 5-CBBO with optimal photocatalytic activity caused severe damage to the surface of polystyrene (PS) after 15 d of full spectrum light irradiation. Compared to it, the damage to the PS surface by the photocatalytic reactions mediated by BiO_2-x and CuBi₂O₄ alone, and the irradiation of full spectrum light was negligible after 30 d. Besides, the analysis of Fourier Transform Infrared Spectroscopy and Gas Chromatography-Mass Spectrometry demonstrated that the photocatalytic degradation of PS by 5-CBBO leads to significant structural changes, including the breakdown of alkyl chains, aromatic rings, and the formation of oxygenated products such as benzoic acid, confirming its effectiveness in transforming PS into smaller, more environmentally benign compounds. Finally, the photo-electrochemical testing and theoretical calculations have revealed the reaction mechanism of enhanced carrier separation and improved photocatalytic activity. This study showcases photocatalysts as a clean technology to reduce microplastic pollution, while providing insights for designing more efficient systems.