Recyclable CoFe2O4 modified BiOCl hierarchical microspheres utilizing photo, photothermal and mechanical energy for organic pollutant degradation

Taking advantage of multiple energy sources is an effective way to enhance the catalytic efficiency of a catalytic system. Here, through rational design, we fabricated CoFe2O4 modified BiOCl hierarchical microspheres (CFO-BiOCl), which not only can make full use of photo, photothermal and mechanical energy but also can be easily recycled from liquid solutions. Photocatalytic activity measurement showed that CFO-BiOCl samples possessed outstanding photocatalytic activity, evident with 99% of rhodamine B decomposed in 5 min and 90% of tetracycline hydrochloride degraded in 10 min under full-spectrum light irradiation. Furthermore, piezo-/photocatalytic degradation rates of tetracycline hydrochloride, bisphenol A and phenol were around 2, 3 and 8 times higher than photocatalytic degradation rates under low-intensity light irradiation. Recycling tests showed that the piezo-/photocatalytic activity of CFO-BiOCl hardly decreased after 5 cycles. The excellent photocatalytic performance of CFO-BiOCl catalysts can be attributed to suitable band alignment of CoFe2O4 and BiOCl and photothermal effect that elevates organic pollutant molecules into a more active state. The generation of piezoelectric field in BiOCl crystals, providing strong driven force for the separation of photo-induced electrons and holes, gives rise to the high piezo-/photocatalytic efficiency. This work may bring a design pattern to fabricate catalysts that can utilize multiple energy sources and give a thorough discussion in the catalytic mechanism.