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It is of great significance to understand the role of carrier in piezocatalysis of composites by studying the separation mode of carriers under dynamic polarization field. Herein, the separation and migration pathways of carriers under piezoelectric field are investigated by synthesizing heterojunctions with Bi2WO6 (BWO) nanosheets grown vertically on g-C3N4 (CN) coated ZnO nanorods and directly on ZnO. Compared with the photocatalysis, the piezocatalytic efficiency of Rhodamine B (RhB) by BWO/ZnO is significantly increased to 0.121 min−1, which indicated the polarization field promotes band tilt and Z-scheme formation. After introducing the CN interlayer, the piezocatalytic efficiency of BWO/CN/ZnO is further improved (0.217 min−1), which can be attributed to the unique core–shell structure with Z-scheme heterojunctions. This unique structure provides more active sites and excited carrier concentration, the intermediate layer CN also reduces the direct contact and recombination of electrons and holes controlled by polarization potential at the interface between BWO and ZnO. This work deeply analyzes the influence of carrier concentration, separation efficiency and transport process on piezocatalysis, which provides a reference for the design of efficient catalysts.

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.