Remarkably enhanced piezo-photocatalytic performance of Z-scheme Bi2WO6/Black TiO2 heterojunction via piezoelectric effect

Current photocatalytic efficiency is quite restricted due to serious e−-h+ pairs recombination. Combining piezoelectric effect into photocatalysis is an effective strategy to improve catalytic performance. Here, a rationally designed Bi2WO6/Black TiO2 (Bi2WO6/B–TiO2) heterojunction to enable a high piezo-photocatalytic activity via piezoelectric effect is reported. The degradation efficiency of cationic dye Rhodamine B (RhB) over optimized Bi2WO6/B–TiO2 reaches 98.43% in 60 min under simultaneous ultrasonication and sunlight, which is higher than the total of those by independent photocatalysis (54.23%) and piezocatalysis (26.33%). Moreover, this hybrid Bi2WO6/B–TiO2 piezo-photocatalyst also shows promising degradation of anionic dye methyl orange (MO), methyl blue (MB) and antibiotics (diclofenac sodium, DCF) under sunlight and ultrasonication. A built-in polarization field is generated inside the Bi2WO6 nanosheets by ultrasound, which can accelerate effective segregation of photogenerated e−-h+ pairs in Bi2WO6 and B–TiO2, thereby enhancing the overall activity of the heterojunction. Furthermore, radical trapping and photodeposition experiments, EPR and VB-XPS spectra directly prove that the Bi2WO6/B–TiO2 heterojunction is a Z-scheme system. Finally, a Z-scheme piezo-photocatalytic mechanism for Bi2WO6/B–TiO2 is rationalized. This work offers a promising way to design high-efficient catalysts by combining piezoelectric effect into photocatalysis.