Fabrication of Z-Scheme WO3/KNbO3 Photocatalyst with Enhanced Separation of Charge Carriers

Z-Scheme photocatalysts as a research focus perform strong redox capability and high photocatalytic performance. WO₃/KNbO₃ photocatalysts were fabricated by ball milling method, and performed higher photocatalytic activity in liquid degradation(rhodamine B, methylene blue and bisphenol A), compared with WO₃ or KNbO₃ monomer. This is due to that Z-scheme heterojunction is formed between WO₃ and KNbO₃, and the holes photo-excited in valence band of KNbO₃ are quickly combined with the electrons in conduction band of WO₃. The electrons accumulated in conduction band of KNbO₃ show high reducibility, thereby reducing O₂ to ^·O₂^-, and the holes in valence band of WO₃ show high oxidative to oxidize H₂O to ^·OH, respectively. Furthermore, it is proved by means of electron spin resonance(ESR) spectra, terephthalic acid photoluminescence probing technique(TA-PL), and UV-Vis absorption spectra of nitroblue tetrazolium. This work indicates that the fabrication of Z-scheme structure can improve the photocatalytic activity by efficiently separating the photogenerated electrons and holes in the photocatalytic reaction system, which is helpful to deeply understand the migration mechanism of photoexcited carrier(band-band transfer and Z-scheme transfer) in heterojunction photocatalysts.