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

Abstract

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 photoexcited 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.