A promising Ag_2CrO_4/LaFeO_3 heterojunction photocatalyst applied to photo-Fenton degradation of RhB

摘要

Ag2CrO4 nanoparticles (10-35 nm) were assembled onto LaFeO3 nanoparticles (20-60 nm) via a facile chemical precipitation method to form novel Ag2CrO4-LaFeO3 heterojunction composite photocatalysts. The prepared Ag2CrO4-LaFeO3 composites were characterized by XRD, SEM, TEM, XPS, BET, UV-vis DRS, PL spectroscopy and EIS and photocurrent response. The TEM result clearly shows that Ag2CrO4 particles are decorated onto LaFeO3 particles to form Ag2CrO4-LaFeO3 heterojunction. Compared to bare LaFeO3, the 10%Ag2CrO4-LaFeO3 composite exhibits a slightly increased BET specific surface area, increased photocurrent density, decreased charge-transfer resistance and decreased PL emission peaks. Using simulated sunlight as the light source and in the presence of H2O2, the photo-Fenton performance of the composite photocatalysts toward the degradation of RhB was investigated, revealing that they manifest significantly enhanced photo-Fenton degradation of RhB when compared with bare LaFeO3 and Ag2CrO4. Among the composite photocatalysts, 10%Ag2CrO4-LaFeO3 exhibits the highest photo-Fenton activity, which is about 3.1 and 2.5 times higher than that of bare LaFeO3 and Ag2CrO4, respectively. This is attributed to the fact that the composite photocatalysts have highly efficient separation of photogenerated electron-hole pairs due to the formation of Ag2CrO4-LaFeO3 heterojunctions. Active species trapping experiments and center dot OH detection experiments were carried out, from which it is concluded that center dot OH radicals are the dominant reactive species causing the dye degradation. A synergistic mechanism was proposed to elucidate the enhanced photo-Fenton activity of Ag2CrO4-LaFeO3 heterojunction composites.