| Lanthanum orthoferrite(LaFeO3)is a perovskite-type oxide with unique physicochemical properties.Its heterostructure photocatalyst has important application prospects in the field of photocatalysis and photo-Fenton performance.In this paper,we prepared Ag/LaFeO3,g-C3N4/LaFeO3 and Ag2CrO4/LaFeO3 composites,and the as-prepared composites were systematically characterized by XRD,SEM,TEM,XPS,BET,UV-vis DRS,PL spectroscopy,EIS and photocurrent response.The photocatalytic and photo-Fenton activity of the samples was evaluated by degrading Rh B under simulated-sunlight irradiation.The main research results are as follows:(1)Spherical LaFeO3 nanoparticles with an average size of 35 nm were synthesized by a polyacrylamide gel route.Ag nanoparticles of 8–18 nm in size were successfully decorated onto LaFeO3 particle surface by a chemical reduction method to yield Ag/LaFeO3 composites.It is found that LaFeO3 particles have two bandgap energies of 2.59 and 2.24 e V,which undergo almost no change when decorated with Ag nanoparticles.Compared to bare LaFeO3 particles,Ag/LaFeO3 composites exhibit an obviously enhanced photocatalytic activity.To clarify the role of active species in the photocatalysis,the effect of scavenger on the Rh B degradation as well as the ·OH yield was investigated.Based on the experimental results,·OH and ·O2-are suggested to be the main active species causing the dye degradation.(2)Z-scheme g-C3N4/LaFeO3 heterojunction photocatalysts were prepared by calcining the uniformly mixed g-C3N4 nanosheets and LaFeO3 nanoparticles at 300 °C for 1 h.SEM and TEM are demonstrated that LaFeO3 nanoparticles(average size: ca.35 nm)are uniformly assembled onto the surface of g-C3N4 nanosheets through chemical bonding,leading to the formation of g-C3N4/LaFeO3 heterojunctions.Compared to bare LaFeO3 and g-C3N4,the g-C3N4/LaFeO3 composites exhibit significantly enhanced photocatalytic and photo-Fenton degradation of the dye,and the maximum activity is observed for the 15%g-C3N4/LaFeO3 composite.Moreover,the photo-Fenton performance of the composites is much higher than the photocatalytic or Fenton performances.The much improved photo-Fenton activity is ascribed to the efficient separation of photogenerated electron-hole pairs due to the Z-scheme electron transfer and the synergistic effect between LaFeO3 and g-C3N4.·OH radicals were examined by PL spectroscopy using TPA as a probe molecule,clearly revealing the ·OH generation,and moreover,the ·OH yield and the dye degradation rate show a similar variation between different cases of the catalysis process.This suggested that ·OH is the dominant reactive species causing the dye degradation.(3)Ag2Cr O4/LaFeO3 composites with different weight percent of Ag2 Cr O4 were fabricated by a facile chemical precipitation method?Spherical Ag2 Cr O4 nanoparticles of 10-35 nm in size were observed by SEM and TEM and were uniformly assembled onto the surface of LaFeO3 through chemical bonding.No internal defects are visible in the monocrystalline Ag2 Cr O4/LaFeO3 composites.The photo-Fentonactivity of the samples was evaluated by degrading Rh B under simulated-sunlight irradiation.Compared to bare LaFeO3 particles,Ag2 Cr O4/LaFeO3 composites exhibit an obviously enhanced photo-Fenton activity.It is also obvious that 10%Ag2Cr O4/LaFeO3 composites exhibit most great photo-Fenton activity compared to bare LaFeO3 particles and its percentage degradation reaches 96%.The photo-Fenton activity of LaFeO3 particles is increased by 3.1 times when decorated with Ag2 Cr O4 nanoparticles.The TEM and XRD investigation reveals the good assembly of Ag2 Cr O4 particles onto LaFeO3 and the microstructure and crystal structure of the composite undergoes almost no change after four times of photo-Fenton recycling.The photo-Fenton activity enhancement of the Ag2 Cr O4/LaFeO3 heterojunction photocatalyst could be ascribed to the efficient separation of electron-hole pairs and the synergistic effect of Ag2 Cr O4 and LaFeO3.At last,the proposed photo-Fenton mechanism was discussed. |
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