The impact of Sm substitution on structural and optical properties of LaFeO₃: their application as a photocatalyst for the degradation of methylene blue under visible light irradiation

Abstract

The objective of the present study is to enhance the photocatalytic activity of LaFeO3 by inserting Sm ions on the La site for the degradation of methylene blue. We employed citric sol-gel techniques to produce ultrafine powders of the La1-xSmxFeO3 (0.0 ≤ x ≤ 0.5) nanoperovskite samples. All samples confirmed the presence of a pure Pbnm orthorhombic phase structure. The decrease of lattice constants, crystallite sizes and cell volumes, and increase in microstrains suggest a deformation of the structure due to the addition of Sm ion on the La site of the La1-xSmxFeO3. The images of HR-TEM and FE-SEM for all samples revealed a homogeneous distribution of almost spherical nanoparticles, with decreasing average particle sizes ranging from 49.95 ± 3.12 to 34.28 ± 4.38 nm, as Sm ratios increases from 0.0 to 0.5%. The spectra of FTIR confirmed the formation of a Lax-1SmxFeO3 perovskite phase by the appearance of lower frequency bands Fe–O-Fe and La-O-La at ~ 400 cm-1 and a higher absorption band Fe -O and La -O at ~ 564 cm-1. The Raman spectra were employed to investigate the formation of phonon modes of La1-xSmxFeO3. Diffused reflectance spectroscopy (DRS) demonstrated the decrease of energy gap (Eg) values from 2.38 to 1.86 eV and the increase in Sm content from 0.0 to 0.5%. Since these Eg values fall within the visible light region, the photocatalytic activity of La1-xSmxFeO3 samples demonstrated a gradual increase in the degradation ratio of MB from 31.7 to 73.2% with increasing Sm content from 0.0 to 0.5%, respectively, under visible light illumination.