Ultrasonic-assisted synthesis of LaFeO3/CeO2 heterojunction for enhancing the photocatalytic degradation of organic pollutants

Abstract

Novel type I LaFeO3/CeO2 heterostructures were prepared via a facile ultrasonic synthetic process to induce boosted charge carrier separation and high photocatalytic activity. The formed nanocomposites were characterized by XRD, DRS, XPS, SEM, EDX, HRTEM, PL, and N2 adsorption-desorption analyses, which indicated that the LaFeO3/CeO2 heterojunction was successfully synthesized. DRS analysis showed that a suitable band gap was crucial for enhancing photocatalytic activity. The high surface area of LFO/Ce = 3:7 (65.292 m2/g) relative to LaFeO3 (19.934 m2/g) and CeO2 (47.876 m2/g) provided more active sites, which led to a further enhancement in photocatalytic activity. Moreover, the coupling of LaFeO3 and CeO2 improved the lifetime of charge carriers, as confirmed by the photoelectrochemical analysis. The performance of these LaFeO3/CeO2 composites for the photocatalytic degradation of organic pollutants under visible light was examined. Notably, the sample LFO/Ce = 3:7 displayed the highest photocatalytic activity for methylene blue (MB), rhodamine B (RhB), and tetracycline (TC) degradation. The removal rates of MB, RhB, and TC by LFO/Ce = 3:7 were respectively 2.1 and 2.7, 1.1 and 1.6, and 2.3 and 1.9 times higher than those of pure LaFeO3 and CeO2 within the same degradation time. The TOC analysis of the degraded product verified the high mineralization (68%) of MB by LFO/Ce = 3:7. Scavenging experiments and ESR studies indicated that h+ and •OH were the main active species during the photocatalytic degradation. The LaFeO3/CeO2 composites with type I heterostructures facilitated the separation of photogenerated e-h+ pairs and prevented their recombination. Consequently, various active species (h+, •OH, and •O2−) were generated. Therefore, these efficient LaFeO3/CeO2 heterostructures show great promise as effective photocatalysts for complex environmental wastewater purification.