Synthesis and performance evaluation of S-scheme heterostructured LaFeO3/TiO2 photocatalyst for the efficient degradation of thiamethoxam.

The application of perovskite lanthanum ferrite (LaFeO3) as a photocatalyst has shown significant potential in the removal of persistent organic and inorganic contaminants. In the present research, LaFeO3 and various composites consisting of LaFeO3 and TiO2 were prepared. The photocatalytic efficiency of the produced catalysts was assessed by measuring their effectiveness in degrading thiamethoxam, a pesticide belonging to the second generation of neonicotinoids. Experimental investigations were carried out to examine the impact of various factors on the degradation process, including variables like concentration of thiamethoxam, catalyst amount, and pH level. The produced catalysts were characterized by various techniques, including field emission scanning electron microscopy (FESEM), Brunauer-Emmett-Teller (BET) analysis, X-ray diffraction (XRD), ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS), photoluminescence (PL), and X-ray photoelectron spectroscopy (XPS). The highest degradation rates were observed when using the synthesized catalyst, 1% LaFeO3/TiO2 (LFTO1), under both UV-C and direct sunlight conditions. This performance outperformed TiO2 and bare LaFeO3. When exposed to ultraviolet (UV-C) radiation at an intensity of 15 W m-2 and under neutral pH conditions, LFTO1 achieved approximately 97% degradation, while under direct sunlight, the LFTO1 photocatalyst exhibited a degradation rate of 79% within a 120-min reaction period. The enhanced activity of LFTO1 could be attributed to its increased surface area, reduced bandgap, and lower electron-hole recombination. The investigation of reaction kinetics showed that the degradation of thiamethoxam followed a pseudo-first-order rate law. Furthermore, LFTO1 can be employed up to 5 times without experiencing any loss in its catalytic activity, thus confirming its long-term utility.