Activity enhancement pathways in LaFeO@TiO heterojunction photocatalysts for visible and solar light driven degradation of myclobutanil pesticide in water.

LaFeO@TiO heterojunction composites with a core-shell porous structure and LaFeO contents in the 2.5-25 wt.% range have been synthesized via consecutive sol-gel syntheses and tested for the photocatalytic oxidation of the myclobutanil pesticide in water under solar light and pure visible light. Whatever the light spectrum, the kinetic rate constants for both myclobutanil degradation and TOC conversion exhibited a volcano-like profile with increasing the narrow band-gap (2.1 eV) LaFeO content, the optimum composite strongly overperforming both single phases, with full myclobutanil mineralization achieved in 240 min in the best case. The light spectrum influenced the optimum LaFeO content in the composite, being observed at 5 wt.% and 12.5 wt.% under solar and visible light, respectively. This has been attributed to the existence of different light-mediated reaction mechanisms. The optimum LaFeO/TiO composite photocatalyst was active and stable after several runs under solar light with leached iron concentration below 0.1 mg/L in solution.