In-situ magnetic nanocomposite of fluorite MO2 and spinel M3O4 (where M = Mn, Fe, Co, Ni and Ce) for photocatalytic application.

The fluorite structured CeO2 is a well-known material for catalysis, sensors, fuel cells, and environmental remediation application due to rapid Ce4+/Ce3+ cycling. Similarly, the recently reported high entropy oxides (HEOs) have tailorable bandgaps, improved charge separation, and multiple redox-active sites, which make them an efficient catalyst for pollutant degradation. Herein, we report the catalytic property of in-situ nanocomposite of fluorite MO2 and spinel structured high entropy oxide of M3O4 (where M = Mn, Fe, Co, Ni and Ce). The composite was able to degrade around 92% of the methylene blue (MB) dye in 60 min during the photo-Fenton reaction. Further, the mass spectroscopy (MS) study of the solution obtained after complete degradation (in 90 min) of MB justified its total mineralisation. The magnetization value of ~ 25 emu/g of the composite endorses its ability for easy recovery and recycling. The structural and morphological studies via x-ray diffraction and transmission electron microscopy indicate the existence of both CeO2 and M3O4 (spinel structure) phases. The valences of the respective cations were confirmed from x-ray photoelectron spectroscopy.