Synthetically modified mixed phase inverse spinel CuFe2O4 magnetic nanoparticles: Structure, physical, and electrochemical properties for photocatalytic applications

Copper ferrite nanoparticles with crystallite sizes between 21.8 and 27.0 nm are developed by modified co-precipitation (C), two-step hydrothermal (H), and polymer-assisted sol-gel (S) methods. The synthetic conditions caused a structure and morphology variation, resulting in their optoelectrical and electrochemical properties becoming markedly different for specific photocatalytic applications. The nanoparticles are p-type semiconducting with direct optical band-gaps between 2.06 and 2.65 eV and carrier concentrations between 1017 ∼1018 cm−3. Magnetization studies demonstrate that the C-sample exhibits saturation magnetization of 32.44 emu/g nearly double as compared to that of H-sample (16.4 emu/g); however, the latter shows the highest coercivity. Impedance spectroscopy reveals faster electron transfer kinetics across the grain boundaries in the S-sample. The pellets prepared from C- and S- samples have larger dielectric constants and better oxygen ion-led conductivity owing to their larger grain size. Density Functional Theory-based calculation shows that oxygen ion conductivity plays a vital role in hole transport and thus an enhancement in the photocatalytic properties. Photocatalytic activity in the H-sample is superior with a degree of methylene blue dye degradation of 55 % in 2 h and a faster rate kinetics of 0.004 min−1 in the first hour under simulated sunlight.