Influence of Fe and Cu Co-Doping on Structural, Magnetic and Electrochemical Properties of CeO₂ Nanoparticles

The nanoparticles of CeO₂, Ce_0.98Fe_0.02O₂, and Ce_0.78Fe_0.02Cu_0.20O₂ were synthesized using the co-precipitation-synthesis technique. The effect of co-doping of Fe and Cu on structural, optical, and magnetic properties as well as specific capacitance have been studied using X-ray diffraction (XRD), scanning-electron microscopy (SEM), UV-visible spectroscopy, Raman spectroscopy, dc magnetization, and electrochemical measurements at room temperature. The results of the XRD analysis infer that all the samples have a single-phase nature and exclude the formation of any extra phase. Particle size has been found to reduce as a result of doping and co-doping. The smallest particle size was obtained to be 5.59 nm for Ce_0.78Fe_0.02Cu_0.20O₂. The particles show a spherical-shape morphology. Raman active modes, corresponding to CeO₂, were observed in the Raman spectra, with noticeable shifting with doping and co-doping indicating the presence of defect states. The bandgap, calculated using UV-Vis spectroscopy, showed relatively low bandgap energy (1.7 eV). The dc magnetization results indicate the enhancement of the magnetic moment in the samples, with doping and co-doping. The highest value of saturation magnetization (1.3 × 10^-2 emu/g) has been found for Ce_0.78Fe_0.02Cu_0.20O₂ nanoparticles. The electrochemical behavior studied using cyclic-voltammetry (CV) measurements showed that the Ce_0.98Fe_0.02O₂ electrode exhibits superior-specific capacitance (~532 F g^-1) along with capacitance retention of ~94% for 1000 cycles.