Supercapacitor performance, electronic structure and ferromagnetic properties of TM and RE cations of co-doped (Fe, Yb) CeO2 nanoparticles

Abstract

The undoped CeO₂ and Ce_1-x-yYb_xFe_yO₂ nanoparticles (NPs) while maintaining a consistent doping concentration of both cations. The effects of Yb-Fe co-doping on the overall structural, optical, electrical, and magnetic characteristics of CeO₂ NPs were investigated. The findings of XRD patterns demonstrated the FCC structure of CeO₂ with improved crystallinity. The binary doping in CeO₂ resulted in decreased crystalline size as measured by XRD and TEM analysis. By using EDX analysis, the elemental and compositional features were addressed and absorption spectra revealed red shifting. The luminescence emissions were identified as warm yellow light with CCT below 4000 K for indoor applications. The XPS observations for the core levels Ce 3d, O 1s, Yb 4d, and Fe 2p revealed the valence states of Ce with 3+ and 4+, Yb, Fe with 3+, O with 2- and the formation of oxygen vacancies. The weak ferromagnetic behaviour of the samples was attributed to the mechanisms of bound magnetic polarons and the formation of complexes promoting F⁺ centers. At a scan rate of 5 mV/s in 2 M KOH electrolyte solution, the Ce_0.91Y_0.03F_0.06O₂ sample demonstrated the highest supercapacitance of 89.66 F/g, indicating the best cycle stability 109.27 % after 1000 cycles. The power density and energy density of this sample were determined to be 325 W/kg and 2.80 Wh/kg, respectively.