Tuning the redox chemistry of CeO2 through Ag doping for supercapacitor electrodes

The development of advanced electrode materials with tailored defect structures is essential for enhancing supercapacitor performance. In this study, Ag doping is used to engineer oxygen vacancies in CeO 2 , significantly improving its redox activity. Ag-doped CeO 2 nanostructures are synthesized via a simple, cost-effective coprecipitation method. Structural analysis using XRD, Raman, and FTIR confirms the formation of cubic CeO 2 . XPS reveals that Ag incorporation stabilizes Ce 3 + ions, maintaining charge neutrality and increasing oxygen vacancies. SEM shows that pristine CeO 2 forms sphere-like structures, while Ag doping alters the structure to nanogranules, with TEM confirming the granule morphology. The aggregation of ceria granules into spheres is influenced by Ag substitution. The charge storage properties of the electrodes are evaluated using a three-electrode system, with Faradaic reaction-based energy storage observed from CV, GCD, and AC impedance analyses. The Ag-doped CeO 2 electrodes exhibit a maximum specific capacitance of 551 F g –1 at 2 A g –1 , 2.1 times higher than pristine CeO 2 (270 F g –1 ). Ag doping also reduces charge transfer resistance to 1.6 Ω, a 30.8% decrease compared to pristine CeO 2 (5.2 Ω). An asymmetric supercapacitor cell delivers a maximum specific energy of 29 W h kg –1 at 277 W kg –1 . This strategic modification of Ce 4+ via Ag doping not only stabilizes Ce 3+ but also introduces abundant active sites, making Ag-doped CeO 2 a promising candidate for next-generation energy storage devices.