Enhanced Electrochemical Performance of Highly Porous <scp>CeO₂</scp>‐Doped Zr Nanoparticles for Supercapacitor Applications

The aim of this work was to develop an ultrasonic-assisted synthesis method for the fabrication of CeO₂-doped Zr nanoparticles that would improve the performance of supercapacitor electrodes. This method, which eliminates the need for high-temperature calcination, involves embedding CeO₂ into Zr nanoparticles through 1 hr (CeO₂-Zr-1) and 2 hrs (CeO₂-Zr-2) of ultrasonic irradiation, resulting in the formation of nanostructures with significant improvements in their electrochemical properties. Through physicochemical analysis, we observed that the CeO₂-doped Zr nanoparticles, particularly those treated for 2 hrs (CeO₂-Zr-2), exhibit superior crystalline phase purity, optimal chemical surface composition, minimal agglomeration with particle sizes below 50 nm, and an impressive average surface area of 178 m²/g. Compared to the 1 hr irradiation samples (CeO₂-Zr-1) and undoped CeO₂ nanoparticles, the (CeO₂-Zr-2) electrodes demonstrated a remarkable capacitance of 198 Fg^-1 at a current density of 1 A/g while maintaining ~94.9% of their capacity after 3750 cycles. This indicates not only good reversibility but also exceptional stability. In (CeO₂-Zr-2) samples, the nanospherical structure achieved through ultrasonic synthesis is responsible for the enhanced capacitive behavior and stability, along with the synergistic effects caused by Zr doping, which improves the CeO₂ nanoparticle conductivity to a significant extent. Surface areas of the electrodes are larger due to the combination of these two materials, which contribute to their superior performance.