Fe doped ZnO nanomaterials for energy storage applications as high-capacitance supercapacitor electrodes

Enhancing the performance of electrode materials is essential for developing high-capacitance supercapacitors, and transition-metal-doped metal oxides have shown particular promise in this regard. In this work, Fe-doped ZnO nanostructures were synthesized using a sonochemical method and systematically examined through XRD, SEM, TEM, XPS and UV-vis analyses to verify Fe incorporation and the resulting changes in crystallinity, morphology and optical behaviour. The structural modifications induced by Fe were evident in the electrochemical response, with the optimized ZnO-Fe sample delivering a specific capacitance of 11.4 F g^-1 at 0.1 A g^-1 in the two-electrode system and 462 F g^-1 in the three-electrode system, both measured in 3 M KOH electrolyte. A CR2032 coin cell assembled with this material achieved an energy density of 1.6 Wh kg^-1 and a power density of 2890.93 W kg^-1, demonstrating an effective balance between energy storage and power output. These findings highlight the suitability of Fe-doped ZnO as a tunable electrode material and support its further exploration in advanced supercapacitor systems.