Pd-Doped RuO2: A Promising Electrode Material with Battery–Supercapacitor Hybrid Characteristics

Supercapacitors have emerged as promising energy storage devices due to their high power density, rapid charging/discharging rates, and long cycle life. Ruthenium dioxide (RuO₂) is a promising material for supercapacitor electrodes due to its excellent electrical conductivity and pseudocapacitive behavior. Here, we synthesize Ru_1–xPd_xO₂ (x = 0, 0.05, 0.10, and 0.17) by a solid-state route, expecting to alter the electronic structure and specific capacitance with Pd doping. The X-ray diffraction (XRD) analysis suggests that all prepared samples are formed in the desired composition, showing that the crystallite size increases successively with increasing Pd concentration. Cyclic voltammetry (CV) measurements demonstrate that the systematic substitution of 17% Pd in RuO₂ contributes to enhancing specific capacitance by ∼15 times (∼1163 F/g) in comparison to parent RuO₂ (∼79 F/g), indicating its superior charge storage ability. Further, the decay in specific capacitance with increasing scan rate is only 5% (x = 0.17) in comparison to undoped RuO₂, indicating the higher stability of the electrode. The CV of Ru_1–xPd_xO₂ (x = 0.17) exhibits both Faradaic and capacitive electrochemical processes at the electrode/electrolyte interface, suggesting hybrid battery–supercapacitor characteristics. Ru_1–xPd_xO₂ (x = 0.17) represents a promising electrode material for hybrid battery–supercapacitors, offering synergistic enhancements in specific capacitance and stability.