Palladium-Engineered MgFeO₃ Perovskite Nanostructures as Advanced Electrode Materials for High-Performance Asymmetric Supercapacitors

Abstract

Capacitive energy storage offers rapid charging, long operational lifespan, and high power density. This work introduces a simple yet effective palladium (Pd)-doping strategy to enhance the electrochemical performance of perovskite-type magnesium ferrite (MgFeO₃) nanostructures (Mg₁₋ₓPdₓFeO₃, PMFs), where 'x' varies from 0 to 0.20. Pd incorporation modifies the crystallite size and Mg/Fe ratio, tuning the physical, chemical, and electrochemical properties. Electrochemical tests in a three-electrode system using 6.0 M KOH reveal a marked enhancement in specific capacitance (SC) after doping: at x = 0.15 (PMF-C), the SC increases from 581 to 820 F g⁻¹ at 2 mA cm⁻². The assembled PMF-C//Bi₂O₃ asymmetric supercapacitor delivers an energy density of 88.70 Wh kg⁻¹ at 1500 W kg⁻¹, with an SC of 283.9 F g⁻¹ and 91.66% retention after 20,000 cycles. A "CNED" display of 42 LEDs reaches full brightness using a twin-cell assembly, highlighting the potential of Pd-doped perovskite ferrites for space, agricultural, medical, and robotic technologies. Kinetic analysis confirms that PMF-C possesses the highest electrochemically active surface area (0.55 cm²) and a capacitive-dominated hybrid charge-storage mechanism, which, together with its low charge-transfer resistance, account for its superior rate capability.