Optimizing La₂MnXO₆ Double Perovskite for Superior Electrochemical Efficiency in Supercapacitors

Abstract

Double perovskite oxides (POs) are effective electrode materials for supercapacitors (SCs). Nevertheless, adapting their unique architectures to boost the electrochemical performance remains tricky. Herein, we present exceptional La₂MnXO₆ (X = Co, Fe) double perovskites as SC electrode materials. The sol–gel method has prepared La₂MnCoO₆ (LMCO) and La₂MnFeO₆ (LMFO) nanorods. XRD revealed that LMCO and LMFO have monoclinic crystal structures with lattice constants of a = 5.517 Å, b = 5.528 Å, c = 7.805 Å, β = 89.926°, and a = 5.549 Å, b = 5.557 Å, c = 7.783 Å, β = 89.931°, respectively. Scanning electron microscopy indicated the existence of uniformly distributed nanorods. The bandgap using Tauc's plot was determined as 1.38 and 1.24 eV for La₂MnCoO₆ and La₂MnFeO₆, respectively. Fourier-transform infrared spectroscopy further characterized the prepared LMCO and LMFO nanorods. X-ray photoelectron spectroscopy investigation confirmed the existence of La³⁺, Mn³⁺, Fe³⁺, O²⁻, and La³⁺, Mn³⁺, Co³⁺, O²⁻ ions on the surface of La₂MnFeO₆ and La₂MnFeO₆, respectively. The specific capacitance achieved was 333.86 and 880.5 F/g @ 2.5 A/g for La₂MnCoO₆ and La₂MnFeO₆, respectively, using 1 M KOH electrolyte. La₂MnFeO₆ demonstrated excellent energy and power density of 30.5 Wh/kg and 625 W/kg. The asymmetric CV curve shape proved that we have battery-type SC behavior due to the indication of redox reactions. Furthermore, Dunn's technique evaluated the percentage contribution of capacitive and diffusion behavior. Our strategy using LMCO and LMFO nanorods material improved specific capacitance activity and significantly offered a facile guideline for targeting double perovskite electrodes for SC applications.