Eco-friendly clay-based electrodes: Lanthanum oxide-modified and K/Mn co-doped montmorillonite for advanced supercapacitors

Abstract

In this study, a hybrid electrode material based on lanthanum oxide-modified montmorillonite (Mont@La2O3) and its potassium-manganese co-doped derivative (K/Mn-Mont@La2O3) was successfully synthesized through sequential calcination and hydrothermal routes. Comprehensive structural and surface characterizations, including XRD, FTIR-ATR, SEM, TEM, XPS, and BET analyses, were performed to elucidate the morphological and chemical transformations induced by doping. XRD results confirmed the successful incorporation of La2O3 and MnO2 phases into the montmorillonite framework while retaining the layered silicate structure. XPS analysis further verified the coexistence of La3+ and Mn4+ species and a notable increase in oxygen-rich surface functionalities. Electrochemical evaluations were conducted using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) in a 1 M KOH electrolyte. The K/ Mn-Mont@La2O3 electrode delivered a high specific capacitance of 411.42 F g- 1 at a current density of 0.1 A g- 1. Furthermore, EIS measurements revealed a drastic reduction in charge transfer resistance from 740.2 Omega to 27.2 Omega, indicating markedly enhanced electrical conductivity and ion transport. The synergistic interaction between La2O3 and MnO2 contributes to improved redox activity and charge storage kinetics. Overall, this work introduces a cost-effective, eco-friendly, and scalable route for designing high-performance clay-based electrode materials, offering significant potential for next-generation supercapacitor applications.