Role of rare earth and coinage metals as activators for promoting the electrochemical activity of polyaniline based electrodes for water oxidation and asymmetric supercapacitor device application

The global energy crisis, environmental concerns associated with fossil fuel combustion, and the scarcity of energy resources in various regions have driven scientists and researchers to prioritize the development of efficient energy storage systems. Supercapacitors, recognized for their high energy density and extended cycling life, have emerged as vital solutions to address the challenges inherent in energy storage technologies. Furthermore, advancements in hydrogen production through electrochemical water splitting can be significantly enhanced by reducing the energy barrier for the oxygen evolution reaction (OER). This study investigates these two promising applications for high-performance electrode materials. In this research, polyaniline (PANI) was doped with coinage and rare earth metallic ions during the chemical oxidation polymerization process to modify its electronic and surface properties. The incorporation of smaller quantities of coinage metals, such as Cu and Ag, along with the rare earth element Ce, was confirmed using analytical techniques, including X-ray diffraction (XRD), Fourier transform infrared (FTIR), and UV–visible spectroscopy. Among the doped PANI materials, Ce–Cu doped PANI demonstrated exceptional efficacy for OER applications and as a component in asymmetric supercapacitor (ASC) devices. ASC devices demonstrated a specific capacitance of 881.2 F/g, energy density of 305.5 Wh/kg, a power density of 3555.1 W/kg at a same current density of 4.5 A/g. The ASC device demonstrated remarkable cycling stability across 40,000 galvanic charge-discharge cycles at a fixed current density of 4.5 A/g. Ce–Cu-doped PANI exhibited significant activity for the oxygen evolution reaction (OER) at an overpotential of 300 mV at 10 mA/cm², maintaining high durability after 30 h of operation. In addition to enhancing electrical conductivity, the incorporation of coinage and rare earth metals improved surface properties, rendering them highly suitable for energy storage applications. These results indicate that the synergistic combination of coinage and rare earth metals offers a promising approach for the development of advanced electrode materials for practical energy storage systems.