Development of Graphitic Carbon Nitride-Encapsulated SrFe₂O₄ Spinel Nanocomposite Electrode for Enhancing Supercapacitor and Oxygen Evolution Applications

In the past few years, there has been a notable upswing in the excitement surrounding bifunctional materials, primarily due to their versatility in accommodating energy storage and conversion needs. One class of materials that garnered considerable attention is strontium ferrite nanoparticles (NPs), which are known for their remarkable electrochemical properties stemming from their exceptional physical and chemical characteristics. In this study, we have synthesized a novel, cost-effective, and highly efficient composite electrode designed for dual functionality in supercapacitor (SC) and oxygen evolution reaction (OER) applications in alkaline environments. Herein, we prepared SrFe₂O₄@g-C₃N₄ composite through a coprecipitation and pyrolysis method, resulting in featuring a porous g-C₃N₄ matrix and strontium (Sr) spinel structure. The composite materials were thoroughly characterized using techniques such as powder X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy. The SrFe₂O₄@g-C₃N₄ electrode exhibited outstanding pseudocapacitive behavior and delivered a specific capacitance of 1055 F/g at a current density of 1 A/g. Remarkably, it displayed a capacitance retention of 93% even after 5000 galvanostatic charge–discharge (GCD) cycles. Furthermore, in comparative assessments with bare SrFe₂O₄ or g-C₃N₄ electrodes, the SrFe₂O₄@g-C₃N₄ composite electrode displayed superior and stable electrocatalytic performance. It required minimal overpotentials (only 170 mV) to achieve a current density of 10 mA cm^–2 during the OER. These results emphasize the substantial potential of Sr-based nanocomposites as auspicious materials for applications in supercapacitors and as stable electrocatalysts.