Synthesis and characterization of a nanocomposite of an iridium-based complex with mesoporous g-C3N4 and its application as a supercapacitor

Abstract

The depletion of nonrenewable energy sources and the consequences on the environment brought about by the increase in global energy usage have made energy storage techniques an exceptional option for energy supply. Supercapacitors stand out among them due to their incredible attributes as an electrical energy storage device. Among the three types of materials used in supercapacitors, namely, carbon-based materials, conducting polymers, and transition metal oxides/hydroxides, metal oxides, especially toxic and high-cost oxides, such as RuO₂ and IrO₂, encounter difficulties that restrict their application in supercapacitors, which can be overcome via the integration of carbon-based materials that are porous and stable. In this study, we prepared an iridium-based complex and its composite with mesoporous g-C₃N₄, determined their structures, and compared their electrochemical behavior. The structure and morphology of the as-prepared materials were determined by energy-dispersive X-ray (EDX) analysis, X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) analysis, and Fourier transform infrared (FTIR) spectroscopy. Electrochemical measurements and testing indicated the notable influence of mesoporous g-C₃N₄, improving the specific capacitance from 574 F g⁻¹ to 2302 F g⁻¹ and energy density from 11.8 Wh kg⁻¹ to 47.3 Wh kg⁻¹ at a current density of 2 A g⁻¹ in [4,4′-dmbipy·H]₂[IrCl₆] and [4,4′-dmbipy·H]₂[IrCl₆]@mesoporous g-C₃N₄, respectively. Additionally, [4,4′-dmbipy·H]₂[IrCl₆] showed a 99.27% Coulombic efficiency after 5000 cycles at a current density of 8 A g⁻¹, which increased to a notable 100.46% Coulombic efficiency after 5000 cycles at a high current density of 20 A g⁻¹.