Interfacial Synergy in Hierarchical FMWCNTs/α-Fe₂O₃ and Ti₃C₂T_x-MXene Electrodes for High-Performance Asymmetric...

Asymmetric supercapacitors (ASCs) possess the potential to deliver high energy and power densities. However, current systems encounter limitations arising from complex charge-storage mechanisms and from interfacial interactions between electrolyte ions and electrode materials. Herein, the electrochemical response of functionalized multiwalled carbon nanotube (FMWCNT)/α-Fe₂O₃ electrodes in an alkaline KOH electrolyte is investigated. In contrast to pristine FMWCNTs and α-Fe₂O₃, the FMWCNTs/α-Fe₂O₃ heterostructure exhibits a higher specific surface area and porosity, enhancing electrolyte diffusion and access to active sites. A high specific capacitance of 1007.3 F/g is achieved at 4 A/g, attributed to an optimized nanostructure for OH^- induced Faradaic redox reactions. These experimental enhancements are consistent with first-principles density functional theory (DFT) calculations. In addition, an ASC utilizing the FMWCNTs/α-Fe₂O₃//Ti₃C₂T_x-MXene configuration delivers a high energy density of 78.3 Wh/kg, a power density of 4072 W/kg, and excellent cycling stability, retaining 90% of the initial capacitance after 10,000 cycles. These findings establish the FMWCNTs/α-Fe₂O₃//Ti₃C₂T_x-MXene configuration as a promising platform for advanced ASCs and provide mechanistic insights into the development of scalable and efficient energy storage devices.