Covalent grafting of redox-active sites onto MXenes with spinel ACo2O4 (A = Zn, Cu) integration for tailored interfacial charge storage in high-performance supercapacitors

Abstract

The urgent demand for efficient energy storage underscores the importance of chemically tunable nanomaterials. MXenes, with their adjustable surface groups and metallic conductivity, are ideal for supercapacitor electrodes. In this work, redox-active sulphonate groups were covalently grafted onto Ti₃C₂T_x MXene via a simple DMSO-assisted grinding method. Further enhancement was achieved by integrating 15 wt% of spinel ZnCo₂O₄ (15ZTS) and CuCo₂O₄ (15CTS), resulting in specific capacitances of 564.11 and 543.38 F g⁻¹, respectively, with excellent cycling stabilities (84.75% and 78.49% after 10 000 cycles). A symmetric supercapacitor using 15ZTS demonstrated real-world applicability by powering LEDs and retained 65.6% capacitance after 5000 cycles. The device delivered energy and power densities of 6.45 Wh kg⁻¹ and 598.48 W kg⁻¹. Theoretical studies confirmed that sulphonate functionalisation and oxide integration significantly modulate the electron environment, enhancing charge storage. This strategy offers a scalable pathway toward high-performance, redox-active MXene-based supercapacitors for next-generation energy storage applications.