Graphenated carbon nanotube (G-CNT) cotton/MoSe2 electrodes engineered by gamma irradiation for high areal capacitance supercapacitors

Defect engineering of carbon architectures has emerged as an effective strategy to improve interfacial charge storage in carbon-based supercapacitor electrodes. However, achieving controlled defect generation without damaging the conductive framework remains challenging. In this work, gamma-irradiation was used to modulate the surface structure of graphenated carbon nanotube (G-CNT) cotton before MoSe2 growth to develop high-performance flexible supercapacitor electrodes with improved electrode–electrolyte interaction and charge transport. A systematic irradiation treatment (0, 10, 20, 30, 40, 50 kGy) was applied to the three-dimensional G-CNT framework, followed by Radio-Frequency (RF) magnetron sputtering of MoSe2. A moderate dose of 30 kGy produced an optimum irradiation-induced structural state, which promoted uniform MoSe2 anchoring, enhanced electrolyte accessibility, and improved charge-transfer kinetics. The optimized D30–M30 electrode delivered an areal capacitance of 236.7 mF cm−2 from CV and 189.4 mF cm−2 from GCD, together with a GCD-derived areal energy density of 9.47 μWh cm−2 at a power density of approximately 300.13 μW cm−2. In contrast, excessive irradiation (≥40 kGy) led to structural degradation and diminished electrochemical performance. An asymmetric flexible supercapacitor device constructed using D30–M30 and rGO/G-CNT electrodes operated within a 0–1.0 V window and achieved an areal energy density of 4.44 μWh cm−2 at a power density of 1000 μW cm−2, while retaining 97% of its initial capacitance after 5000 cycles with nearly 100% coulombic efficiency. In addition, the flexible device largely preserved its CV and GCD responses under 90° bending, confirming its mechanical stability for flexible supercapacitor applications. This gamma- irradiation-induced defect engineering of the G-CNT framework facilitated uniform MoSe2 integration, leading to enhanced interfacial charge transport and improved electrochemical durability in MoSe2/G-CNT electrodes.