Bifunctional supercapacitor electrode based on gamma-radiation-engineered carbon/cobalt nanoarchitecture anchored on carbon nanofibers

Carbon-metal composite electrodes have emerged as promising candidates by synergistically combining the high-power density and structural stability of carbon frameworks with metal-based pseudocapacitance. However, their practical implementation is hindered by uncontrollable microstructural evolution during conventional thermal annealing processing, which leads to agglomeration and insufficient interfacial coupling. Furthermore, these composites often operate within a narrow voltage window due to the parasitic reactions of metal species. Herein, the gamma irradiation strategy was introduced to engineer uniform carbon/cobalt (C/Co) nanoarchitectures on carbon nanofibers (CNFs) for supercapacitors with high electrochemical performance. Unlike the conventional annealing process, gamma irradiation produces a uniformly distributed C/Co nanoarchitecture induced by local thermal spikes, owing to its high energy and strong penetration. Moreover, gamma irradiation provides additional effects, including healing of the sp² carbon network and electronic coupling of Co–N–C. Electrochemical analysis of the gamma-irradiated electrode showed that G-Co/CNF_L (50 kGy) and G-Co/CNF_H (200 kGy) exhibit the highest capacitance of 435 F g⁻¹ and 84 F g⁻¹ at 1 A g⁻¹ as the cathode and anode, respectively. The asymmetric supercapacitor assembled using two different electrode materials (G-Co/CNF_H//G-Co/CNF_L) achieves 46.3 Wh kg⁻¹ at 1011 W kg⁻¹ with 97% retention after 20,000 cycles, demonstrating that gamma irradiation is a powerful tool for tailoring high-performance carbon-metal nanoarchitectures.