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Nitroxide radicals have fast and reversible redox reactions and high electron transfer rates, while the instability in electrolytes and low conductivity restrict their applications on electrodes. Here, we employ two-dimensional MXene Ti 3 C 2 T x as a conductive film-forming agent for 4-amino-TEMPO (TEMPO = 2,2,6,6-tetramethylpiperidine-1-oxyl) to prepare a freestanding and flexible electrode. Pendant nitroxide radicals experience two-electron storage through reversible redox reactions and realize synergistically boosted charge storage with redox-active Ti 3 C 2 T x nanosheets. A systematic electrochemical investigation demonstrates that nitroxide radicals greatly contribute to the surface capacitance of the hybrid electrode, which significantly improves its diffusion-capacitive dual-model energy storage and cycling stability. Further, the assembled symmetric supercapacitor achieves a high energy density of 60.3 Wh kg –1 and the all-in-one asymmetric supercapacitor shows a wide potential window of 1.8 V, demonstrating great promise in energy storage devices.
Chen et al. (Tue,) studied this question.