Redox-Active Nitroxide Radicals Grafted onto MXene: Boosting Energy Storage via Improved Charge Transfer and Surface Capacitance AITranslate

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DOI：https://doi.org/10.1021/acsenergylett.2c02595

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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 Ti3C2Tx 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 Ti3C2Tx 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.