The potential window of aqueous supercapacitors is limited by the theoretical value (≈1.23 V) and is usually lower than ≈1 V, which hinders further improvements for energy density. Here, a simple and scalable method is developed to fabricate unique graphene quantum dot (GQD)/MnO₂ heterostructural electrodes to extend the potential window to 0–1.3 V for high‐performance aqueous supercapacitor. The GQD/MnO₂ heterostructural electrode is fabricated by GQDs in situ formed on the surface of MnO₂ nanosheet arrays with good interface bonding by the formation of MnOC bonds. Further, it is interesting to find that the potential window can be extended to 1.3 V by a potential drop in the built‐in electric field of the GQD/MnO₂ heterostructural region. Additionally, the specific capacitance up to 1170 F g⁻¹ at a scan rate of 5 mV s⁻¹ (1094 F g⁻¹ at 0–1 V) and cycle performance (92.7%@10 000 cycles) between 0 and 1.3 V are observed. A 2.3 V aqueous GQD/MnO₂‐3//nitrogen‐doped graphene ASC is assembled, which exhibits the high energy density of 118 Wh kg⁻¹ at the power density of 923 W kg⁻¹. This work opens new opportunities for developing high‐voltage aqueous supercapacitors using in situ formed heterostructures to further increase energy density.

中文翻译：

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异质结构石墨烯量子点/MnO2纳米片用于高性能超级电容器的高电位窗口电极

水系超级电容器的电位窗口受到理论值（约1.23 V）的限制，通常低于约1 V，这阻碍了能量密度的进一步提高。在此，开发了一种简单且可扩展的方法来制造独特的石墨烯量子点（GQD）/MnO ₂异质结构电极，将高性能水系超级电容器的电势窗口扩展到0-1.3 V。GQD/MnO _{2异质结构电极是通过在MnO 2}纳米片阵列表面原位形成GQD来制备的，通过形成Mn  O  C键，具有良好的界面结合。_{此外，有趣的是发现通过 GQD/MnO 2}异质结构区域内建电场的电势下降，电势窗口可以扩展到 1.3 V。此外，扫描速率为 5 mV s ^-1时比电容高达 1170 F g ^-1 （ 0–1 V 时为1094 F g ^-1 ），循环性能（92.7%@10 000 次循环）在 0 至 1.3 V 之间被观察到。组装了2.3 V水基GQD/MnO _{2 ‐3//氮掺杂石墨烯ASC，其在923 W kg} ^-1的功率密度下表现出118 Wh kg ^-1的高能量密度。这项工作为利用原位形成的异质结构开发高压水系超级电容器以进一步提高能量密度开辟了新的机会。