Abstract While carbons are common electrode materials for electrochemical capacitors (ECs) owing to their abundance, affordability, and environmental compatibility, graphene is particularly desirable due to its high electronic conductivity and high surface area for double-layer charging. However, very little is known about graphene's self-discharge (SD) – the spontaneous potential loss that occurs when a device rests idle. Knowledge of SD mechanisms is key because this process limits EC applications and reliability. Herein, we show carbon oxidation and charge redistribution – charge movement to eliminate potential gradients within a material – are key SD mechanisms for reduced graphene oxide (rGO) in acidic-aqueous electrolytes. Differentiating between these phenomena proves challenging; both processes present similar SD profiles. To address this, a novel experimental protocol is developed which resets CR to hold this process constant; when applied, this protocol separates CR contributions from carbon oxidation. We thus can identify charge redistribution as the primary SD mechanism, with a smaller but important contribution (17% of original SD) from carbon oxidation. From this work, it is clear that rGO SD can be significantly reduced by oxidizing (achieved here by CV cycling) and by more fully charging the rGO material (achieved through repeated charge/SD cycles).

中文翻译：

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作为还原氧化石墨烯电化学电容器电极中自放电机制的碳氧化和电荷重新分布的识别和隔离

摘要 虽然碳由于其丰富性、经济性和环境兼容性而成为电化学电容器 (ECs) 的常用电极材料，但石墨烯由于其高电导率和高表面积用于双层充电而特别受欢迎。然而，人们对石墨烯的自放电 (SD) 知之甚少，即设备闲置时发生的自发电位损失。SD 机制的知识是关键，因为这个过程限制了 EC 的应用和可靠性。在此，我们展示了碳氧化和电荷重新分布——电荷移动以消除材料内的电位梯度——是酸性水电解质中还原氧化石墨烯 (rGO) 的关键 SD 机制。区分这些现象证明是具有挑战性的。两个过程都呈现相似的 SD 配置文件。为了解决这个问题，开发了一种新的实验方案，它可以重置 CR 以保持该过程不变；应用时，该协议将 CR 贡献与碳氧化分开。因此，我们可以将电荷再分配确定为主要的 SD 机制，碳氧化的贡献较小但很重要（原始 SD 的 17%）。从这项工作中，很明显，rGO SD 可以通过氧化（这里通过 CV 循环实现）和通过更充分地充电 rGO 材料（通过重复充电/SD 循环实现）来显着降低。来自碳氧化的较小但重要的贡献（原始 SD 的 17%）。从这项工作中，很明显，rGO SD 可以通过氧化（这里通过 CV 循环实现）和通过更充分地充电 rGO 材料（通过重复充电/SD 循环实现）来显着降低。来自碳氧化的较小但重要的贡献（原始 SD 的 17%）。从这项工作中，很明显，rGO SD 可以通过氧化（这里通过 CV 循环实现）和通过更充分地充电 rGO 材料（通过重复充电/SD 循环实现）来显着降低。