New methods for interconversion of electrical and chemical energy are crucial to addressing emerging challenges in renewable energy storage and conversion. Dissolved redox mediators provide an effective means to transport electrons (and protons) between an electrode and catalysts that are not in direct physical contact with an electrode. Mediators are widely implemented in biofuel cells, but such devices typically exhibit low power densities. Here, we report the development of a tetrasubstituted quinone mediator that exhibits excellent stability under strongly acidic conditions and supports electrochemical reduction of O₂ at an off-electrode heterogeneous cobalt catalyst contained within a packed-bed reactor. Efficient oxidation of the hydroquinone by O₂ in the reactor provides the basis for mediator regeneration, and an integrated “flow-cathode” fuel cell system supports high power densities. These results establish the combination of organic mediators with off-electrode heterogeneous catalysts as a versatile platform for development of new electrode-driven chemical redox transformations.

电能和化学能相互转换的新方法对于应对可再生能源存储和转换中出现的新挑战至关重要。溶解的氧化还原介体提供了一种在电极与未与电极直接物理接触的催化剂之间传输电子（和质子）的有效手段。介体在生物燃料电池中得到了广泛的实现，但是这种设备通常表现出低功率密度。在这里，我们报告了四取代醌介体的开发，该介体在强酸性条件下表现出出色的稳定性，并支持在填充床反应器内的非电极多相钴催化剂上电化学还原O ₂。O ₂有效氧化对苯二酚反应堆中的燃料为介体再生提供了基础，而集成的“液流阴极”燃料电池系统支持高功率密度。这些结果建立了有机介体与离电极非均相催化剂的结合，作为开发新的电极驱动的化学氧化还原转化的通用平台。