Redox flow batteries (RFBs) are a promising technology for the storage of intermittent renewable energy. Graphite and carbon felts electrodes are commonly used in RFBs as they typically exhibit good conductivity, high liquid permeability, high surface area and are relatively inexpensive. The electrochemical performance of carbon felts is commonly tested by calculating the energy efficiency for charge-discharge cycles of electrochemical cells containing the felt electrodes. This method whilst useful does not provide a direct measure of the kinetics of the redox reactions at the electrode surface. Furthermore, the standard electrochemical methods (e.g. cyclic voltammetry) commonly used to determine the electron transfer kinetics cannot be easily applied to carbon felt electrodes due to the complex mass transport behaviour within the porous felts. In this work we have shown that kinetics at carbon felts can be determined by performing cyclic voltammetry on single carbon fibre electrodes extracted from the carbon felt. This approach avoids the complex mass transport behaviour while also providing a method to determine the distribution of rate constants within a carbon felt electrode. By combining this measured rate constant distribution with the void size distribution of the carbon felt, the cyclic voltammetry of carbon felt electrodes can be successfully simulated over a wide range of sweep rates. Importantly, this approach highlights the necessity of accounting for the rate constant distribution within carbon felt electrodes.

氧化还原液流电池（RFB）是用于存储间歇性可再生能源的有前途的技术。石墨和碳毡电极通常用于RFB，因为它们通常表现出良好的导电性，高的液体渗透性，高的表面积并且相对便宜。通常通过计算包含毡电极的电化学电池的充放电循环的能量效率来测试碳毡的电化学性能。该方法虽然有用，但不能直接测量电极表面氧化还原反应的动力学。此外，由于多孔毡内复杂的传质行为，通常用于确定电子转移动力学的标准电化学方法（例如循环伏安法）不易应用于碳毡电极。在这项工作中，我们表明可以通过对从碳毡中提取的单个碳纤维电极进行循环伏安法来测定碳毡的动力学。这种方法避免了复杂的传质行为，同时还提供了一种确定碳毡电极内速率常数分布的方法。通过将这种测得的速率常数分布与碳毡的空隙尺寸分布结合起来，可以在很宽的扫描速率范围内成功地模拟碳毡电极的循环伏安法。重要的是，这种方法强调了考虑碳毡电极内速率常数分布的必要性。