Advances in bespoke diagnostic techniques for polymer electrolyte fuel cells continue to provide unique insight into the internal operation of these devices and lead to improved performance and durability. Localised measurements of current density have proven to be extremely useful in designing better fuel cells and identifying optimal operating strategies, with electrochemical impedance spectroscopy (EIS) now routinely used to deconvolute the various losses in fuel cells. Combining the two techniques provides another dimension of understanding, but until now each localised EIS has been based on 2-electrode measurements, composed of both the anode and cathode responses. This work shows that a reference electrode array can be used to give individual electrode-specific EIS responses, in this case the cathode is focused on to demonstrate the approach.

In addition, membrane hydration dynamics are studied under current load steps from open circuit voltage. A three-stage process is identified associated with an initial rapid reduction in membrane resistance after 10 s of applying a current step, followed by a slower ramp to approximately steady state, which was achieved after ∼250 s. These results support previously published work that has looked at membrane swelling dynamics and reveal that membrane hydration/membrane resistance is highly heterogeneous.

聚合物电解质燃料电池定制诊断技术的进步继续为这些设备的内部操作提供了独特的见识，并提高了性能和耐用性。电流密度的局部测量已被证明在设计更好的燃料电池和确定最佳运行策略方面极为有用，而电化学阻抗谱（EIS）现在已常规用于消除燃料电池中的各种损失。两种技术的结合提供了另一种理解的方式，但是直到现在，每个局部EIS都基于两电极测量，该测量由阳极和阴极响应组成。这项工作表明，参考电极阵列可用于给出各个电极特定的EIS响应，在这种情况下，将重点放在阴极上以演示该方法。

此外，研究了在开路电压下电流负载阶跃下的膜水化动力学。确定了一个三阶段过程，该过程与施加电流阶跃10 s后膜电阻初始快速降低有关，然后是约250 s后达到近似稳定状态的较慢斜坡。这些结果支持了以前发表的研究膜溶胀动力学的工作，并揭示了膜水合/膜抗性是高度异质的。