Multi-in situ Electrochemical Impedance Analysis of Biofuel Cell Performance (Supporting Information)

Electrochemical impedance spectroscopy (EIS) provides valuable insights into the interfacial kinetics and mass-transport behavior of an electrochemical system. However, conventional steady-state EIS cannot sufficiently capture transient processes in enzymatic biofuel cells (EBFCs), wherein electrode/electrolyte interactions evolve dynamically. In this study, we demonstrate a multi-in situ impedance method applicable to glucose/O2 EBFCs that employ MgO-templated carbon electrodes. Chronopotentiometry reveals that lower current densities induce higher glucose utilization efficiencies, reflecting the balance between the rates of substrate diffusion and surface reactions. In situ impedance analysis further differentiates the electrode-specific degradation: the cathode exhibits progressively increasing charge-transfer resistance attributable to enzyme and mediator leaching, whereas the anode displays non-monotonic resistance changes linked to overpotential-driven kinetics. Equivalent circuit modeling confirms that the cathodic overpotential is responsible for accelerating charge-transfer processes, leading to smaller semicircular features in the Nyquist plot over time. These results highlight the utility of multi-impedance measurements in identifying the performance-limiting factors in an EBFC under operational conditions. This approach provides mechanistic insights into enzyme stability, mediator retention, and substrate transport, and it serves as a diagnostic tool for the rational design of next-generation bioelectrochemical energy devices.

电化学阻抗谱（Electrochemical impedance spectroscopy, EIS）可为电化学体系的界面动力学与传质行为提供极具价值的研究视角。然而，传统稳态电化学阻抗谱无法充分捕捉酶生物燃料电池（enzymatic biofuel cells, EBFCs）中的瞬态过程——此类体系中电极与电解质的相互作用处于动态演化之中。本研究提出一种适用于采用氧化镁模板碳电极（MgO-templated carbon electrodes）的葡萄糖/氧气型酶生物燃料电池的多原位阻抗测试方法。计时电位法（Chronopotentiometry）的研究结果显示，较低的电流密度可提升葡萄糖利用效率，这一现象反映了底物扩散速率与表面反应速率之间的平衡关系。原位阻抗分析可进一步区分电极特异性降解行为：阴极的电荷转移电阻（charge-transfer resistance）随时间逐渐升高，这可归因于酶与介体的浸出；而阳极的电阻变化则呈现非单调特征，与过电位驱动的动力学过程相关。等效电路建模（Equivalent circuit modeling）证实，阴极过电位会加速电荷转移过程，导致奈奎斯特图（Nyquist plot）中的半圆特征随时间逐渐缩小。上述研究结果凸显了多阻抗测试方法在识别运行条件下酶生物燃料电池性能限制因素方面的应用价值。该方法可为酶稳定性、介体保留与底物传质机制提供深入见解，同时可作为下一代生物电化学能源装置合理化设计的诊断工具。