质子交换膜燃料电池电化学阻抗谱弛豫时间分布研究

电化学阻抗谱技术能够获取燃料电池不同频率阻抗，但对阻抗的构成缺乏进一步解析，难以直接构建精准的等效电路模型进行阻抗拟合分析，而弛豫时间分布（Distribution of relaxation time，DRT）方法不需要定义特定的等效电路模型，即可解析燃料电池不同时间常数的极化过程。针对实验室用质子交换膜燃料电池，在不同运行条件下对其进行阻抗谱测量，并通过Kramers-Kronig关系验证所记录阻抗数据的质量。基于DRT分析方法，系统地解释阻抗谱中各频段阻抗对应的物理或化学意义。研究表明，该电池的电化学阻抗谱主要由3个不同时间常数频段的极化阻抗构成，通过与运行条件相关性的系统分析，确定低频段阻抗为氧气在多孔介质中的传输阻碍，中频段阻抗为与氧还原反应有关的电荷传递阻碍，中高频段阻抗为阴极催化剂层中的质子传输阻碍。为进一步确定DRT分析结果的合理性，采用等效电路模型拟合测量的阻抗数据，辨识的电阻元件参数变化趋势与DRT分析结果一致。

Distribution of Relaxation Times Analysis of Proton Exchange Membrane Fuel Cell Electrochemical Impedance Spectra

Electrochemical impedance spectroscopy (EIS) could obtain the magnitude of fuel cell impedance at different frequencies. Still, the composition of impedance lacks further analysis, and it is challenging to reconstruct an accurate equivalent circuit model (ECM) for fitting review directly. The distribution of relaxation time (DRT) method does not need to define a specific ECM to analyze the polarization process of different time constants. For the experimental proton exchange membrane fuel cell, the EIS measurements are performed under different operating conditions, and the quality of the recorded impedance data is verified by the Kramers-Kronig relationship. Based on the DRT analysis, the physical or chemical meanings of impedance in each frequency band are systematically analyzed. The results show that the EIS is mainly composed of the polarization impedance of three different time constant frequency bands. Through analysis of the correlation with operating conditions, the low-frequency impedance is determined to be the gas diffusion barrier in the porous media, and the mid-frequency impedance is attributed to the charge transfer obstacle inside the oxygen reduction reaction, and the mid-high-frequency impedance hinders the proton transport in the cathode catalyst layer. To further determine the rationality of the DRT analysis results, an equivalent circuit model is used to fit the measured impedance data, and the changing trend of the identified resistance element parameter is consistent with the DRT analysis results.