Obermaier Michael, Bandarenka Aliaksandr S, Lohri-Tymozhynsky Cyrill
BMW Group, 80788, Munich, Germany.
Energy Conversion and Storage - ECS, Physik-Department, Technische Universität München, James-Franck-Straße 1, 85748, Garching, Germany.
Sci Rep. 2018 Mar 21;8(1):4933. doi: 10.1038/s41598-018-23071-5.
Electrochemical impedance spectroscopy (EIS) is an indispensable tool for non-destructive operando characterization of Polymer Electrolyte Fuel Cells (PEFCs). However, in order to interpret the PEFC's impedance response and understand the phenomena revealed by EIS, numerous semi-empirical or purely empirical models are used. In this work, a relatively simple model for PEFC cathode catalyst layers in absence of oxygen has been developed, where all the equivalent circuit parameters have an entire physical meaning. It is based on: (i) experimental quantification of the catalyst layer pore radii, (ii) application of De Levie's analytical formula to calculate the response of a single pore, (iii) approximating the ionomer distribution within every pore, (iv) accounting for the specific adsorption of sulfonate groups and (v) accounting for a small H crossover through ~15 μm ionomer membranes. The derived model has effectively only 6 independent fitting parameters and each of them has clear physical meaning. It was used to investigate the cathode catalyst layer and the double layer capacitance at the interface between the ionomer/membrane and Pt-electrocatalyst. The model has demonstrated excellent results in fitting and interpretation of the impedance data under different relative humidities. A simple script enabling fitting of impedance data is provided as supporting information.
电化学阻抗谱（EIS）是用于聚合物电解质燃料电池（PEFC）非破坏性原位表征的不可或缺的工具。然而，为了解释PEFC的阻抗响应并理解EIS揭示的现象，人们使用了许多半经验或纯经验模型。在这项工作中，开发了一个相对简单的无氧气存在下的PEFC阴极催化剂层模型，其中所有等效电路参数都具有完整的物理意义。它基于：（i）催化剂层孔隙半径的实验量化，（ii）应用De Levie的解析公式计算单个孔隙的响应，（iii）近似每个孔隙内的离聚物分布，（iv）考虑磺酸基团的特异性吸附，以及（v）考虑通过约15μm离聚物膜的少量氢渗透。所推导的模型实际上仅有6个独立的拟合参数，且每个参数都有明确的物理意义。它被用于研究阴极催化剂层以及离聚物/膜与铂电催化剂界面处的双层电容。该模型在拟合和解释不同相对湿度下的阻抗数据方面显示出优异的结果。作为支持信息提供了一个能够拟合阻抗数据的简单脚本。
