Electrochemical pressure impedance spectroscopy for transport characterization in electrochemical cells

电化学压力阻抗谱（EPIS）对含有气态反应物的电池中的传输过程具有很高的灵敏度（gr<e:1>， Bessler等，2016）。这种新技术是基于通过电流激励/压力检测或压力激励/电压检测来分析动态电流/电压/压力行为，频率范围为100 Hz至1 mHz。对于聚合物电解质膜燃料电池（PEMFC）， EPIS有望实现对流动和质量输运现象的高精度观测。这些现象，包括气体扩散层中的气体传输、催化剂支撑以及产出水的排出，决定了电池在大电流运行时的性能。输运现象的多样性，它们与电化学和温度的耦合，以及对孔隙大小和尺寸分布等结构性质的依赖，使得理解和建模变得困难。传统的技术，特别是电化学阻抗谱（EIS），很难区分传输现象，它们的信号可能（部分）被电荷转移过程掩盖。本提案的关键假设是EPIS可以显著提高pemfc中输运相关现象的测量灵敏度和准确性。因此，我们提出了一项结合实验和建模的EPIS用于pemfc的研究。具有压力激发和检测的单细胞装置将由法国国家科学研究中心-洛林大学（CNRS，法国）开发和操作。德国奥芬堡应用科学大学（HSO）将开发一个动态多物理场模型，并将其用于数据分析。该研究的主要目标是开发和评估EPIS用于PEMFC诊断。此外，该研究预计将对电池中涉及气体和液态水的不同输运现象的理解、表征和量化做出重大贡献。最后，为了显著降低整体诊断技术的成本，将测试使用低成本的压力激励和/或检测设备，如扬声器和/或压力传感器。我们的愿景是EPIS可以成为日常实验室实践中的标准诊断工具，以有限的额外努力（财务和技术）补充EIS，但大大提高了产出。这个为期三年的项目将包括两个合作伙伴之间的持续互动，CNRS负责实验部分和数据生成，HSO负责模型开发和数据解释。工作包包括实验和模型的准备阶段；EPIS工具的开发和使用，包括测量设备和仿真工具；对结果的解释；以及对EPIS技术的评价和评估。

Electrochemical pressure impedance spectroscopy (EPIS) shows a high sensitivity towards transport processes in cells with gaseous reactants (Grübl, Bessler et al. 2016). This novel technique is based on analyzing the dynamic current/voltage/pressure behavior by either current excitation/pressure detection or pressure excitation/voltage detection with frequencies in the range of 100 Hz to 1 mHz. For polymer electrolyte membrane fuel cells (PEMFC), EPIS is expected to allow the observation of flow and mass transport phenomena with high accuracy. These phenomena, covering gas transport in the gas diffusion layers and the catalyst support as well as evacuation of the produced water, govern the cell performance at high-current operation. The diversity of transport phenomena, their coupling with electrochemistry and temperature, and dependence on structural properties such as pore sizes and size distributions makes understanding and modeling difficult. With conventional techniques, in particular electrochemical impedance spectroscopy (EIS), transport phenomena are difficult to be distinguished from each other and their signal may be (partially) masked by charge-transfer processes.The key hypothesis governing the present proposal is that EPIS can significantly increase measurement sensitivity and accuracy of transport-related phenomena in PEMFCs. We therefore propose a combined experimental and modeling study of EPIS for PEMFCs. A single-cell setup with pressure excitation and detection will be developed and operated by CNRS - Université de Lorraine (CNRS, France). A dynamic multi-physics model will be developed and used for data analysis by Offenburg University of Applied Sciences (HSO, Germany). The primary goal of the study is the development and evaluation of EPIS for PEMFC diagnosis. In addition, the investigation is expected to bring a significant contribution on understanding, characterization and quantification of the different transport phenomena involving gases and liquid water in the cell. Finally, the use of low-cost pressure excitation and/or detection equipment such as a loudspeaker and/or pressure sensors will be tested, for the sake of significant reduction in the cost of the overall diagnosis technique. Our vision is that EPIS can become a standard diagnosis tool in everyday lab practice complementing EIS with limited add-on effort (financially and technically) but strongly enhanced output.The three-year project will consist in continuous interaction between the two partners, CNRS being in charge of the experimental part and generation of data, HSO working on model development and data interpretation. The work packages include a preparative phase for experiments and models; the development and the use of the EPIS tool covering the measurement device and the simulation tool; interpretation of the results; and evaluation and assessment of the EPIS technique.