Impact of Multiphase Mass and Energy Transport Processes on Water Electrolysis in Polymer Electrolyte Membrane Cells

由于配电系统中可再生能源的不断增加，剩余电能供应的增加是可以预见的。在这种情况下，水电解是能够将电能转化为氢气的关键技术，氢气可用作能量存储介质或可供入化学工业的价值链。除了传统的碱性水电解之外，基于聚合物电解质膜（PEM）的水电解技术已经讨论了几年，这是本资助提案的焦点。PEM水电解的特别优点是可获得的电流密度更高、电压效率更高和负载灵活性更高。目前的缺点包括与碱性水电解相比，技术成熟度低得多，寿命短，比成本高。PEM电解池成本较高的主要原因是，除了在这些池中使用的昂贵材料之外，将来应该建造大规模PEM电解堆的单个池的尺寸太小。进一步增加电解槽面积的前提是全面理解PEM电解槽中发生的两相质量和能量传输现象。控制这些传输现象对于电解槽的最佳工艺操作和最佳设计至关重要。因此，本文提出的项目的目的是分析和量化两相质量和能量传输现象对PEM电解槽性能的影响。该工作计划包括（1）多孔集电器、催化层和聚合物电解质膜中的局部传输现象的实验表征和基于模型的描述，（2）电解槽的阳极流动通道中发生的传输现象的实验表征，以及（3）研究在通道和膜电极组件中发生的传输过程的耦合，以及它们对电池整体操作行为的影响。

Due to the continuous increase of renewable energy in the energy distribution system, the increase of surplus electrical energy supply is foreseeable. In this context, water electrolysis is a key technology able to convert electrical energy into hydrogen which can be used as energy storage medium or can be fed into the value chains of the chemical industries. Besides conventional alkaline water electrolysis, a water electrolysis technology based on a Polymer Electrolyte Membrane (PEM) is discussed since several years, which is the focus of this grant proposal. The particular advantages of PEM water electrolysis are higher attainable current densities, higher voltage efficiency, and higher load flexibility. Current disadvantages include far lower technical maturity, shorter life time, and higher specific costs compared to alkaline water electrolysis. The main reason for the higher costs of PEM electrolysis cells is, apart from expensive materials used in these cells, the far too small dimension of the single cells from which large-scale PEM electrolysis stacks should be built in the future. The prerequisite for the further increase of the cell area is the comprehensive understanding of the two-phase mass and energy transport phenomena taking place in PEM electrolysers. Controlling these transport phenomena is of paramount importance for optimal process operation and optimal design of the electrolysis cells. Thus, the aim of the here proposed project is to analyze and quantify the impact of two-phase mass and energy transport phenomena on the performance of PEM electrolysis cells. The work plan comprises (1) the experimental characterization and the model-based description of the local transport phenomena in the porous current collectors, the catalytic layers and the polymer electrolyte membrane, (2) the experimental characterization of the transport phenomena occurring in the anode flow channels of the electrolysis cell, and (3) the investigation of the coupling of transport processes taking place in the channel and in the membrane-electrode assembly, as well as their impact on the operational behavior of the cell as a whole.