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

由于可再生能源在能源分配系统中的不断增加，过剩电能供应的增加是可以预见的。在这种背景下，水电解是一项能够将电能转化为氢气的关键技术，氢气可以作为储能介质或馈送到化工行业的价值链中。除了传统的碱性水电解，基于聚合物电解质膜(PEM)的水电解技术也是几年来讨论的，这是这项赠款提案的重点。PEM水电解的独特优势是获得更高的电流密度、更高的电压效率和更高的负载灵活性。目前的缺点是与碱性水电解相比，技术成熟度低得多，寿命短，比成本高。PEM电解槽成本较高的主要原因是，除了这些电解槽所使用的昂贵材料外，未来应该用来建造大型PEM电解槽的单个电解槽的尺寸太小。进一步增加电解槽面积的前提是全面了解质子交换膜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优化工艺操作和电解槽的优化设计至关重要。因此，本项目的目的是分析和量化两相质量和能量传输现象对质子交换膜电解槽性能的影响。工作计划包括(1)多孔集电体、催化层和聚合物电解质膜中局部传输现象的实验表征和基于模型的描述，(2)电解槽阳极流道中发生的传输现象的实验表征，以及(3)通道和膜-电极组件中发生的传输过程的耦合及其对电池整体运行行为的影响的研究。

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.