Dynamic state analysis of porous gas diffusion electrodes

在子项目2中，采用基于模型的动力学方法和实验动力学方法研究了银基气体扩散电极（GDE）中碱性氧还原反应（ORR）和二氧化碳还原反应（CO2RR）的宏观动力学。对电极内部的限制过程的基本理解将针对两种反应产生并进行比较。物质传输、相平衡和各种电化学反应步骤的复杂相互作用使得多孔电极中过程的分析和识别成为一项具有挑战性的任务。在用于二氧化碳还原的GDE的情况下，必须另外考虑化学反应和竞争的析氢反应。将研究电势、化学动力学和电极设计如何影响传输过程、物种分布以及电流密度。此外，将阐明单个过程对电极性能和动态行为的影响，并建立电极内部过程的定量动态模型来回答这些问题。验证所需的测量数据将由项目合作伙伴提供，并在自己的实验中使用差分电化学质谱法获得。动态技术允许一个单独分析过程，并确定其特征时间常数，动力学参数，以及它们对GDE性能的影响。对于具有ORR的GDE，电位和电流密度的阶跃是特别合适的动态输入信号，因为普遍存在缓慢的传输过程。其他子项目的结果，如详细的动力学，局部反应条件和电极内的电解质分布结合在建模中，以更好地了解单个过程对整体GDE行为的影响。此外，基于模型的分析选定的情况下，得出结论，改善电极的设计和操作条件。此外，动态和稳态的方法将进行比较，他们的优点和缺点，研究GDE和一般适用性的动态方法研究GDE将使用GDE与两个反应进行评估。

In sub-project 2, the macrokinetics of the alkaline oxygen reduction reaction (ORR) and the carbon dioxide reduction reaction (CO2RR) in silver-based gas diffusion electrodes (GDE) are investigated with model-based and experimental dynamic methods. A basic understanding of the limiting processes inside the electrodes will be generated for both reactions and compared. The complex interactions of species transport, phase equilibria and various electrochemical reaction steps render the analysis and identification of the processes in porous electrodes a challenging task. In case of GDEs for carbon dioxide reduction, chemical reactions and the competing hydrogen evolution reaction have to be considered in addition. It will be investigated how the potential, the chemical kinetics and the electrode design influence transport processes, species distribution as well as current density. Furthermore, the impact of single processes on performance and dynamic behaviour of the electrode will be elucidated.Quantitative dynamic models for the processes inside the electrode will be developed to answer these questions. The measurement data required for validation will be provided by the project partners and obtained in own experiments using differential electrochemical mass spectrometry. Dynamic techniques allow one to analyse processes individually and to determine their characteristic time constants, kinetic parameters, and their impact on the GDE performance. For the GDE with ORR, steps in potential and current density are particularly suitable dynamic input signals because of the prevalence of slow transport processes. The results from the other sub-projects such as detailed kinetics, local reaction conditions and electrolyte distribution inside the electrode are combined in the modelling to better understand the influence of individual processes on the overall GDE behaviour. Additionally, a model-based analysis of selected scenarios is conducted to draw conclusions for improving electrode design and operation conditions. Furthermore, dynamic and steady-state methods will be compared regarding their advantages and disadvantages for investigating GDE and the general suitability of dynamic methods for studying GDE will be evaluated using GDEs with both reactions.