NSERC-DFG SUSTAIN: Hierarchically structured cathode catalyst layers prepared by spinodal decomposition for PEM Fuel Cells - From fundamental understanding to application at operation conditions

利用氢能发电的质子交换膜燃料电池(PEMFC)被认为是能源转换的关键技术。在这个国际项目中，我们解决了质子交换膜燃料电池中低效阴极催化层(CL)的当前挑战，开发了一种量身定制的分层结构，以改善催化剂的可及性和质量传输。具有独特的质子供应、氧气和水传输通道的CL的最佳结构将通过调幅分解来实现。在这种方法中，两个或两个以上组分的均匀混合物经历触发相分离，允许制备在远离平衡的网络中停滞的分层结构材料。然而，调幅节点分解还没有被应用于设计用于质子交换膜燃料电池的高效CLS。我们联合体的初步结果验证了这一概念的可行性，并导致了性能增强的质子交换膜燃料电池非常有希望的初步结果。改变分离液、催化剂颗粒和离聚体结构的性质，结合工艺条件，允许多种因素来控制最终的分层结构。导电原子力显微镜(c-AFM)将被用来显示结构中的质子传导通道，并将它们与具有高空间分辨率的AFM-扫描电化学显微镜(SECM)相结合的高电化学活性区域相关联。最后，在器件级上表征了可获得的铂电化学活性表面积(ECSA)和CL内部的氧传输电阻。同时，新CLS的整体性能以传统最先进的CLS为基准。在这个项目中，我们的目标是弥合结构、微观行为(如局部电催化活性和离聚体-催化剂相互作用)之间的差距，并改善设备性能。通过微观流变学、原子力显微镜和电化学方法，从微观和宏观两个方面研究了改善氧气传输和铂可及性的关键因素。得到的链接将用于基于调幅节点分解的层次结构优化。通过结合在微观和宏观尺度上确定的性质和器件级别的性能，我们的目标是在微观行为和其宏观结果之间建立联系。基于这种结构-功能关系，我们将优化分级结构的阴极催化剂层，以获得更好的铂利用率和改善的质量传输。在我们的跨学科项目中，我们将复杂的制备与先进的表征和设备级电化学相结合，开发出一种复杂、仍具有成本效益且易于工业化的新型CL，以增强PEMFC的性能。

Proton exchange membrane fuel cells (PEMFCs) for harnessing electrical energy from hydrogen are considered a key technology in the energy transition. In this international project we tackle the current challenges of an inefficient cathode catalyst layer (CL) in PEMFCs by developing a tailored hierarchical structure for improved catalyst accessibility and mass transport. The optimal architecture of the CL with distinctive channels for proton supply, oxygen and water transport will be realized by spinodal decomposition. This method, in which a homogeneous mixture of two or more components undergoes a triggered phase separation, allows the preparation of hierarchically structured materials, arrested in far-from-equilibrium networks. However, spinodal decomposition has not yet been applied to design highly efficient CLs for PEMFCs. Preliminary results from our consortium verified the feasibility of the concept and resulted in very promising initial results of PEMFCs with enhanced performance. Varying the nature of the demixing fluids, catalyst particles and ionomer architecture in combination with processing conditions allows for multiple factors to control the final hierarchical structure. Conductive atomic force microscopy (c-AFM) will be employed to visualize proton conductive channels in the structure and relate them to localized highly electrochemically active regions, as investigated by combined AFM - Scanning Electrochemical Microscopy (SECM) with high spatial resolution. Finally, the overall accessible Pt electrochemical active surface area (ECSA) and the oxygen transport resistance inside the CL are characterized on the device-level. At the same time, the overall performance of the new CLs is benchmarked to conventional state-of-the-art CLs. Within this project we aim to bridge the gap between structure, microscopic behavior like local electrocatalytic activity and ionomer-catalyst interaction, and improved device performance. The key improvement factors for O2 transport and Pt accessibility are investigated on the micro- and macroscale by microrheology, AFM and electrochemical methods. The gained link will be used to optimize the hierarchical structure based on spinodal decomposition. By combination of the properties determined on the micro- and macroscale and the device-level performance, we aim to establish a link between the microscopic behavior and its macroscopic consequence. Based on this structure-function relationship, we will optimize the hierarchically structured cathode catalyst layers to obtain a superior Pt utilization and improved mass transport. In our interdisciplinary project we combine sophisticated preparation with advanced characterization and device-level electrochemistry to develop a complex, still cost-effective and easy to industrialize, new CL for enhanced PEMFC performance.