Development and Application of a Flexible Synthesis for Unprotected Colloidal Pt Nanoparticles as a Platform for Systematic Degradation Studies in Electrocatalysis

直接使用氢气作为能量载体是从核能和化石燃料转向可再生能源的一种可能方案。因此，燃料电池技术具有重要的相关性，为了促进其适用性，活性和稳定性的优化是必不可少的挑战。虽然过去对催化活性的研究已经相当深入，活性物质也已经开发出来，但关于催化剂性能与稳定性之间关系的知识仍然很少。拟建项目的主要目标是建立一个制备平台，以便系统研究最相关的催化剂性质（粒度、负载和支撑）对性能的影响，从而也影响催化剂的稳定性。对于最先进的燃料电池催化剂（碳负载Pt纳米颗粒）来说，这个任务基本上可以使用所谓的无保护Pt纳米颗粒（NPs）来解决。这些NPs在碱性乙二醇中以胶体的形式合成。应用进一步的制备步骤可以将这些颗粒沉积到每种类型的支撑材料上。因此，支架和颗粒载荷可以独立控制。然而，未保护的NPs的应用仍然受到对粒径控制有限的阻碍。任何通过热驱动制备方案实现粒度控制的尝试都没有给出任何令人满意的结果。然而，最近的研究表明，不受保护的NPs也可以用光化学方法合成。为了实现适当的粒径控制，应在拟议的项目中研究这种迄今尚未开发的控制无保护NPs合成的潜力。这样的合成方案最终将能够系统地、独立地研究与催化相关的材料特性（粒度、负载和支撑）的影响。对于燃料电池，已经确定了不同的降解机制。然而，这些机制对催化剂的颗粒大小和颗粒负载的依赖性仍未确定。因此，该项目的第二部分将通过使用先前开发的合成协议来关注该主题。模型催化剂将通过在TEM网格碳膜上沉积NPs来制备。此外，计划应用STEM（扫描透射电子显微镜）作为实验工具，以建立一种自动化，快速的粒度分析方法。与IL-TEM（同位置透射电子显微镜）的既定方法相比，STEM的使用不仅可以进行局部分析，还可以在合理的时间框架内调查更大的区域。这将从长远的角度不仅可以得出关于个别退化机制的相关性的定性结论，而且还可以得出定量结论。

The direct use of H2 as an energy carrier is one possible scenario for the switch from nuclear power and fossil fuels to regenerative energy. The fuel cell technology is thereby of significant relevance and the optimization of activity and stability are essential challenges in order to foster their applicability. While the catalytic activity has been investigated quite intensively in the past and active material have been developed, knowledge about relations between the catalyst properties and the stability are still scarce. The primary goal for the proposed project is to establish a preparation platform that enables for systemic investigations of the influence of the most relevant catalyst properties (particle size, loading, and support) on the performance and hence also the catalyst stability. For state-of-the-art fuel cell catalysts (carbon supported Pt nanoparticles) this task can basically be addressed using so-called unprotected Pt nanoparticles (NPs). Such NPs are synthesized as colloids in alkaline ethylene glycol. The application of further preparation steps enables for depositing these particles onto every type of support material. As a result support and particle loading can be controlled independently. However, the application of unprotected NPs is still hindered by the limited control over particle size. Any attempt to achieve particle size control by thermally driven preparation protocols did not give any satisfying results. However, recent investigations have shown that unprotected NPs can also be synthesized using photochemical methods. This so far unexplored potential for controlling the synthesis of unprotected NPs shall be investigated within the proposed project in order to achieve an appropriate particle size control. Such a synthesis protocol will ultimately enable for investigating systematically and independently the influence of the catalytically relevant material properties (particle size, loading, and support).For fuel cells different degradation mechanisms have been identified. The dependence of these mechanisms on the particle size and particle loading of the catalyst has however still not been determined. Therefore, the second part of the project will focus on this topic by using the previously developed synthesis protocol. Model catalysts will be prepared by deposition of the NPs onto TEM grid carbon films. Furthermore, the application of STEM (scanning transmission electron microscopy) as an experimental tool is planned in order to establish an automated, fast method for performing particle size analyses. In contrast to the established methodology of IL-TEM (identical location transmission electron microscopy) the use of STEM enables not merely for local analysis but also for investigating larger areas within a reasonable time frame. This will perspectively allow not merely for qualitative but also quantitative conclusions regarding the relevance of individual degradation mechanisms.