Fast in situ - spectroscopy of electrocatalytic fuel cell reactions - Methodic development and mechanistic studies

在本项目中，我们提出了在连续反应和连续电解质流动条件下进行原位红外光谱研究的新方法，这对于在实际反应条件下研究电催化燃料电池反应具有特殊的意义。这些方法将允许i)在微观结构模型系统上以大约50µs的（系统）时间分辨率对吸附物质进行极快的原位测量，以及ii)在燃料电池相关条件下对负载催化剂进行原位红外、原位质谱和电化学测量（见上文）。前者包括设计和建造一个带有微电极的特殊微流池，并通过红外显微镜进行步进扫描红外检测，将以前所未有的时间分辨率进行时间分辨原位光谱研究。这对于非平稳条件下的研究尤其有价值，因为它能产生反应过程初始阶段的机理信息。后者是基于衰减反射（ATR）几何形状的FTIR测量，它需要开发新型电极，在导电、电化学惰性和足够红外透明的衬底上有负载催化剂薄膜，这将使我们能够同时获得反应条件下实际负载催化剂上吸附和挥发、解吸物质的电化学数据和原位光谱信息。由于时间分辨率和材料要求的不同，这些方法具有很强的互补性。这些技术对于低温聚合物电解质燃料电池（pefc）中有机分子电氧化的原位研究特别有趣，其中由于复杂的反应方案，机理理解至关重要地依赖于反应条件下挥发性解吸物质和吸附物质的知识，并且，出于同样的原因，安装测量可以显著地增加机理理解。因此，作为概念的证明，我们将证明这些技术的可行性和贡献，以了解电催化燃料电池反应在有机分子，特别是低醇的电氧化动力学和机理研究中的作用。

In this project we propose to develop new methods for in-situ IR spectroscopic studies under continuous reaction and continuous electrolyte flow conditions, which are of particular relevance for the investigation of electrocatalytic fuel cell reactions under realistic reaction conditions. These methods shall allow i) extremely fast in-situ measurements of adsorbed species with a (system) time resolution of about 50 µs on microstructured model systems, and ii) combined insitu IR, in-situ mass spectrometric and electrochemical measurements on supported catalysts under fuel cell relevant conditions (see above). The former, which involves the design and build-up of a special micro-flow cell with a microelectrode and step-scan IR detection via an IR microscope, will allow time-resolved in-situ spectroscopic studies with an unprecedented time resolution. This is particularly valuable for studies under non-stationary conditions, which yield mechanistic information on the initial stages of the reaction process. The latter, which is based on FTIR measurements in an Attenuated Reflection (ATR) geometry and which requires the development of novel electrodes with a thin film of supported catalyst on a conducting, electrochemically inert, and sufficiently IR transparent substrate, will enable us to simultaneously acquire electrochemical data and in-situ spectroscopic information on the adsorbed and volatile, desorbing species on realistic supported catalysts under reaction conditions. Because of their different time resolution and material requirements these methods are highly complementary to each other. These techniques are particularly interesting for in-situ studies on the electrooxidation of organic molecules in low temperature polymer electrolyte fuel cells (PEFCs), where because of the complex reaction scheme a mechanistic understanding depends crucially on the knowledge of both volatile desorbing species and adsorbed species under reaction conditions, and where, from the same reason, instationary measurements can add significantly to the mechanistic understanding. As a proof of concept we will therefore demonstrate the feasibility and contribution of these techniques for the understanding of electrocatalytic fuel cell reactions in kinetic and mechanistic studies on the electrooxidation of organic molecules, in particular low alcohols.