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

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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.