Mechanistic Studies of Pyridine Catalyzed CO2 Reduction on Pt Electrodes: An Electrochemical Surface Science Approache

随着21世纪可再生能源的使用越来越多，能源的储存是一个重大挑战。将电能以化学能的形式储存在以CO2为原料的液态或气态烃中是一个很有吸引力的研究方向，其中一个可能的途径是CO2在水溶液电解质中的电化学还原。然而，大多数电催化剂需要高的过电压，并且导致不太期望的产物CO或甲酸，或者导致各种可能的还原产物的混合物。一个例外是吡啶催化的CO2电化学还原，其与主要产物甲醇在相当低的过电压下进行。然而，电催化过程的机理还不清楚，这阻碍了其进一步优化的技术应用，我们打算使用表面科学的电化学方法来系统地研究关键的反应步骤。为此，我们首先利用表面灵敏红外光谱技术和电化学方法研究了Ar饱和电解液中吡啶在多晶Pt和三种低指数Pt单晶表面的吸附。然后，我们将用溶解在电解质中的CO2重复这些研究。此外，CO2还原产物将采用差分电化学质谱法（DEMS）以及气相色谱法（GC）和液相色谱法（HPLC）进行分析。此外，将研究不同支持电解质的影响。最后，我们将使用DEMS和HPLC研究吡啶对电化学还原的稳定性。这些研究的最终目标是推导出一个全面的反应机理吡啶催化的二氧化碳还原铂电极。

The storage of energy is a major challenge accompanying the increasing use of renewable energy resources in the 21st century. To store electrical energy in form of chemical energy in liquid or gaseous hydrocarbons with CO2 as feedstock is obviously appealing, and one possible route is the electrochemical reduction of CO2 in aqueous electrolytes. Yet, most electrocatalysts require a high overvoltage and either lead to the less desirable products CO or formic acid or to a mixture of the various possible reduction products. An exception is the pyridine catalyzed electrochemical reduction of CO2, which proceeds at rather low overvoltage with the primary product methanol. However, the mechanism of the electrocatalytic process is still unclear, which hampers its further optimization towards technical application.We intend to use a surface science electrochemical approach to investigate the key reaction steps in a systematic way. Therefor, we will first investigate the adsorption of pyridine from Ar-saturated electrolytes on polycrystalline Pt and the three low-indexed Pt single crystal surfaces with surface sensitive infrared spectroscopic techniques as well as electrochemical methods. Then, we will repeat these studies with CO2 dissolved in the electrolyte. Furthermore, CO2 reduction products will be analyzed with differential electrochemical mass spectrometry (DEMS), as well as gas (GC) and liquid (HPLC) chromatography. Additionally, the effect of different supporting electrolytes will be investigated. Lastly, we will study the stability of pyridine towards electrochemical reduction using DEMS as well as HPLC. The final goal of these studies is to deduce a comprehensive reaction mechanism for the pyridine catalyzed CO2 reduction at platinum electrodes.