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

在21世纪，随着可再生能源的使用日益增多，能源的储存是一项重大挑战。以CO2为原料，在液态或气态碳氢化合物中以化学能的形式储存电能是很有吸引力的，其中一种可能的途径是在电解液中电化学还原CO2。然而，大多数电催化剂需要很高的过电压，并且要么导致不太理想的产物CO或甲酸，要么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二氧化碳电化学还原，它与初级产品甲醇在相当低的过电压下进行。然而，电催化过程的机理尚不清楚，这阻碍了它在技术应用上的进一步优化。我们打算用表面科学的电化学方法对关键反应步骤进行系统的研究。为此，我们将首先用表面敏感红外光谱技术和电化学方法研究Ar饱和电解液中的吡啶在多晶铂和三种低指数铂单晶表面上的吸附。然后，我们将重复这些研究，将二氧化碳溶解在电解液中。此外，二氧化碳还原产物将使用差示电化学质谱(DEM)以及气(GC)和液(HPLC)色谱进行分析。此外，还将考察不同支持电解质的影响。最后，我们将利用DEM和高效液相色谱研究吡啶对电化学还原的稳定性。这些研究的最终目的是推导出吡啶催化的二氧化碳在铂电极上还原的综合反应机理。

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.