Miikroelectrochemical investigation of the oxygen and CO2 reduction at gas diffusion electrodes

在第一个供资期间已经使用的银/聚四氟乙烯GDEs的应用范围将扩大到目前在工业氯碱电解过程中催化氧还原反应的用途。我们已经能够证明，电化学反应，如产生ORR的氢氧化物，对反应环境造成了鲜为人知的实质性影响。预计氢氧化物的局部活性增加，而水的活性降低，由于局部pH升高和反应物溶解度的变化，导致反应速度减小。我们希望使用在配位项目(KO)和TP1(Turek)中制备的基于银/聚四氟乙烯的GDEs来进行二氧化碳的电化学还原，同时通过ORR调节局部pH。众所周知，银主要产生H2和CO2，因为所需的电势重叠。我们假设，通过调节局部反应环境，可以将CO2RR的选择性转移到CO的生成上。提高局部pH可以抑制寄生析氢(HER)，进而提高CO的法拉第效率。此外，我们计划利用在第一个资助期开发的基于SECM的方法来研究CO2RR对电化学环境的影响。通过对基于SECM的方法的改进，我们想要阐明GDE内部的局部动态变化。此外，所获得的洞察力将使用概念上新的拉曼池的振动光谱学来验证。我们希望能够从实验上验证TP1(Turek)和TP2(Kreyer)的模拟，并为新的GDE模型定义复杂的输入参数。此外，我们计划在毛细管内进行模型电润湿实验，作为TP4(Manke)和TP5(Nieken)的输入。

The application of the silver/PTFE GDEs already utilized during the first funding period will be extended beyond its present use for the catalysis of the oxygen reduction reaction (ORR) in the context of the industrial chlor-alkali electrolysis process. We were already able to show that elec-trochemical reactions, such as the hydroxide producing ORR, pose a barely acknowledged yet substantial influence on the reaction environment. It is expected that the local activity of hydroxide rises whereas the water activity is decreasing, leading to a diminished reaction rate due to a rise in the local pH and a change in the reactant solubility. We want to use silver/PTFE based GDEs fabricated in the coordination project (KO) and in TP1 (Turek) for the electrochemical reduction of CO2 with concurrent modulation of the local pH via the ORR. Silver is known to yield mainly H2 and CO2 because of an overlap of the required potentials. We hypothesize that the selectivity of the CO2RR can be shifted towards the production of CO by modulating the local reaction environ-ment. Increasing the local pH may inhibit the parasitic hydrogen evolution (HER) which in turn would increase the faradaic efficiency for CO. In addition, we plan to investigate the influence of the CO2RR on the electrochemical environment utilizing a SECM based methodology that was developed during the first funding period. By modification of SECM based methods we want to elucidate local dynamic changes inside the GDE. Furthermore, the gained insights shall be valida-ted using vibrational spectroscopies with a conceptually new operando Raman cell. We expect to be able to experimentally validate simulations from TP1 (Turek) and TP2 (Krewer) and to define sophisticated input parameters for novel GDE models. Moreover, we plan to perform model electrowetting experiments in capillaries as input for TP4 (Manke) and TP5 (Nieken).