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

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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).