by some studies56 for electrodes such as Cu resulted in poor electrochemical results with unassigned peaks (Supporting Information Figures S2.7a-S2.7c) . Thus, it is recommended to avoid electrochemical cleaning with non-noble metals, and if necessary, rigorous sandpaper polishing (mechanical cleaning) should be applied. The glass reactor, reference compartment, graphite rod, gas inlet, and gas outlet tubes underwent a thorough rinsing process using Milli-Q water, ethanol, and HPLC grade acetonitrile. Subsequently, the working electrode and all other reactor components were assembled, and the entire setup was sonicated for 2 sets of 5 minutes using HPLC grade acetonitrile. Following this step, the reactor was subjected to a continuous purge of super dry helium (Helium A/Zero Grade N4.6, Linde) for a duration of 30 minutes prior to the introduction of the electrolyte. In experiments involving CO2, a dryer (ZPure DS H2O, ChromRes) was employed to ensure the complete removal of moisture from the CO2 inlet (Carbon Dioxide Food Grade, Linde) before it entered the reactor. This additional step ensured that the CO2 supplied to the reactor was free from any residual moisture. Figures S2.1 displays the results of SEM and EDX analysis from Ni and Au electrodes after the above-mentioned cleaning procedure. The surface appears to be sufficiently clean for being tested in electrochemical experiments. Counter electrode. A graphite rod was chosen as the counter electrode to mitigate additional artifacts resulting from metal oxidation and subsequent deposition onto the working electrode. The choice of counter electrode plays a crucial role in the electrochemical CO2 reduction process. Figure 2.1 presents a comparison of chronoamperometry results for CO2 reduction on an Au electrode using different counter electrodes: Au and Ag (Figure 2.1a) as well as graphite (Figure 2.1b). The results show that employing Au and Ag as counter electrodes leads to an increase in current, suggesting the occurrence of additional reactions. On the other hand, when graphite is used as the counter electrode, the performance of the CO2 reduction remains stable,
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