shown for the Zn electrode in Figure S5.6. The figure clearly shows a considerable difference in the potential-current profiles under CO2 and He purge, with a notably larger Faradaic current around -2.0 V vs Ag/Ag+ under CO2 atmosphere, exclusively assigned to production of CO. The stability of the Ni electrode was visually assessed as shown in Figure S5.5. After 90 mins and after 10 hrs of electrolysis, the Ni surface appears clean and the solution is clear. Although many studies have reported high FEs for CO formation using Ag and Au catalysts 38, 71, 104, particularly in aqueous media, to our best knowledge, this is the first study to demonstrate close to 100% FE for CO formation with polycrystalline Ni, Zn, and Cu electrodes (Gas analysis and Faradaic efficiency evaluations can be found inSupporting Information Section V). The study also uncovers an intriguing trend in the CO2 reduction activity of the various transition metal catalysts under near-steady-state conditions for 5 hours. In particular, Au exhibited the highest activity, requiring the lowest potential to achieve the same current density, while Cu and Ag displayed nearly identical potentials. Conversely, Zn and Ni demonstrated the lowest activity. This finding offers valuable insights into the efficacy of different metals as catalysts for CO2 reduction in non-aqueous media. Jaramillo and co-workers performed a similar study in aqueous media, reporting CO2 reduction activity for several transition metal catalysts 7. In their study, Au and Ag were the only catalysts showing a FE greater than 90 percent for CO2 reduction. Zn and Cu showed, respectively, 80% and 68% FE for products of CO2 reduction (the remaining FE was assigned to the formation of H2), and Ni was reported to display a FE less than 5% for CO2 reduction with most of the electrons utilized for H2 evolution. Besides, Au and Ag were the only catalysts displaying FEs for CO formation at maximum levels of around 97% and 89%, respectively, at various potentials. Cu showed a very low FE for CO formation (around 1–2%), with 26% FE for ethylene and 24% FE for methane. In addition, a FE of 9.7% was reported for ethanol and 22.6% for H2. These results show that the combination of anhydrous MeCN and imidazolium cation studied in this work can outperform
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