According to Figure 5.3, metals such as Ag and Zn, which have lower CO binding energy than Au, demonstrate lower CO2 reduction activities than Au. Based on this observation, we can infer that for these catalysts, the first electron transfer, which causes the chemical adsorption of CO2 over the catalyst site 19, is the rate-determining step for CO2 reduction. This hypothesis is consistent with our earlier findings in Chapter 3, which demonstrated that the electron transfer from the Au electrode to the CO2 molecule upon its adsorption strongly depends on the composition of the imidazolium cation. Figure 5.4 provides a visual representation of the charge transfer process from negatively charged Au and Zn metal surfaces to CO2 molecule. Figure 5.3. (a) Volcano plot illustrating current density obtained from chronoamperometry data under stirring conditions for CO2 reduction at -2 V versus CO binding strength, results are normalized against geometric surface area, (b) LSVs for Ni and Cu electrodes; and (c) LSVs for Zn, Au, and Ag electrodes for CO2 reduction in anhydrous acetonitrile in quiescent solutions with a CO2 flow rate of 5 ml/min. In all experiments 0.5 mol% of MM NTf2 was used as both electrolyte and co-catalyst. b) c) a)
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