In Chapter 3, it was demonstrated that imidazolium cation influences the electron density of adsorbed CO2 by interacting with the C2-proton. This interaction results in a lower energy barrier for the formation of highly polarized adsorbed *CO2 .- when imidazolium cations are present. Thus, the primary cause of the modified differences in activity between various transition metal catalysts examined in this study, especially those with high energy barriers for CO2 adsorption (such as the Zn, Au, and Ag electrodes), is expected to be the reduction of the energy barrier for the formation of polarized intermediates, aided by H-bond formation. The simplified microkinetic model presented in Supporting Information Section IV demonstrates that the kinetics of the first electron transfer step leading to chemical adsorption of CO2 impact the overall reaction rate, even for catalysts where CO desorption is the rate-determining step. Therefore, for catalysts such as Ni and Cu, the primary function of imidazolium cation in stabilizing the CO2 adsorbed intermediate can still be in effect to modulate the overall reaction rate. However, it is important to note that obtaining the equilibrium constant for CO2 adsorption, facilitated by imidazolium cation, and accurately quantifying its influence on the overall reaction rate for catalysts with CO desorption as the rate-determining step, necessitates a -2 -1.6 -1.2 -0.8 -0.4 0.0 Figure 5.6. Volcano plot of CO2 reduction activity for transition metal catalysts. (a) obtained in this work for anhydrous MeCN and 0.5 % mol MM NTf2 as promotor. (b) obtained for aqueous media from work of Jaramillo and co-authors 7. b) a)
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