the left side of the volcano plot, as depicted in Figure 5.3. Conversely, metals such as Cu and Ni, which exhibit stronger binding to CO than Au, exhibit slower kinetics. This indicates that for these catalysts with strong CO binding, CO desorption is likely the rate-determining step. To gain deeper insights into the stronger interaction between Cu and CO compared to Au and CO, DFT calculations were utilized to analyze the Mulliken population of CO and negatively charged Au and Cu slabs (Figure 5.5). The results confirm a more robust interaction between CO and the Cu slab, as indicated by a larger partial negative charge transfer from the Cu slab to the CO molecule compared to the Au slab (((CO2): -0.105 for Cu vs ((CO2): -0.072 for Au ). Volcano plot presented in this study serves as a useful tool for predicting the reactivity of transition metal catalysts in non-aqueous CO2 reduction based on their CO adsorption. Moreover, electronic models, such as the d-band model, which leverage the electronic properties of the metal, particularly the d-band center (106-107, have successfully been utilized to predict CO adsorption with transition metals (also see the Theoretical Appendix at the end of this chapter). Therefore, combining electronic models with the Volcano plot in this work (CO):-0.105 Figure 5.5. Mulliken population analysis for CO interacting with negatively charged metal slabs, calculated using single-point BAND calculations. Subfigures (a) and (b) illustrate the results for CO interacting with Au and Cu slabs, respectively. The figure highlights the charge differences between the top metal atom and its surroundings, as well as the negative charges found on oxygen atoms and positive charges found on carbon atoms. Details of charge transfer results are also summarized at the top. a) b) (CO):-0.072
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