The figure illustrates the interaction of CO2 molecule with the metal surfaces, which are located at the same distance from the on-top metal atoms. The analysis shows that the transfer of the partial negative charge to CO2 molecule is more prominent in the presence of the Au surface compared to the Zn surface. The charge transfer from the negatively charged Zn slab to the CO2 molecule is found to be rather insignificant and even negative ((CO2): +0.002) compared to that of Au ((CO2): - 0.241), which can explain the lower activity for CO2 reduction on Zn. In addition, DFTB calculations were performed to investigate the intrinsic affinity of the two metal slabs with the CO2 molecule in the absence of negative charge. The results reveal that CO2 has a stronger interaction with a neutral Au slab compared to a neutral Zn slab, resulting in a shorter equilibrium distance and a smaller OCO bond angle (as summarized at the top of Figure 5.4). These findings suggest that the affinity of Zn metal towards CO2 is noticeably lower than that of Au, which can be attributed to differences in their electronic properties and surface energies105. The results presented in Figure 5.4 lend support to the hypothesis that the initial electron transfer to adsorbed CO2 represents the rate-determining step for catalysts located on (CO2):+0.002, <OCO>:180, dis:319.43 pm Figure 5.4. Mulliken population analysis for CO2 interacting with negatively charged metal slabs, calculated using single-point BAND calculations. Subfigures (a) and (b) illustrate the results for CO2 interacting with Zn and Au 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. The figure highlights the results for charge transfer ((CO2)) from BAND calculations, along with the CO2 bond angle (<OCO>) and the equilibrium distance from the surface (dis: in picometer) from DFTB calculations, which are summarized at the top. a) b) (CO2):-0.241, <OCO>:175.5, dis:307.4
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