The lowest unoccupied molecular orbital (LUMO) of a bent CO 2 is highly localized at the C, whereas the highest occupied molecular orbital (HOMO) is highly localized at the O, making them strongly susceptible to interactions with nucleophiles and electrophiles respectively. We use Bader charge analysis 11 to quantify this susceptibility and to chart the reaction path for the first CPET step for CO 2 reduction, as depicted in Figure . In order for the C-H bond of * OCHO to form, * H with a partial negative charge (δ -) acts as a nucleophile for the C δ + of CO 2 (top panel in Figure ). Both Volmer-Tafel and Volmer-Heyrovsky mechanisms for the formation of H 2 also share the first CPET Volmer step of * H δ -formation (bottom panel in Figure ). This implies that the formation of * COOH competes with the Volmer step which is in-turn a prerequisite for the formation of * OCHO. Following the Volmer step, the * H can either participate in a Tafel or Heyrovsky step to form H 2 , or react with the CO 2 to form * OCHO. According to our analysis, there are therefore two reaction bifurcations before and after formation of * H that generally control the selectivity for CO 2 ER. An analogous finding has been recently reported for CO 2 ER on Cu(100) surfaces and as well as for the selectivity of CO 2 ER on metalloporphyrins. This approach can be further extended to the formation of higher CPET products from CO 2 ER such as methanol (CH 3 OH) and methane (CH 4 ) (see extended reaction scheme in Figure ). The thermodynamically most feasible routes for the formation of CH 3 OH and CH 4 go via * COOH followed by the * CHO species, as becomes clear from the UL for the various reaction pathways shown in Figures and. Extending the Bader charge analysis to these pathways, it is expected that the formation of * CHO from * CO forms through a surface bound * H interacting with the C δ+ . θ * H is therefore expected to play an important role in the formation of higher electron reduction products of CO 2 ER and this analysis can potentially be useful for studying catalysts such as Cu where these reaction steps become prominent. Interestingly, very recent experimental findings for CO 2 ER on Cu catalysts draw similar conclusions and indicate an important role of * H in the formation of CH 4 . Climbing image nudged elastic band (CI-NEB) calculations were performed to estimate the height of the activation barriers based on the reaction path analysis presented in Figure (see Computational Details section in SI). As can be seen in Figure , the activation barriers after correction for solvation for formation of * COOH and H 2 via Heyrovsky and Tafel steps are 0.93 eV, 0.79 eV and 0.77 eV respectively, with H 2 as the most thermodynamically favorable product. Interestingly however, there is no kinetic barrier for the formation of * OCHO involving the direct nucleophilic attack by * H (see Figures S3-S6 for uncorrected activation barriers, atomic configurations and excess partial charges of the initial, transition and final states). The high solvation energy of the transition state relative to the initial state for * OCHO (Table , Figure ) plays an important role in diminishing the activation barrier for its formation. This analysis highlights the importance of the consideration of solvation in theoretical mechanistic studies for CO 2 ER; a conclusion which is in agreement with what has been shown for other (electro)catalytic systems. The presence of cationic and anionic species in the electrolyte may also influence the binding energies and activation barriers for the formation of certain reaction intermediates and there are ongoing efforts to include these effects in computational studies pertaining to CO 2 ER. Based on the results in Figure , we show that there is a significant energy barrier for the formation of the CO pathway intermediate * COOH, whereas * OCHO is expected to form readily on the Ag(110) surface in the presence of * H.