In those previous studies, the general trend is that Cu-In and Cu-Sn catalysts with low In and Sn contents (Curich catalysts) are CO-selective, while those with high Sn and In contents (Cu-poor catalysts) showed a higher tendency toward HCOO -. A variety of mechanistic hypotheses, such as alloying and electronic effects, have been proposed to explain these bimetallic synergetic effects, mostly centered around the crucial role of Cu-In and Cu-Sn interfaces in tuning the binding strength of the key intermediates (e.g., *COOH, *OCHO and *H) and consequently, CO and HCOO -selectivity. For instance, DFT calculations attribute the selectivity shifts (f rom CO to f ormate) with increasing of In or Sn contents to the gradual weakening of the adsorbed *COOH intermediate (which leads to CO), concurrently with enhancing the adsorption of *OCHO intermediate (resulting in HCOO -). A plausible explanation of this observed shif t f rom carbophilic (*COOH, C-bound) to oxophilic (*OCHO, O-bound) adsorption modes could be the charge transfer from Sn or In to Cu sites resulting in localized positive charge regions. These regions on the catalyst surface hamper the adsorption of *COOH intermediate and hence increases the competitiveness of the HCOO -production pathway at the expense of the CO f ormation pathway. These theoretical investigations on Cu-In and Cu-Sn suggest a direct correlation between the surf ace atomic environment (surf ace composition) and the surf ace electronic properties (charge distribution) and indicate their essential inextricable role to the binding energy of the key intermediates for CO and HCOO - production.