for HCOOH formation (see 5), pathway 3 is the lowest-energy pathway on Au by rougly 0.2 eV, and is the lowest pathway from *COOH for Ag. This would explain Ag and Au's predilection for making CO using simulations, in agreement with experimental results. This has to our knowledge not been shown directly before with DFT calculations. However, this only gives us one piece of the puzzle, since HCOO** is still more stable than *COOH on Ag and Au (see Fig. ), and also forms more readily from CO 2 (see SI Section "Direct Reaction Pathway Results"). As such, an explanation of how monodentate *COOH or HCOO* occurs on the Ag/Au surface could be the missing link. Note that we also attempted the water-assisted shuttling mechanism for Pb and other HCOOH-producing metals. This pathway was however found unviable under all permutations and conformations, as the distance between the surface, the *H, and the H 2 O was too large for the mechanism to occur, because of the adsorption energies of the species and the larger lattice constant of HCOOH-producing metals (see Fig. ). Instead, *H adsorps directly to the intermediate.