Here we report our findings of the mechanistic differences in the formation of * OCHO and * COOH and their respective interactions with the H 2 production pathways on an Ag(110) surface. We show that there are two major bifurcations in the reaction mechanism before and after formation of * H that control the selectivity between CO, HCOO -and H 2 . We present reaction barrier calculations to show that the formation of * OCHO has a significantly lower kinetic barrier relative to * COOH on Ag(110) and that solvation of the transition state by the surrounding water molecules plays an important role in determining this barrier. Finally, we demonstrate that the influence of lateral adsorbate-adsorbate interactions resulting from the presence of * OCHO on the surface promotes CO production while inhibiting itself and the formation of HCOO -as a consequence.