To rationalize the experimental observations on Pt above, we applied DFT to study the competition between the mixed electrochemical & chemical reaction path toward lactic acid and purely electrochemical (EC) pathways to the other products. We have simulated the Pt nanoparticle surfaces on the most stable (111) facet. As shown in the free energy diagram in Fig. , we find that on a Pt (111) surface at 0.5 V vs.