As an additional example, we constructed free energy diagrams of two representative pathways on Pt (111); "GM 1-1" mechanism with the most facile N-N coupling step among Tpath (Figure ) and "Distal" mechanism with the lowest UL among E-path (Figure ). The calculated UL for those pathways are 0.45 V and 0.50 V, respectively, suggesting that the former is thermodynamically more favorable. Since the thermochemical coupling barrier (1.2 eV) in GM 1-1 mechanism is larger and potential-independent, while the electrochemical counterpart in