As the potential was slowly shifted more and more negative, several features were noted (Fig. ). There was a broad negative peak increasing in intensity centered around 1350 cm -1 , well matching that of NO3 - (Fig. ) and is attributed to its depletion. However, this was convoluted with a positive band arising at 1374 cm -1 , attributed to surface adsorbed *NO3. A positive band at 1255 cm -1 is attributed to *NO2 -and the positive band at 1191 cm 1 is attributed to NH2OH. The presence of NH2OH indicates that the reaction at least partially proceeds through the *NO → *NHO → *NH2O → *NH2OH → *NH3 pathway. Note that the particular surface binding motif (singly bound or multiply bound intermediates) is not distinguished here. Finally, the band at 1101 cm -1 comes from the NH3 product. The assignment of *NO3 is bolstered by the redshift of this band when using 15 NO3 -as the reactant but not when using D2O as the solvent (Fig ).