The electroreduction of nitrobenzene has been studied on Au single crystals of (111), (110), (100), and (210) orientations and on Au polycrystals in dilute aqueous perchlorate solution using cyclic voltammetry. The voltammograms were found to be dependent sensitively on the surface orientation. Notably, the reduction on (110), (210), and (poly) electrodes can lead to a stably adsorbed redox intermediate, not reported before, at about 0.33 V versus SCE and the intermediate is deduced as the phenyldihydroxylamine/phenyldihydroxylamine cation redox couple. The unusual stability of the redox intermediate is found to correlate with the orientation of adsorbed water molecules that can be controlled intimately by the applied potential in relationship to the potential of zero charge on the surfaces.