REDUCTION OF NO ON AU SINGLE-CRYSTAL ELECTRODES IN ALKALINE-SOLUTION

The electrochemical behavior of nitrogen compounds on Au(lll), Au(100) and Au(110) was investigated in alkaline solution. Each crystal plane was identified by Pb underpotential deposition (UPD) waves in perchloric acid solution. The UPD waves were unchanged after oxidation and reduction of a surface monolayer of Au atoms on the respective electrodes. NO underwent a ''disproportionation'' to NO; and reduced species in the alkaline solution. However, only NO was electrochemically active. Cyclic voltammograms obtained in an alkaline solution containing dissolved NO showed a main reduction peak at ca. 0 V RHE and an oxidation peak at ca. 0.6 V, almost independent of the crystal plane in contrast with the case of PI electrodes. We concluded from the voltammetric study that the former peak is due to the production of NH2OH, and that oxidation of NH2OH remaining near the surface gives the latter peak. The products in the two peaks were identified using in-situ ''one-point touch'' differential electrochemical mass spectroscopy: NH2OH was mainly oxidized to NO; N2H4, which apparently gave the same oxidation peak at ca. 0.6 V, yielded N-2 exclusively.