Action d'oxydations et de réductions électrochimiques successives sur la structure superficielle d'électrodes d'or polycristallines: Étude optique et életrochimique

Abstract

Flat, mechanically polished gold electrodes have been subjected to several hundred cycles of electrochemical oxidation and reduction (0.4 to 1.9 V NHE) in normal sulfuric acid. The evolution of these electrodes has been followed by electrochemical measurements (capacity and potentiokinetic curves) and optical (ellipsometry) measurements, and the surfaces have been examined by metallographic microscopy. After a number of cycles the electrochemical treatment transforms the originally disturbed surface into a structured surface, with appearance of grain boundaries and faceting analogous to thermal faceting. Considering the work of Vetter and Schultze, we interpret the restructuring of the electrode surface as being due to two facts: mobility of metal atoms, because of their delocalization during the oxygen desorption phase and the anisotropy of the surface energy, owing to the presence of adsorbed oxygen. The complex evolution of the optical properties of the metal cannot be accounted for simply by facetting, and thus we have been led to postulate an accumulation in the metal of traces of undesorbed oxygen.