THE ELECTROCHEMICAL FACETING OF COPPER IN 85-PERCENT AQUEOUS O-PHOSPHORIC ACID BY USING A POTENTIAL REVERSAL TECHNIQUE

The electrochemical faceting of differently prepared polycrystalline Cu specimens in 85% H3PO4 solution at 25-degrees-C was investigated using symmetric square-wave periodic-potential routines. The electrochemical characteristics of electrofaceted specimens were followed by Tl upd voltammetry and complemented by scanning electron microscopy observations. Depending on the experimental conditions the electrochemical faceting involves a preferred crystallographic orientation at the specimen surface and an increase in surface roughness. Electrofaceting at grain domains without a significant increase in surface roughness occurs preferentially at high frequencies, whereas Cu islands with a marked increase in surface roughness are produced at low frequencies. The interpretation of the overall effect is given in terms of the likely reaction mechanism already established for the Cu/Cu(II) and Cu/Cu(I) electrodes, including further kinetic aspects of the Cu(I) disproportionation reaction in the solution.