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 C u specimens in 85% H3PO4 solution at 25-degrees-C was investigated usi ng symmetric square-wave periodic-potential routines. The electrochemi cal characteristics of electrofaceted specimens were followed by Tl up d voltammetry and complemented by scanning electron microscopy observa tions. Depending on the experimental conditions the electrochemical fa ceting involves a preferred crystallographic orientation at the specim en surface and an increase in surface roughness. Electrofaceting at gr ain 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 int erpretation of the overall effect is given in terms of the likely reac tion mechanism already established for the Cu/Cu(II) and Cu/Cu(I) elec trodes, including further kinetic aspects of the Cu(I) disproportionat ion reaction in the solution.