Infrared studies of benzotriazole on copper electrode surfaces - Role of chloride in promoting reversibility

The potential-dependent behaviors of benzotriazole (BTAH) and 1-(methoxymet hyl)-1H-benzotriazole (MeOMe-BTA) on copper surfaces were studied by cyclic voltammetry and in situ polarization modulation infrared reflection absorp tion spectroscopy. The identity of the anion in the supporting electrolyte has a significant effect on the formation and decomposition of the Cu(I)BTA multilayer surface complex. In chloride-containing solution, the Cu(I)BTA film is more easily formed. This film can be completely reduced upon excurs ion to more negative potentials. In sulfuric acid solution, the Cu(I)BTA fi lm is formed less readily at more positive potentials and cannot be complet ely reduced at more negative potentials. The differences in the film format ion/decomposition in the two electrolytes are attributed to coordination of the anion (Cl- or HSO4-) to the Cu(I) center of the Cu(I)BTA complex. Seco ndary ion mass spectrometric results also show that the anion coordination changes the amount of specific elements incorporated into the copper electr odeposit. MeOMe-BTA does not form a complex with copper due to blockage of one of the triazole ring nitrogens, and its electrochemical behavior is not affected by the anion identity. (C) 2001 The Electrochemical Society. [DOI : 10.1149/1.1359202] All rights reserved.