The surface coordination chemistry of benzotriazole (BTAH) at copper electrode was investigated by in situ electrochemical surface enhanced Raman spectroscopy (SERS) and electrochemical synthesis in the acetonitrile solution for the first time. The surface coordination processes were researched and the surface complexes prepared by electrochemical method were characterized by microanalysis, X-ray crystallographic determination and Raman spectroscopy. The influence of the neutral ligand of triphenylphosphine (pph₃) on the adsorption and film formation process of BTAH was investigated. In situ SERS studies revealed that BTAH underwent three processes of chemical adsorption, formation of compact polymer layer and the breaking of the polymer layer due to the oxidation of copper on the surface, in which the compact polymer layer inhibited the dissolution and oxidation of copper effectively. With the introduction of pph₃ into the solution, the formation of surface polymer complex film was suppressed because of the existence of the soluble cation. The formation of complex of Cu(pph₃)_n⁺ with BTA^－ in the solution resulted in a significant increase of the dissolution of copper. The microanalysis and X-ray crystal measurements indicated its structure of Cu₅(BTA)₅(pph₃)₄Cl•2CH₃CN.

Key words: copper; surface-enhanced Raman spectroscopy, electrochemical synthesis, benzotriazole, adsorption