The effect of triethanolamine (TEA) on reduction and oxidation process of copper in 1-hydroxyethylene-1,1-diphosphonic acid (HEDPA) electrolyte was studied. The distribution of cathode current density was checked by using Hull Cell. Electrochemical measurements, such as cyclic voltammetry, electrochemical impedance spectroscopy and potentiodynamic polarization technique, were employed to investigate the electrochemical behavior of copper deposition. The IR spectra of the complex and the absorbance curves of the electrolyte were used to characterize the coordination compounds. The introduction of TEA enhances cathode current density of the HEDPA electrolyte, suppresses electrodeposition of the copper, promotes the dissolution of copper anode, and inhibits the liberation of hydrogen. In the low-TEA-concentration electrolyte, the reduction process of copper at a glassy carbon electrode was controlled by electrochemical mechanism. With increasing the TEA concentration, diffusion mechanism gradually becomes to control the reduction process of copper, meanwhile, an even and compact copper coating for the fine grains was obtained. The introduction of TEA in the HEDPA electrolyte induces formation of the CuTEA(OH)₂ coordination compounds. The formed CuTEA(OH)₂ coordination compounds adsorb on the electrode surface, which influences the electrochemical reaction.

Key words: 1-hydroxyethylene-1,1-diphosphonic acid (HEDPA), triethanolamine (TEA), electrodeposition, copper, IR spectra