The influence of sodium 3-mercaptopropanesulfonate (MPS) with different concentrations on the copper electrodeposition on a glass carbon electrode (GCE) from CuSO₄-H₂SO₄ electrolytes was studied by using cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CA), AC impedance and scanning electron microscopy (SEM) techniques. The experiment results of CV, LSV and AC impedance indicated that MPS inhibited copper electrodeposition. The inhibition effect became strong with the increase of MPS concentration. However, it was found that MPS accelerated the electrocrystallization process of copper. The results of CA and SEM demonstrated that copper electrocrystallization from the electrolytes either with or without MPS followed instantaneous nucleation with three-dimensional growth. And the nuclear number density increased with the increase of the concentration of MPS.

Key words: MPS, copper, electrodeposition, electrocrystallization