Effect of Additives on the Direct Electrodeposition of Copper From Acid Solution Containing 20 g/L Copper(II)

The effect of 3-mercapto-l-propanesulfonate sodium salt (MPS), polyethylene glycol (PEG), thiourea (TU) and ethylenethiourea (ETU) on copper electrodeposition from acidic sulfate electrolyte with low Cu2+ concentration was investigated by linear sweep voltammetry (LSV), and chronoamperometric and electrochemical impedance spectroscopy (EIS) measurements. The LSV experimental results showed that all additives have inhibitory effects on copper electrodeposition. The results of the chronoamperometric experiments suggested that copper electrodeposition was related to three-dimensional instantaneous nucleation in the diffusion-controlled regime regardless of the presence of the additives. In agreement with the LSV results, EIS experiments revealed the influence of the additives on the electric double layer during the electrodeposition process. MPS and PEG were found to inhibit the electrodeposition of copper through direct adsorption on the cathode surface, while TU and ETU produce stronger inhibition through complex intermediate reactions. Scanning electron microscopy images showed that the addition of TU and ETU resulted in flatter and finer-grained copper electrodeposits. TU and its derivatives are considered to be suitable additives for direct copper electrodeposition at low copper ion concentration.

Automated summary

The study investigated the effects of MPS, PEG, TU and ETU on copper electrodeposition and found that the additives have inhibitory effects on the process. MPS and PEG inhibit copper deposition through direct adsorption on the cathode surface, while TU and ETU inhibit it through complex intermediate reactions, resulting in flatter and finer-grained deposits. These findings suggest that TU and its derivatives are suitable additives for direct copper electrodeposition at low copper ion concentration.