An ex situ and operando analysis of thiourea consumption and activity during a simulated copper electrorefining process

Electroreduction is an essential electrochemical technique, applied in many industries. The process can be used to produce coatings, circuit boards, to refine metals, etc. Electroreduction during plating or refining is assisted by organic or inorganic additives present in the electrolyte, with the aim to produce smooth metal deposits. A complex component of most additive mixtures in copper refining is thiourea. This work applies a coupled approach to study the time dependent characteristics of thiourea in a copper plating solution. Operando Odd Random Phase Electrochemical Impedance Spectroscopy (ORP-EIS) is used to study the electrochemical behavior of the plating solution during the process of plating while the concentration of thiourea is determined using ion chromatography. The combination of these techniques allows an in-depth study of the plating process, describing the additive behavior in the bulk electrolyte and the additive impact on the cathode plating process.