Abstract:

The anodic dissolution and cathodic deposition of Cu and effect of allyl thiourea on the processes in acidic media were investigated by using cyclic voltammetry and EQCM. The experimental results demonstrated that there is only one current peak in the anodic dissolution and cathodic deposition of Cu, the M/n value of which is 32.0 and 34.2 g/mol, respectively, showing that the anodic dissolution and cathodic deposition of Cu correspond to the two-electron processes. No Cu⁺ ions, adsorbed Cu(Ⅰ) species or intermediate Cu⁺ was evidenced by in situ EQCM measurements, allyl thiourea may change the mechanism of the anodic dissolution and cathodic deposition of Cu. The M/n values of the anodic dissolution and cathodic deposition of Cu in the presence of allyl thiourea are 61.9 and 65.4 g/mol, respectively, indicating the one-electron processes and producing Cu(Ⅰ) species. The mechanism of the anodic dissolution and cathodic deposition of Cu can be considered as: AT(solution)=AT(suface); Cu=Cu⁺(solution)+e; Cu⁺+AT=(CuAT)⁺(solution). The EQCM studies provided quantitative results of surface mass changes during cathodic deposition and anodic dissolution of Cu, and threw a new light in the elucidating electrodeposition and anodic dissolution of Cu.

Key words: Copper, Electrochemical quartz crystal microbalance, Electro deposition, Anodic dissolution, Allyl thiourea