Thermoconvection-enhanced deposition of copper

Thermal gradients and thermoconvective flow in the vicinity of the electrode are shown to enhance transport of the electroactive species during reduction of copper. The transport-limited current of the Cu reduction reaction is more than doubled under conditions of positive and negative thermal gradient in comparison with isothermal conditions. Futhermore, thermal gradients affect strongly the potential dependence of the current. Kinetic and thermodynamic parameters for electrodeposition of copper were determined from polarization curves analyzed with Butler-Volmer, Tafel, and Levich expressions. Under isothermal conditions the exchange current density for the Cu reduction reaction was found to be given by log i sub 0 =7.95 - 2690T exp -1 (i sub 0 in mA cm exp -2 and T in K) under conditions of 10 mM CuSO sub 4 in 2 M H sub 2 SO sub 4 (10 < =T/ deg C < =80). The diffusion coefficient of Cu(II) at 298 K under the same conditions was found to be 5.36mult10 exp -6 cm exp 2 s exp -1 . Decrease of the effective thickness of the diffusion layer due to thermoconvection in the vicinity of the cathode is responsible for the effect of the gradient on transport-limted current.