Effect of Halide Ions on Electrodeposition Behavior and Morphology of Electrolytic Copper Powder

To investigate the effect of halide ions on the electrodeposition behavior and morphology of copper powder, polarization curves were measured and constant current electrolysis of 300 and 500 A·m−2 was conducted in an electrolytic solution containing 0.079 mol·dm−3 Cu2+ and 0.5 mol·dm−3 free H2SO4 at 293 and 303 K without stirring. Cl− promoted the deposition of copper powder, while Br− and I− suppressed deposition. The current efficiency for copper deposition increased with the addition of Cl− and decreased with the addition of Br−. The addition of Cl− reduced the average particle size of the copper powder and caused the dendrite-shaped branches and trunks to grow thinner and longer, resulting in a lower tap density. In contrast, the addition of Br− caused the average particle size, average crystallite size, and tap density of the copper powder to decrease. With increasing Cl− concentration, the current efficiency for copper deposition increased, that is, copper deposition was promoted. This even occurred in the region in which Cu2+ ion diffusion was the rate-determining process, indicating that the deposition of copper powder was affected by the charge-transfer process. The change in the morphology of the copper powder with the addition of halide ions is attributed to the change in the charge-transfer process. The deposition of copper powder appears to proceed under a mixed rate-determining process involving the diffusion of Cu2+ ions and charge transfer.