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, the polarization curves were measured and constant current electrolysis of 300 Am-2 and 500 Am-2 was conducted in an electrolytic solution of 0.079 moldm-3 of Cu2+ and 0.5 moldm-3 of free H2SO4 at 293K and 303K without stirring. In the deposition of copper powder, Cl- had a promoting effect on the deposition of copper powder, while Br- and I- had a suppressing effect. The current efficiency for Cu deposition increased with the addition of Cl- and decreased with Br-. The addition of Cl- reduced the average particle size of the copper powder and grown dendrite-shaped branches and trunks, resulting in a lower tap density. On the other hand, when Br- was added, the average particle size and crystallite size of the copper powder became smaller, and the tap density also became smaller. With increasing Cl- concentration in solution, the current efficiency for Cu deposition increased, that is, copper deposition was promoted even in the diffusion rate-determining region of Cu2+ ions, showing that the deposition of copper powder was affected by the charge transfer process for Cu deposition. The change in morphology of Cu powder with halide ions is attributed to change of the charge transfer process. The deposition of Cu powder seems to proceed under a mixed rate-determining process of the diffusion of Cu2+ ions and charge transfer. © 2021 The Japan Institute of Metals and Materials.