添加剂甲基紫-Cl^(-)作用下铜的快速电结晶过程

Fast electrocrystallization of copper in presence of additive methyl violet and Cl^(-)

采用线性电势扫描、循环伏安和计时电流等电化学方法研究40℃下甲基紫和Clˉ单独存在与同时存在时,含315 g/L CuSO4、110 g/L H2SO4的高浓度酸铜溶液中Cu在铜电极上的电结晶过程。结果表明:甲基紫和Clˉ单独存在或同时存在时Cu的电结晶过程较为复杂,开始先按瞬时成核三维生长方式进行;随着时间的延长,逐渐向连续成核三维生长方式进行,但当成核时间较长时,其电结晶成核偏离理论模型,表现出扩散与电化学反应混合控制,而且甲基紫和Clˉ共同作用时更快进入混合控制。甲基紫和Clˉ在电沉积过程表现出显著的去极化作用,且它们的共同作用使Cu2+的扩散系数增大,明显促进铜的快速电结晶和成核过程。适宜的甲基紫和Clˉ浓度,例如2.5 mg/L甲基紫和20 mg/L Clˉ,会增大Cu2+的扩散系数,同时获得足够大的成核数密度,对铜电结晶有利。

The copper electrocrystallizations on copper electrode in the concentrated acid CuSO4 solutions,containing 315 g/L CuSO4 and 110 g/L H2SO4 with methyl violet and Clˉ alone or both of them at 40 ℃ were studied by linear sweep voltammetry,cyclic voltammetry and chronoamperometry techniques.The results show that the electrocrystallizations in the electrolytes above are complex relatively.At beginning,the electrocrystallization processes follows the instantaneous nucleation with three-dimensional growth,and then changes to the progressive nucleation with three-dimensional growth gradually.But the processes would deviate from the theoretical model after longer nucleation time.The deviation suggests that the processes are controlled by both diffusion and electrochemical reaction step.Moreover,the combination of methyl violet and Clˉ enable electrocrystallization to run into mixed control faster than methyl violet or Clˉ.The methyl violet and Clˉ have significant depolarization effect in the processes,and increase the diffusion coefficient of Cu2＋ in the electrolytes cooperatively and facilitate the electrocrystallization and nucleate process of copper notably.An optimum concentration of both methyl violet and Clˉ,such as 2.5 mg/L methyl violet and 20 mg/L Clˉ,can increase the diffusion coefficient and get enough nuclear number density on the electrode surface and is beneficial to electrocrystallization.