The mechanism of electrolytic metal deposition
The mechanism of electrolytic metal deposition
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电解金属沉积的机理
DOI：
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发表时间：
1958
期刊：
影响因子：
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通讯作者：
J. Bockris
中科院分区：
文献类型：
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作者：
B. Conway;J. Bockris
从铜，镍和银离子的水溶液中的电解金属沉积的可能机制进行检查，通过推导和比较相关的势能曲线的目的，指示速率决定步骤。在整体反应中的以下步骤被认为是：从溶液的离子转移到表面网站，表面扩散的吸附离子，连续脱水的adions在晶格建设网站。在中间步骤中形成的adions和adatoms的区别，它表明，中性adatom的形成是不可能的。离子从溶液转移到金属表面的活化热（H2O）取决于转移发生的位置，平面位置的活化热明显小于其他位置的活化热（例如：G.边缘、扭结等）。形成吸附原子的转移具有高得令人望而却步的H2O值。晶格构建是通过转移的离子向边缘或扭结的表面扩散来完成的。在沉积过程的每一个连续阶段，离子或二离子的水合作用发生变化，并对沉积的机理和过程产生重要影响。二价离子直接沉积到表面位点上被证明与高活化热和低电化学速率常数相关，如实验发现的Ni 2+，Fe 2+和Co 2+沉积。当沉积反应可以通过涉及稳定离子的中间氧化还原步骤发生时，G.在铜的情况下，显示出与在一个步骤中发生二价离子的沉积相比，可以产生更低的活化自由能。这与铜沉积的实验行为一致。在低过电位，它示出的离子转移和表面扩散的步骤将具有可比的速率常数的情况下，铜和银沉积，而在较高的过电位，铜2+离子的还原成为速率决定在铜，而Ag+离子的离子转移成为速率决定在银。这与实验观察到的行为一致。
Possible mechanisms of electrolytic metal deposition from aqueous solutions of cupric, nickelous and silver ions are examined by deriving and comparing the relevant potential energy profiles with the purpose of indicating the rate-determining step. The following steps in the overall reaction are considered: ionic transfer from the solution to surface sites; surface diffusion of adsorbed ions; successive dehydration of the adions at lattice building sites. The formation of adions and adatoms in intermediate steps is distinguished and it is shown that neutral adatom formation is unlikely. The heat of activation (∆H0‡) for transfer of ions from the solution to the metal surface, depends upon the site to which transfer occurs, that to a planar site being significantly less than that to other sites (e. g. edges, kinks, etc.). Transfer to form adatoms has prohibitively high ∆H0‡ values. Lattice building is accomplished by surface diffusion of transferred adions to edges or kinks. At each of the consecutive stages of the deposition process, a change in hydration of the ion or adion occurs and has important effects on the mechanism and kinging of deposition. Direct deposition of divalent ions on to surface sites is shown to be associated with high heats of activation and low electrochemical rate constants as found experimentally for Ni2+, Fe2+ and Co2+ deposition. When the deposition reaction can occur through an intermediate redox step involving a stable ion as, e. g. in the case of copper, it is shown that lower free energies of activation can result than if the deposition of the divalent ion occurs in one step. This is consistent with the experimental behaviour found for copper deposition. At low overpotentials, it is shown that both the steps of ionic transfer and surface diffusion would have comparable rate constants in the case of copper and silver deposition whilst at higher overpotentials, the reduction of Cu2+ ions becomes rate determining at copper, whilst ionic transfer of Ag+ ions becomes rate determining at silver. This is in agreement with the behaviour observed experimentally.