Sakai Sho-ichiro, Nakanishi Shuji, Nakato Yoshihiro
Division of Chemistry, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan.
J Phys Chem B. 2006 Jun 22;110(24):11944-9. doi: 10.1021/jp061282d.
We have investigated mechanisms of oscillations and formation of nano-scale layered structures in induced co-deposition of some iron-group alloys (Ni-P, Ni-W, and Co-W) that have unique properties and are widely used in industries. Detailed in situ electrochemical quartz crystal microbalance (EQCM) experiments have revealed that the electrodeposition (induced co-deposition) of the alloys has negative differential resistances (NDRs), from which the oscillations and the layer-structure formation arise. The NDRs, however, cannot necessarily be seen in current-potential curves owing to overlap of hydrogen evolution current, indicating that the oscillations are of a hidden-NDR (H-NDR) type. The EQCM experiments have also shown that electrolyte components (such as H2PO2- and WO4(2-)) or related species are adsorbed at the electrode (deposit) surface and act as a promoter for the co-deposition reaction and that the NDRs arise from desorption of the adsorbed promoter. Interestingly, the adsorbed promoter is drawn into the deposition reaction itself, thus resulting in the alloy deposits. This mechanism was supported by in situ EQCM investigations of the oscillation as well as Auger electron spectroscopic (AES) analyses of deposits formed during the oscillation. The present work has for the first time clarified a general mechanism for the induced co-deposition reactions of some industrially important iron-group alloys (Ni-P, Ni-W, and Co-W).
我们研究了某些具有独特性能且在工业中广泛应用的铁族合金（Ni-P、Ni-W和Co-W）诱导共沉积过程中纳米级层状结构的振荡和形成机制。详细的原位电化学石英晶体微天平（EQCM）实验表明，这些合金的电沉积（诱导共沉积）具有负微分电阻（NDR），振荡和层状结构的形成由此产生。然而，由于析氢电流的重叠，在电流-电位曲线中不一定能看到NDR，这表明振荡属于隐藏负微分电阻（H-NDR）类型。EQCM实验还表明，电解质成分（如H2PO2-和WO4(2-)）或相关物种吸附在电极（沉积物）表面，并作为共沉积反应的促进剂，而NDR则源于吸附促进剂的解吸。有趣的是，吸附的促进剂自身参与沉积反应，从而形成合金沉积物。振荡的原位EQCM研究以及振荡过程中形成的沉积物的俄歇电子能谱（AES）分析支持了这一机制。本研究首次阐明了一些工业上重要的铁族合金（Ni-P、Ni-W和Co-W）诱导共沉积反应的一般机制。
