氯离子对ChCl-Urea低共熔溶剂中银电沉积的电化学行为影响

doi:10.13208/j.electrochem.211115

摘要/Abstract

摘要：

以氯化胆碱-尿素低共熔溶剂为基础液,使用循环伏安法、计时电流法、Tafel极化曲线、Gerisher交换电流密度法、扫描电子显微镜以及X射线衍射等方法研究了电沉积银过程中的电沉积机理、电结晶行为,以及NH₄Cl存在下对配合物、相组成以及镀层微观形貌等的影响。结果表明, ChCl-Urea体系中氯离子的加入改变了Ag⁺的还原电位（vs. Ag|AgCl）,镀液中Ag⁺形成了配合物[AgCl_n]^1-ⁿ, 使还原电位发生了负移, 由-0.85 V负移至-0.98 V。通过拟合CA曲线和理论曲线对比发现, Ag(I)在ChCl-Urea DES中的成核方式与氯离子的浓度有关,低浓度下的成核方式具有三维瞬时成核和三维连续成核的混合成核特征,高浓度下的成核方式符合三维瞬时成核。镀液中主要放电络离子是[AgCl₂]^-。电沉积得到的是紧密颗粒球状纯银镀层,氯离子的加入抑制了枝晶状银镀层的生成。

关键词: 氯化胆碱-尿素低共熔溶剂, 银电沉积, 添加剂, 络合物, 电化学行为

Abstract:

Metallic silver coating has been widely used in the fields of microelectronics industry, catalyst, sensor and preparation of magnetoresistive materials because of its excellent corrosion resistance, good lubricity, high conductivity, excellent decoration and high catalysis. Compared with the traditional aqueous solution system, the research on metal electrodeposition in ionic liquid system is developing rapidly. In addition, additives are the key factors in the silver plating process. Adding a small amount of organic or inorganic additives to the plating solution will significantly change the coating properties, such as improving brightness, hardness and ductility. In this paper, using choline chloride urea (ChCl-Urea) low eutectic solvents (DESs) as the base solution, cyclic voltammetry (CV), chronoamperometry (CA), Tafel polarization and other electrochemical methods were used. The effect of chloride ion on the electrochemical behavior of silver electrodeposition was deeply studied. The phase composition and micro morphology of the silver coating were also studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The existing forms and main discharge complexes in the presence of NH₄Cl in the plating solution were studied by the classical gerisher exchange current density method. The results showed that the addition of chloride ion in ChCl-Urea system changed the reduction potential of Ag⁺ (vs. Ag|AgCl), and Ag⁺ in the plating solution formed complex [AgCl_n]^1-ⁿ, which makes the reduction potential shift negatively from -0.85 V to -0.98 V. The increase of overpotential was conducive to the formation of silver coating with good performance. By comparing the fitting CA curve with the theoretical curve, it is found that the nucleation mode of Ag(I) in ChCl-Urea DES was related to the concentration of chloride ion. The nucleation mode at low concentration had the mixed nucleation characteristics of three-dimensional instantaneous nucleation and three-dimensional continuous nucleation, and the nucleation mode at high concentration conformed to three-dimensional instantaneous nucleation. The results of gerisher exchange current density analysis revealed that the main discharge complex ion in the plating solution was [AgCl₂]^-. The addition of chloride ion inhibited the formation of dendritic silver coating. At the same time, this paper provides a method for preparing compact spherical pure silver coating. As means of preparing nanospherical silver, electroplating is the main direction of future research. Basic research on relevant additives is also essential. In the process of silver plating, the action mechanism of additives needs to be further studied. This plays an important guiding role in the development of electroplating additives and electroplating process.

Key words: choline chloride-urea deep eutectic solvent, silver electrodeposition, additive, complex compound, electrochemical behavior

战充波, 张润佳, 付旭, 孙海静, 周欣, 王保杰, 孙杰. 氯离子对ChCl-Urea低共熔溶剂中银电沉积的电化学行为影响[J]. 电化学（中英文）, 2022, 28(5): 2111151.

Chong-Bo Zhan, Run-Jia Zhang, Xu Fu, Hai-Jing Sun, Xin Zhou, Bao-Jie Wang, Jie Sun. Effect of Chloride Ion on Electrochemical Behavior of Silver Electrodeposition in ChCl-Urea Low Eutectic Solvent[J]. Journal of Electrochemistry, 2022, 28(5): 2111151.

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NH₄Cl (mol·L^-1)	lgi₀ (A·cm^-2)	B_c (V)
0.1	-2.189	0.776
0.3	-2.331	0.807
0.6	-2.515	0.788