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电化学(中英文) ›› 2020, Vol. 26 ›› Issue (6): 859-867.  doi: 10.13208/j.electrochem.191009

• 研究论文 • 上一篇    下一篇

离子液体中18-冠醚-6添加剂对三价铬电沉积的影响

王怡捷, 钮东方, 张新胜*()   

  1. 华东理工大学化学工程联合国家重点实验室,上海 200030
  • 收稿日期:2019-10-15 修回日期:2020-02-27 出版日期:2020-12-28 发布日期:2020-12-28
  • 通讯作者: 张新胜 E-mail:xszhang@ecust.edu.cn

Effect of 18-Crown-6 Additive on Chromium Electrodeposition in Ionic Liquid

WANG Yi-jie, NIU Dong-fang, ZHANG Xin-sheng*()   

  1. State Key Laboratory of Chemical Engineering, East China University of Science and Technology,Shanghai 200030, China
  • Received:2019-10-15 Revised:2020-02-27 Published:2020-12-28 Online:2020-12-28
  • Contact: ZHANG Xin-sheng E-mail:xszhang@ecust.edu.cn

摘要:

在1-丁基-3-甲基咪唑硫酸氢盐([BMIM]HSO4)电镀液中,探究了18-冠醚-6添加剂对电沉积铬的影响. 紫外-可见光谱结果表明,18-冠醚-6与Cr3+形成配合物,使最大吸收波长发生红移. 循环伏安研究表明,Cr3+的还原经历了两步. 18-冠醚-6的添加使Cr3+的峰电位和起始还原电位均正移了220 mV. 能谱仪(EDS)结果显示,在18-冠醚-6的作用下镀层中铬含量有所提高. 铬镀层的扫描电子显微镜(SEM)表征结果表明,加入18-冠醚-6后,所得镀层的颗粒变大. 18-Crown-6/CrCl3/[BMIM]HSO4/H2O电镀液中工艺优化的结果为:在温度为50 oC、pH值为3.5、电流密度为1200 A·m-2、电镀时间为1.5 h的最佳工艺条件下,铬镀层的厚度达到72.5 μm,电流效率为42.3%.

关键词: 三价铬, 1-丁基-3-甲基咪唑硫酸氢盐, 18-冠醚-6, 铬镀层, 电流效率

Abstract:

Trivalent chromium ion (Cr3+) is used for electrodeposition due to its low toxicity. Electrodeposition in ionic liquids can greatly solve for hydrogen evolution problem. However,as a widely used Cr(III) precursor, chromium chloride hydrate (CrCl3·6H2O), still contains water. In the presence of water, Cr3+ will form a complex coordination structure with water molecules ([Cr(H2O)6]3+), which is a stable octahedral structure and is difficult to be directly reduced to chromium metal. Therefore, coordination agents should be added into the bath. In this work, the effect of 18-Crown-6 additive on chromium electrodeposition was investigated in CrCl3/[BMIM]HSO4/H2O plating solution. The UV-Vis spectra showed that 18-Crown-6 formed a complex with Cr3+, destroyed the stable coordination structure formed by Cr3+ and water molecules, making a red shift in the maximum absorption wavelength. The cyclic voltammograms indicated that the electroreduction of Cr3+ occurred in a two-step process, namely, Cr3+ + e → Cr2+ and Cr2+ + 2e → Cr0. Both of the peak potential and initial reduction potential of Cr3+ had positive shifts by 220 mV after adding 18-Crown-6. The reason for this phenomenon was that when 18-Crown-6 was added to the plating solution, the stable structure of [Cr(H2O)6]3+ was destroyed, Cr3+ became more readily to be reduced, thereby, lowered the reduction potential of Cr3+. The EDS data showed that the chromium content in the coating was increased under the action of 18-Crown-6. The improvement indicated that 18-Crown-6 was beneficial to the chromium electrodeposition. The SEM characterizations indicated that the coating obtained in 18-Crown-6/CrCl3/[BMIM]HSO4/H2O plating solution had a larger particle size. Tafel curves suggested that the corrosion resistance of chromium coating was better than that of brass substrate. The optimized process in 18-Crown-6/CrCl3/[BMIM]HSO4/H2O plating solution could be proceeded at the temperature of 50 oC, pH of 3.5, current density of 1200 A·m-2, and plating time of 1.5 h. The thickness of the chrome plating reached 72.5 μm and the current efficiency was 42.3%.

Key words: trivalent chromium, 1-butyl-3-methyl imidazole sulfate, 18-Crown-6, chromium electrodeposition, current efficiency

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