1-丁基-3-甲基咪唑醋酸盐和水组成的混合电解液中三价铬电沉积铬的研究

本文在BMIM]OAc-H₂O电解液中研究了Cr³⁺的电沉积反应. 经循环伏安研究表明,Cr³⁺的还原属于受扩散控制的分步还原过程, 即Cr³⁺ + e →Cr²⁺和Cr²⁺ + 2e → Cr⁰. 在40℃下通过Rendle-Sevcik方程计算得到Cr³⁺的扩散系数为1.2×10^-8 cm²/s. 采用计时电流法探讨了Cr的三维瞬时成核机理. 对沉积的铬镀层进行了XRD、SEM表征, 结果表明经600℃氩气保护下煅烧后的镀层由Cr和Cr₂O₃纳米球状颗粒聚集而成, 其平均粒径为0.48μm. 对40℃，-3.0V条件下所得镀层进行EDX检测，发现Cr与O的能级峰十分明显，其中Cr的质量分数为83.8%. 通过在BMIM]OAc、BMIM]BF₄和BMIM]PF₆三种离子液体体系中电镀得到的Cr镀层质量的比较, 表明OAc-的确有利于Cr的电沉积.

Electrochemical Deposition of Cr fromCr3+ in the Mixed Electrolyte of [BMIM]OAc/H2O

The electrochemical reduction of trivalent chromium ion (Cr³⁺) to Cr in 1-butyl-3-methylimidazolium acetate (BMIM]OAc)-H₂O mixed electrolyte was investigated. The cyclic voltammograms showed that the electroreduction of Cr³⁺ in the mixed electrolyte occurred in a two-step process, namely, Cr³⁺ + e → Cr²⁺ and Cr²⁺ + 2e→ Cr⁰, controlled by the diffusion of Cr³⁺ to the electrode. The diffusion coefficient of Cr³⁺ was 1.2×10^-8 cm²/s at 40 ℃ obtained by Rendle-Sevcik equation. The chronoamperomograms of the Cr³⁺ electrodeposition confirmed the three-dimensional instantaneous nucleation mechanism of Cr. The XRD and SEM characterizations on the Cr coating after calcining in argon atmosphere at 600℃ revealed that the coating was composed of Cr and chromium oxide (Cr₂O₃) nanoparticles with an average particle size of 0.48 μm. The elements of Cr and O were obviously detected from the coating obtained at 40℃ and -3.0V by EDX and the mass fraction of Cr reached 83.8%. Comparison in the qualities of coating layers prepared by Cr electrodepositions in BMIM]OAc, BMIM]BF₄ and BMIM]PF₆ electrolytes indicated that the OAc^- was presented in favor of Cr³⁺ reduction.