在离子液体BMImBF4中电沉积光亮金镀层

摘要

在离子液体l-丁基-3-甲基咪唑四氟硼酸盐([BMIm][BF4])中以HAuCl4.3H2O为主盐、通过添加5,5-二甲基乙内酰脲(DMH)和胞嘧啶可得到色泽光亮、厚度达1.5 μm的金镀层,沉积过程中阴极电流效率可达到100％.SEM和XRD测试结果表明,DMH和胞嘧啶具有细化晶粒、平整镀层的作用.电化学测试结果表明,DMH可分别与Au3+、Au+形成配合物[Au(DMH)4]-、[Au(DMH)2]-,抑制了还原过程的表面转化步骤,从而增加了阴极极化,起到光亮镀层、细化晶粒的作用:胞嘧啶可在金核表面吸附,从而可以进一步光亮镀层、细化晶粒,与DMH有协同作用.循环伏安测试研究了镀液的电化学行为,研究表明在此体系中Au3+的还原为两步还原过程,分别为Au3+→Au+和Au+→Au.此外DMH和胞嘧啶的添加不会带来副反应.%A golden-yellow gold deposit with a thickness of 1.5 μm was electrodeposited from the bath with 5,5-dimethylhydantoin (DMH) as the complexing agent and cytosine as the additive in [BMIm][BF4] solution.The cathodic current efficiency was nearly 100％ during electrodepositing.SEM and XRD results indicatd that DMH and cytosine had significant effects on the surface morphologies and phase structure of the deposits.The grain size and roughness of gold deposits decreased adding DMH and cytosine into the bath.Moreover,the Au (111) plane also became more obvious.The influences of DMH and cytosine were studied by the linear sweep voltammetry (LSV).The gold complexes [Au(DMH)4]-,[Au(DMH)2]-can be formed by DMH and Au3+,Au+,and the surface convert process was inhibited in the reduction process.The addition of DMH increased the cathodic polarization,which can brighten gold deposits and refine crystal grains of gold deposits.Cytosine was be absorbed on Au nuclei,and it had synergistic effects with DMH on brightening gold deposits and refining crystal grains.Cyclic voltammetry (CV) was used to investigated the electrochemical behavior and the results revealed that the reduction of Au3+ to Au had a two-step reduction process.The first reduction process was Au3+ to Au+,and the second process was Au+ to Au,and the addition of DMH and cytosine did not bring side reactions.