[目的]研究氯化胆碱与乙二醇物质的量比为 1∶3 的低共熔溶剂(用ChCl-3EG表示)中Sn(Ⅱ)电沉积的电化学行为及所得Sn镀层的耐蚀性,并将测试结果与氯化胆碱与乙二醇物质的量比为 1∶2 的体系(用ChCl-2EG表示)进行对比.[方法]先通过循环伏安法研究了Sn(Ⅱ)在ChCl-3EG体系中的电化学还原过程,研究了温度和主盐浓度对其电化学行为的影响.采用计时电流法研究了该体系中锡的形核生长机理,通过塔菲尔极化曲线测试研究了所得Sn镀层的耐蚀性,使用扫描电镜分析了Sn镀层的微观形貌.[结果]Sn(Ⅱ)在ChCl-3EG体系中的电化学还原是受扩散控制的不可逆过程.Sn(Ⅱ)在60 ℃的ChCl-3EG体系中的扩散系数为1.22×10-6 cm2/s,与在ChCl-2EG体系中的扩散系数接近,但前者的扩散活化能明显更低.Sn(Ⅱ)的电结晶过程为三维瞬时形核,适当增大阴极电流密度有利于提高 Sn 镀层的耐蚀性.[结论]Sn(Ⅱ)在物质的量比为1∶3的氯化胆碱-乙二醇体系中更容易还原,能耗更低,得到的Sn镀层具有优异的耐蚀性,可作为电沉积或电解精炼锡的电解液.
Electrochemical behavior of tin electrodeposition in choline chloride-ethylene glycol deep eutectic solvent
[Introduction]The electrochemical behavior during electrodeposition of Sn(Ⅱ)in a deep eutectic solvent(DES)comprising choline chloride and ethylene glycol at a molar ratio of 1:3(coded as ChCl-3EG),as well as the corrosion resistance of Sn coating electrodeposited therefrom were studied.The experimental results were also compared with those measured in a deep eutectic solvent comprising choline chloride and ethylene glycol at a molar ratio of 1:2(coded as ChCl-2EG).[Method]The electrochemical reduction process of Sn(Ⅱ)ions in ChCl-3EG and the effects of temperature and SnCl2·2H2O concentration on the electrochemical behavior of Sn(Ⅱ)were studied by cyclic voltammetry.The nucleation and growth mechanisms of tin in ChCl-3EG were investigated by chronoamperometry.The corrosion resistance of Sn coating was analyzed by Tafel polarization curve measurement.The morphology of Sn coating was characterized by scanning electron microscopy.[Result]The electrochemical reduction of tin in ChCl-3EG was a diffusion-controlled irreversible process.The diffusion coefficient of Sn(Ⅱ)in ChCl-3EG was estimated to be 1.22×10-6 cm2/s at 60℃,which is close to that in ChCl-2EG,while the diffusion activation energy of the former was much lower than the latter.The electrocrystallization of Sn(Ⅱ)in ChCl-3EG showed the nature of three-dimensional instantaneous nucleation.A suitable increase of cathodic current density during the electrodeposition of Sn(Ⅱ)is favorable for the improvement of the corrosion resistance of Sn coating.[Conclusion]The ChCl-3EG deep eutectic solvent can be applied as an electrolyte for electrodeposition or electrolytic refining of tin,due to the fact that the reduction of Sn(Ⅱ)in ChCl-3EG is more easy with relatively low energy consumption,and the electrodeposited Sn coating features good corrosion resistance.
choline chloride-ethylene glycol deep eutectic solventstinelectrodepositionnucleation mechanismcorrosion resistance
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