LiCl-KCl熔盐中Zr(Ⅳ)于Mo电极上的电化学行为

摘要

通过循环伏安法、方波伏安法和计时电位法等研究了 LiCl-KCl 共晶熔盐中 ZrCl4于 Mo 电极上的电化学行为.探究Zr(Ⅳ)于 Mo阴极的还原机理,并计算 Zr(Ⅱ)的扩散系数及 Zr(Ⅱ)/Zr(0)的表观标准电势.结果表明:Zr(Ⅳ)在 Mo阴极还原机理为:Zr(Ⅳ)+2 e=Zr(Ⅱ);Zr(Ⅱ)+2 e=Zr(0)或 Zr(Ⅱ)+e+Cl-=ZrCl;ZrCl+e=Zr(0)+Cl-;金属 Zr 在阳极的氧化过程为:Zr(0)-2 e=Zr(Ⅱ)和 Zr(Ⅱ)-2 e=Zr(Ⅳ).Zr(Ⅳ)还原为Zr(Ⅱ)和 Zr(Ⅱ)还原为 Zr(0)均为可逆反应,且还原过程均为扩散控制.LiCl-KCl 熔盐中Zr(Ⅱ)于 Mo阴极上的扩散系数与温度的关系为:ln D=-6724/T-2.95,扩散的活化能Ea=55.9 kJ/mol.Zr(Ⅱ)/Zr(0)的表观标准电位与温度的关系为:E☉?Zr(Ⅱ)/Zr(0)=-2.695+9.33×10-4T.%In this presentation,the electrochemical behaviors of ZrCl4on the Mo electrode in the LiCl-KCl molten salt have been investigated by various techniques,including cyclic volta-mmetry,square wave voltammetry,and chronopotentiometry etc.The reduction mechanism of Zr(Ⅳ)on the Mo electrode has been discussed,and the diffusion coefficient of Zr(Ⅱ)and the apparent standard potential of Zr(Ⅱ)/Zr(0)have been calculated.The results show that the reduction mechanism of Zr(Ⅳ)on the Mo cathode is that Zr(Ⅳ)+2e=Zr(Ⅱ);Zr(Ⅱ)+2e=Zr(0)or Zr(Ⅱ)+e+Cl-=ZrCl;ZrCl+e=Zr(0)+Cl-,and the oxidation process of Zr on the anode is:Zr(0)-2e=Zr(Ⅱ)and Zr(Ⅱ)-2e=Zr(Ⅳ).The CV of LiCl-KCl-ZrCl4 indicate that the reduction process Zr(Ⅱ)/Zr(0)is reversible and controlled by diffusion. The dependence of diffusion coefficients of Zr(Ⅱ)in the LiCl-KCl molten salt with tempera-ture is ln D=-6 724/T-2.95 and the activation energy is Ea=55.9 kJ/mol.The relation-ship of apparent standard potential of Zr(Ⅱ)/Zr(0)is E☉?Zr(Ⅱ)/Zr(0)= -2.695+9.33×10-4T.