LiCl-KCl-LaCl_(3)熔盐体系中La^(3+)的反应动力学机理  

Kinetic Mechanism of La^(3+) Reaction in LiCl-KCl-LaCl_(3) Molten Salt System

作　　者：罗万 刘雅兰[2] 杨大伟 姜仕林 赵修良[1] LUO Wan;LIU Ya-lan;YANG Da-wei;JIANG Shi-lin;ZHAO Xiu-liang(School of Nuclear Science and Technology,University of South China,Hengyang 421000,China;Laboratory of Nuclear Energy Chemistry,Institute of High Energy Physics,Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]南华大学核科学技术学院,湖南衡阳421000 [2]中国科学院高能物理研究所核能与放射化学实验室,北京100049

出　　处：《核化学与放射化学》2022年第2期192-199,共8页Journal of Nuclear and Radiochemistry

基　　金：国家自然科学基金资助项目(No.21790373);国家杰出青年科学基金资助项目(No.21925603)。

摘　　要：在LiCl-KCl共晶盐中,研究了在不同温度下La^(3+)的反应动力学机理。首先,在723~873 K范围内,利用循环伏安法(CV)测得La^(3+)的扩散系数D为3.06×10^(-5)~6.08×10^(-5)cm^(2)/s,并根据Arrhenius方程计算了La^(3+)在电解质中的扩散活化能E_(D)=34.51 kJ/mol。随后,利用电化学阻抗谱技术(EIS)研究了La^(3+)在电极上的动力学参数并测得交换电流密度i_(0)为0.48~1.39 A/cm^(2)、反应速率常数k_(0)=2.04×10^(-4)~5.90×10^(-4)cm/s及反应活化能E_(a)=35.04 kJ/mol。通过Nyquist图和拟合的等效电路图研究La^(3+)在W电极上的反应动力学机理,发现在LiCl-KCl共晶盐中La^(3+)的电化学反应速率不仅受扩散控制还受电荷转移控制,且与温度成正相关。In this paper,the reaction kinetic mechanism of La^(3+) was studied in the LiCl-KCl eutectic salt at various temperatures.First,the diffusion coefficient of La^(3+)(D)measured by cyclic voltammetry(CV)increases from 3.06×10^(-5) cm^(2)/s to 6.08×10^(-5) cm^(2)/s with the temperature ranging from 723 K to 873 K,and the activation energy of La^(3+) diffusion(E_(D))in the molten salts is 34.51 kJ/mol calculated by the Arrhenius equation.Subsequently,the kinetic parameters of La^(3+) on the W electrode were studied by the electrochemical impedance spectroscopy(EIS).In the temperature range of 723-873 K,the exchange current density(i_(0))is measured to be 0.48-1.39 A/cm^(2),and the reaction rate constant(k_(0))is determined as 2.04×10^(-4)-5.90×10^(-4)cm/s.Moreover,the corresponding reaction activation energy(E_(a))is found to be 35.04 kJ/mol.The Nyquist plots and the fitted circuit diagrams explored the reaction kinetic mechanism of La^(3+) on a W electrode.It was illustrated that the electrochemical reduction rate of La^(3+) in the LiCl-KCl eutectic salt is controlled by diffusion and charge transfer,and it is positively correlated with temperature.

关 键 词：LiCl-KCl LaCl_(3) 扩散系数 电化学阻抗谱 动力学参数 

分 类 号：TL241.2[核科学技术—核燃料循环与材料] O615.1[理学—无机化学]