Electrochemical Behavior Study Of Ce On Zn,Al And Al-Zn Alloy Electrodes With Different States

Nuclear energy is widely used as a clean,stable and efficient energy source with no carbon emissions and high energy density.However,the spent fuel generated in the process of nuclear energy application contains a large number of radioactive elements.Therefore,it is especially important to dispose of the spent fuel safely and efficiently.Among the spent fuel reprocessing technologies,dry reprocessing based on molten salt electrolysis is considered the most promising dry reprocessing technology because it is economical,environmentally friendly,and can withstand high radiation doses and effectively reduce critical safety risks.The spent fuel contains plenty of actinides（Ans）that can be recovered and recycled,and electrochemical studies of Ans are important to separate Ans from the spent fuel.Since Ans is radioactive,lanthanide（Lns）,which has similar chemical properties to Ans,is used instead of Ans in electrochemical studies.The choice of electrode in molten salt electrolysis has a certain influence on the study of electrochemical properties of Lns.Thus,it is important to choose a suitable electrode for the study of electrochemical mechanism of Lns.Cerium（Ce）has the same electronic configuration as U and is chemically close to U and Pu,The electrochemical behavior of Ce on different electrodes in the molten salt system and the related kinetic thermodynamic parameters are studied in this paper,the details of the study are as follows:（1）The electrochemical reduction mechanism of Ce（Ⅲ）on inert W electrode was investigated by various electrochemical methods.The one-step three-electron generation of Ce metal from Ce（Ⅲ）on inert W electrode was revealed.The diffusion coefficient of Ce（III）on the inert W electrode is 9.050×10^-5 measured by chronopotentiometry at 773 K The exchange current density of Ce（III）on inert W electrode was calculated by linear polarization method in the range of 0.03584-0.12873 A cm^-2,and the reaction activation energy is 35.306 k J mol^-1 The relationship between apparent electrode potential and temperature was obtained by open-circuit chronopotentiometry and dynamic current methods.（2）The electrodeposition process of Ce（Ⅲ）on Zn film,Al film,and Al-Zn film was investigated by various electrochemical methods.The co-deposition processes of Ce（Ⅲ）with Zn（Ⅱ）,Al（Ⅲ）,Zn（Ⅱ）-Al（Ⅲ）ions were studied by cyclic voltammetry,square wave voltammetry,and open-circuit chronopotentiometry,respectively,and the electrode potentials of the intermetallic compounds formed in each system were measured.（3）The electrodeposition mechanism,electrode process kinetics and thermodynamics of Ce（III）on solid Al,liquid（Zn,Al,Al-Zn）electrodes were studied by various electrochemical methods.It is a fast transfer three-electron process on all three liquid electrodes.By linear polarization method in obtaining Ce（III）exchange current density versus temperature on solid Al,liquid（Zn,Al,Al-Zn）electrodes.Ce（III）precipitates a positive shift in potential on liquid（Zn,Al,Al-Zn）electrodes with an obvious depolarizing effect,with a maximum polarization value of 0.71 V on high melting point Al electrode.The activity coefficients of Ce on different liquid electrodes（Zn,Al,Al-Zn）electrodes were obtained by coulometric titration and electromotive force method as a function of temperature.