Study The Reduction Mechanism Of Zr(?) On Tungsten And Nickel Electrodes In LiCl-KCl Molten Salt

Zirconium and nickel have higher melting points.The preparation of nickel-zirconium alloys by the smelting method and the metal-to-doping method of the traditional alloy preparation method requires a higher experimental temperature,a higher purity of the raw materials,there are problems such as complicated processes and high energy consumption.The mechanical alloying method has strict restrictions on the purity of the raw material and the size of the raw material particle size,and the cost is also huge.The use of molten salt electrolysis to prepare nickel-zirconium alloy will solves many inconveniences.The molten salt electrolysis method does not require high purity of the raw materials,the experimental temperature is relatively low,the equipment is simple and the process is short,and the main thing is that the alloy prepared by the molten salt electrolysis method has a high purity,which can meet the actual production needs.The electrochemical reduction mechanism of Zr???on tungsten electrode in LiCl-KCl molten salt at 873 K was studied in this paper by cyclic voltammetry,linear scanning voltammetry,square wave voltammetry,chronoamperometry and chronopotentiometry.At the same time,the cyclic voltammetry and square wave voltammetry were used to study the electrochemical process of Zr???on the nickel electrode,which provided a theoretical basis for the preparation of nickel-zirconium master alloy by molten salt electrolysis.Cyclic voltammetry test results displayed that the electrochemical reduction of Zr???on the tungsten electrode in 49.5%LiCl-49.5%KCl-1wt%ZrCl₄ molten salt at873 K was a quasi-reversible reaction process of 2-step electrochemical reduction.The linear scanning voltammetry test results further indicated that the potential of electrochemical reduction of Zr???on the tungsten electrode in molten salt was about-0.9 V?vs Ag/AgCl?and about-1.18 V?vs Ag/AgCl?,the electrochemical reduction process was controlled by diffusion.According to the linear scanning voltammetry test results and square wave voltammetry test results,the number of electrons transferred during the electrode reaction was determined that the reduction peak appearing near-0.9 V?vs Ag/AgCl?was an electrochemical process for transferring 2electrons,the electrode reaction equation occurring near-0.9 V?vs Ag/AgCl?was Zr???+2e^-?Zr???,the electrode reaction corresponding to the reduction peak appearing near-1.18 V?vs Ag/AgCl?was also an electrochemical process to transfer2 electrons,the electrode reaction equation occurring near-1.18 V?vs Ag/AgCl?was Zr???+2e^-?Zr?0?.According to the Cottroll equation,the diffusion coefficient was5.898×10^-5 cm²·s^-1 by fitting the chronoamperometric test data.The chronopotential test results verified the correctness of the cyclic voltammetry test,the linear scanning voltammetry test and square wave voltammetry test results.The electrochemical reduction of Zr???on nickel electrode in molten salt was studied at 873 K by cyclic voltammetry and square wave voltammetry.The results of cyclic voltammetry and square wave voltammetry found that a reduction peak appeared near-0.5 V,-0.9 V and-1.8 V?vs Ag/AgCl?.The reduction peaks at-0.5 V?vs Ag/AgCl?and-0.9 V?vs Ag/AgCl?were analyzed that corresponding to the two-step reduction process of Zr???on the nickel electrode in the molten salt,the reduction peak appearing near-1.8 V?vs Ag/AgCl?corresponds to the formation of the nickel-zirconium intermediate alloy.The product obtained by constant potential electrolysis at-1.8 V?vs Ag/AgCl?was found by XRD test.The reduction peak which was about-1.8 V?vs Ag/AgCl?corresponds to the formation NiZr alloy.