Effect of Ni2+ and Cr3+ on electrodeposition of uranium dioxide in LiCl–KCl molten salt

To electrodeposit uranium dioxide from LiCl–KCl molten salt containing Cr 3+ and Ni 2+ , a series of electrochemical techniques were employed to investigate the electrochemical behavior of UO 2 2+ , Cr 3+ , and Ni 2+ . CV and SWV measurements revealed that Cr 3+ is reduced to metallic Cr through a two-step process, while Ni 2+ undergoes a one-step, two-electron process to form metallic Ni. UO 2 2+ is reduced to uranium dioxide via two successive one-electron transfer steps, and its reduction mechanism remains unaffected by the presence of Cr 3+ and Ni 2+ . Chronoamperometry was employed to study the influence of Cr 3+ on the nucleation mechanism of UO 2 2+ , which indicated that the addition of Cr 3+ could decrease the nucleation density of uranium dioxide. In addition, the effects of Cr 3+ and Ni 2+ on the electrodeposition of uranium dioxide were separately explored. In the presence of Cr 3+ , the deposited product contained only uranium dioxide and no Cr was deposited, but the current efficiency was reduced. Pulse electrolysis was carried out and found that current efficiency could be improved by pulse electrolysis in the presence of Cr 3+ . The introduction of Ni 2+ led to the co-deposition of uranium dioxide and Ni, while significantly accelerating the extraction rate of uranium dioxide. Thermodynamic analysis and experimental results indicate that this enhancement arises from the in situ reduction of UO 2 2+ by the deposited Ni, a process that proceeds much faster than the direct electrochemical reduction of UO 2 2+ .