Selective formation of Ce-Ni hydrogen storage alloys by electro-deposition in LiCl-KCl-CeCl3 melts using Ni as cathode

Abstract

The electrochemical formation of Ce-Ni alloy and its nucleation mechanism were researched in LiCl-KCl melts using different electrochemical methods. Cyclic voltammetric and square wave voltammetric results indicated that the electrochemical reduction of Ce (III) appeared at a less negative value on Ni electrode than that recorded on W electrode because of the formation of Ce-Ni alloy compounds. The nucleation mechanism of Ce was found to be the progressive nucleation on Ni electrode based on Scharifker-Hill model. The change of electrode surface morphology with deposited time was observed by SEM, which indicated that the morphology of Ce deposited on Ni electrode was dendritic. Ce-Ni alloys were prepared using potentiostatic electrolysis, and checked by XRD and SEM-EDS. The results showed that hydrogen storage alloys of CeNi2, CeNi3 and CeNi5 were gained by controlling applied potential. Furthermore, the thermodynamic properties of Ce-Ni compounds were estimated in the temperature range of 823–898 K by open circuit chronopotentiometry.