Direct electrochemical preparation of CeNi5 and LaxCe1−xNi5 alloys from mixed oxides by SOM process

A novel SOM process was used to prepare CeNi₅ and La_xCe_1−xNi₅ hydrogen storage alloys directly from their mixed oxides. The electrolytic reduction was carried out in molten CaCl₂ system at 1000 °C. The reduction mechanism was investigated by analyzing the chemical compositions and the phase constitutions of the intermediate products of electrolysis. The results suggested that the reduction of NiO-CeO₂ may take place in two steps: first, NiO was reduced into Ni and CeO₂ reacted with CaCl₂ to form CeOCl, then Ni reacted with CeOCl leading to the formation of CeNi₅. It was found that the reduction rate increased while decreasing the pressure load of the mixed oxide pellets. Furthermore, CeNi₅ could not be produced if the pressure load was lower than 10 MPa. It was also found that the pellets of NiO-CeO₂ could be completely reduced to CeNi₅ alloy by the SOM process, which was greatly excelled than FFC process. The successful preparation of La_xCe_1−xNi₅ (x = 0-1) alloy reported here suggests that the SOM process may be promising for the industrial application of producing such alloys.