Since the early 2000s, when the Fray-Farthing-Chen (FFC, direct mechanism) and the Ono-Suzuki (OS, indirect mechanism) processes for the reduction of titanium oxide were elucidated, several additional metal oxides (ZrO₂, Ta₂O₅, Cr₂O₃, and Nb₂O₅) have been reported to electrolytically reduce to their metallic state in molten CaCl₂-CaO.^1-3 In our hands, the electrolytic reduction of cerium oxide has resulted in mixed degrees of success due to side reactions within the molten salt. Cyclic voltammetry (CV) was performed in order to identify the products of these side reactions, and resulted in greater understanding of the system; based on CV results, parameters were refined, resulting in an improved production of Ce⁰. When Ce⁰ was successfully produced by electrolytic oxide reduction, a large amount of passed charge was required due to various inefficiencies of the process, requiring further optimization. Anode material has been identified as a possible source of inefficiency, as it degrades throughout an experiment. Currently, pyrolytic graphite is used as the anode, which leads to carbon dissolution and contamination of the salt bath. As such, the goal of this study is to identify an inert anode material and operational parameters to ensure greater yields of metallic product.

References

• Chen, G. Z., Fray, D. J. & Farthing, T. W. Direct electrochemical reduction of titanium dioxide to titanium in molten calcium chloride. Nature 407, 361-364 (2000).
• Claux, B., Serp, J. & Fouletier, J. Electrochemical reduction of cerium oxide into metal. Electrochimica Acta 56, 2771-2780, (2011).
• Suzuki, R. O., Ono, K. & Teranuma, K. Calciothermic reduction of titanium oxide and insitu electrolysis in molten CaCl₂. Metallurgical and Materials Transactions B 34, 287-295, (2003).

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