Electrochemical Reduction Behavior of Pure Metal Oxides Without Supporting Electrolytes at Ultrahigh Temperatures

Molten oxide electrolysis is an emerging method that uses electrons as reducing agents to produce metals in extreme applications, such as in lunar metallurgy. However, the electrolyte composition complexity of molten oxides limits the further understand of their electrochemical reduction behavior. Herein, a laser-thermal ultrahigh-temperature molten oxide electrolytic device was autonomously designed, and we first investigated the electrochemical reduction behavior of pure metal oxides, specifically Ta₂O₅, in the absence of supporting electrolytes at ultrahigh temperatures exceeding 2000 °C. The redox reactions within the molten Ta₂O₅ pool were verified through staircase cyclic voltammetry. The results demonstrated that the reduction of Ta⁵⁺ occurred as a one-step process at the cathode, accompanied by the generation of oxygen gas at the anode. Furthermore, the influence of electrolytic parameters, including different constant voltages and constant currents, on the electrolytic behavior of Ta₂O₅ was examined, and a mid-scale model was proposed to explain the morphological evolution of electrolytic product under different conditions. Overall, a laser-thermal electrochemical extraction strategy is proposed for directly extracting metal and oxygen from pure metal oxides, eliminating the need for auxiliary electrolytes. This approach is anticipated to provide valuable guidance for the design and development of electrochemical metallurgy in extreme environments.