Synchronized High-Speed Microscopy and Thermoanalytical Measurement for Sub-mm/sub-ms-scale Cathodic Behavior in Molten Salt Electrolysis

The electrochemically deposited liquid metal (Me = Ca, Li, or their alloys) in the molten chloride works as powerful reductant for TiO₂ or other metal oxides; however, the electrolysis efficiency should be enough high if much lower oxygen level in metal phase was required. A detailed understanding of the cathodic behavior is necessary to control and optimize the electrolysis. In this study, to clarify the morphological and thermal characteristics of a cathodic electrode in a molten MeCl melt, we simultaneously performed electrochemical measurements and thermal measurements using an ultrafine thermocouple inserted inside a Mo electrode. Changes in the electrode interface were recorded at 500-μs intervals using a synchronized high-speed digital camera. It was possible to trace the change in the electrodeposition pattern in each potential quickly and sensitively, which was difficult to determine in only the electrochemical potential-current response.