Cathode Electrochemical Behavior of Aluminum Electrolysis in NaF-NaCl Based Molten Salt

Selective and efficient electrochemical analytical methods for the depositing process of metal aluminum are significant and necessary. The electrochemical measurement methods are based on the means of cyclic voltammetry, square wave voltammetry and constant potential electrolysis. The above methods are even never used to analyze the depositing process of metal aluminum in NaF-NaCl-Al2O3 and NaF-NaCl-NaAlO2 molten salt. Cyclic voltammetry analysis showed that Al3+ ions were reduced to metal aluminum through two consecutive steps. From the analysis of square wave voltammetry curve, the main reaction on the electrode was the reduction of metal sodium in the NaF-NaCl system, and the electron transfer number of the reaction was 0.80. With the addition of NaAlO2 and Al2O3 in the electrolyte, the electron transfer numbers of the two reduction steps were about 3.0. The process of reduction of Al3+ ions to aluminum was further proved by the analysis of the electrolysis curve at constant potential. The diffusion rate of Al3+ions and the rate of Al3+ reduction reaction increased with the addition of NaAlO2 and Al2O3 and the change of the potential.