Abstract: The electrochemical behavior of cathodic process was investigated by means of cyclic voltammetry, electrochemical impedance spectroscopy and square wave voltammetry in both Na₃AlF₆-Al₂O₃ and Na₃AlF₆-Al₂O₃-KF systems. The results showed that the reduction peaks shifted negatively and oxidation peak shifted positively with the increase of scan rate from the measurement of cyclic voltammetry. The reaction process was irreversible under the condition of lower scan rate, and the reaction was relatively flat and stable, but the reduction process became reversible gradually with the increase of scan rate. Because of polymerization phenomenon at the electrode-site, inductance phenomenon appeared in the high frequency area when KF was absent in the molten salt. Under the condition of containing KF, the reaction was predominantly controlled by charge transfer and diffusion. The growth of the concentration of KF could decrease diffusion impedance coefficient and increase reaction current. The charge transfer process gradually replaced the diffusion process and accelerated oxidation rate. Meanwhile the reduction and oxidation process became reversible. Adding KF also suppressed the deposition of aluminum and alloying effect was obvious. Through Gaussian fitting for the cathodic prewave, electron transfer numbers of Al ion were 1.19, 1.02 and 0.75 in different systems of KF concentration（0，3%，5%）respectively.

Key words: KF, cathodic electrochemistry, aluminium electrolysis, process control, electrolytes

摘要： 采用循环伏安法、交流阻抗法和方波伏安法等电化学测量技术，考察了KF对Na₃AlF₆-Al₂O₃熔盐电解体系的阴极过程的影响。研究结果表明：在Na₃AlF₆-Al₂O₃和Na₃AlF₆-Al₂O₃-KF电解质体系的循环伏安曲线中，还原峰随着扫描速率的增大而负移，氧化峰随着扫描速率的增大而正移，在扫描速率较低（25～100 mV·s^-1）的情况下，反应过程不可逆，反应过程相对平缓稳定；随着扫描速率的提高，电极可逆性相对提高。由于电极附近铝离子的聚合现象，使得在无KF的熔盐体系下，交流阻抗的高频区出现了感抗现象；在含KF的体系下，反应是由电化学反应过程和扩散过程共同控制的，且随着KF含量的增加，Warburg阻抗系数减小，电化学反应过程控制逐步取代扩散过程控制；反应电流也随之增大，氧化速率加快，还原和氧化过程可逆性降低。同时KF的加入抑制了铝的沉积，合金化作用比较明显，通过对阴极前波进行高斯拟合，得到不同KF含量（0、3%、5%）体系下的铝离子的电子转移数分别为1.19、1.02、0.75。

关键词: KF, 阴极电化学, 铝电解, 过程控制, 电解质