Mo,W电极在MgCl_2-KCl-NaCl-CaCl_2熔盐中电解镁的钝化行为

Abstract

应用循环伏安法和计时电流法研究了Mg(Ⅱ)在MgCl2-KCl-NaCl-CaCl2四元熔盐体系中于(Mo、W)阴极上的放电过程及其钝化行为.结果表明,W电极放电反应的可逆性比Mo电极的好.后者的计时电流曲线偏离线性特征,且其阴极钝化比W严重.

The discharge process and passivation behaviors of Mg(Ⅱ) on cathode(Mo、W) in MgCl2-KCl-NaCl-CaCl2 molten salt system had been investigated by means of cyclic voltammetry and chronoamperometry.The composition of molten salt was MgCl(10%)+CaCl(20%)+NaCl(60%)+KCl(10%)(by mass) and the temperature of electrolysis was 725 ℃.The deposition potential of Mo was 37 mV more negative than that of W,while the peak current was sharper than Mo according to the voltammograms at 0.05 V/s,indicating that the passivation on Mo cathode is easier than W.The formation of MgO impurities during the electrolysis could cause the cathode passiration.However,the reversibility on the discharge reaction of W cathode was better than Mo electrode,and the reduction peak potential of W electrode almost unchanged with the scan rate.The I～t-1/2 curves demonstrated a positive linear relationship on W electrode,but deviated from the linear characteristics on Mo electrode due to the passivation.