La^(3+)在LiCl-KCl熔盐中E-pO^(2-)的稳定性相图

E-pO_(2)-Stability Phase Diagram of La^(3+)in LiCl-KCl Molten Salt

主要研究了723~813 K下LiCl-KCl-LaCl_(3)熔盐体系中La^(3+)在惰性W电极上的电化学行为。在惰性W电极上La^(3+)约在-2.04 V(vs.Ag/AgCl)被还原,该反应是一步三电子转移的过程。在LiCl-KCl-LaCl_(3)熔盐体系中利用开路计时电位计算La^(3+)/La在W电极上的氧化还原电位、形成LaCl_(3)吉布斯自由能以及La^(3+)活度系数。采用电位滴定法研究LaCl_(3)与氧化物离子的反应,滴定曲线表明氧化物的沉淀为LaOCl。根据实验得到的表观电极电位、活度系数和相关的热力学数据,绘制了La-O稳定性相图。E-pO^(2-)稳定相图显示La^(3+)在723 K和较高O^(2-)的浓度范围内稳定存在的化合物为LaOCl。

This work concerns the electrochemical behaviors of La^(3+)on W electrodes in the LiCl-KCl-LaCl_(3)molten salt at 723-813 K.The results show that La^(3+)is reduced at about-2.04 V(vs.Ag/AgCl)on inert W electrode,which is a one-step three-electron transfer process.The redox potential,Gibbs free energy and activity coefficient of La^(3+)/La are calculated by open circuit chronopotentiometry on W electrode in LiCl-KCl-LaCl_(3)molten salt.Potentiometric titration was used to study the reaction of lanthanum chloride with oxide ions.The titration curve shows that the precipitate of oxide is LaOCl.According to the experimental apparent electrode potential,activity coefficient and relevant thermodynamic data,the phase diagram of La-O stability was drawn.The stable phase diagram of E-pO^(2-)shows that LaOCl is the most stable compound in the range of higher O^(2-)concentration at 723 K.