Abstract

The cathode reduction of Ce(III) ions to form a metal at an inert Mo electrode in the molten 3LiCl–2KCl eutectic is studied in a temperature range of 723–823 K by stationary and nonstationary electrochemical methods. In voltammograms, a single cathodic current peak is recorded at a potential of –3.19 ± 0.10 V, and an anodic current peak associated with the cathodic current peak is recorded at a potential of ‒3.10 ± 0.08 V vs. the chlorine reference electrode. Therefore, the reduction process occurs by the reaction Ce³⁺ + 3\({\bar {e}}\) → Ce. An analysis of cyclic voltammograms showed that the current peak potential of the Ce(III) ion reduction shifts to a negative range as the scan rate increases. At the same time, the current corresponding to the cathodic peak is directly proportional to the square root of the polarization rate in the entire potential range under study. An increase of the scan rate is shown to decrease the transfer coefficient (α), i.e., to increase in the irreversibility of the cathodic process. According to the theory of cyclic voltammetry, the cathode reduction of cerium ions is an irreversible process, which is single-stage and is controlled by the charge transfer rate. The temperature dependence of the apparent standard potential of the pair Ce(III)/Ce is measured by zero-current chronopotentiometry. The experimental values are described by linear equation \(E_{{{{{\text{Ce}}\left( {{\text{III}}} \right)} \mathord{\left/ {\vphantom {{{\text{Ce}}\left( {{\text{III}}} \right)} {{\text{Ce}}}}} \right. \kern-0em} {{\text{Ce}}}}}}^{{\text{*}}} = - \left( {{\text{3}}{\text{.455}} \pm {\text{0}}{\text{.010}}} \right)\) + (6.1 ± 0.1) × 10^–4T ± 0.009 V. The changes in the apparent standard Gibbs energy, the enthalpy, and the entropy of the reaction of formation of cerium thrichloride from the elements in the molten 3LiCl–KCl eutectic and the activity coefficient of CeCl₃ are calculated.

中文翻译：

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熔融3LiCl-2KCl共晶中Ce（III）离子的阴极还原

摘要

通过固定和非固定电化学方法研究了在723-823 K温度范围内，熔融3LiCl-2KCl共晶中惰性Mo电极上的Ce（III）离子在金属上的阴极还原作用，从而形成金属。在伏安图中，单个阴极电流峰的电位为–3.19±0.10 V，与阴极电流峰相关的阳极电流峰的电位为reference3.10±0.08 V（相对于氯参比电极）。因此，还原过程通过Ce ³⁺ + 3 \（{\ bar {e}} \）的反应而发生→Ce。对循环伏安图的分析表明，随着扫描速率的增加，Ce（III）离子还原的当前峰值电势移至负范围。同时，在研究的整个电位范围内，对应于阴极峰的电流与极化率的平方根成正比。扫描速率的增加显示出降低了传输系数（α），即增加了阴极过程的不可逆性。根据循环伏安法的理论，铈离子的阴极还原是不可逆的过程，它是单阶段的，并且受电荷转移速率的控制。Ce（III）/ Ce对的表观标准电位的温度依赖性通过零电流计时电位法测量。\（E _ {{{{{\ text {Ce}} \ left（{{\ text {III}}} \ right）} \ mathord {\ left / {\ vphantom {{{\ text {Ce}} \\ left （{{\ text {III}}} \ right）} {{\ text {Ce}}}}} \ right。\ kern-0em} {{\ text {Ce}}}}}} ^ {{\ text {*}}} =-\ left（{{\ text {3}} {\ text {.455}} \ pm {\ text {0}} {\ text {.010}}} \ right）\） + （6.1±0.1）×10 ^–4 T ±0.009V。表观标准Gibbs能量，焓和由熔融3LiCl-KCl共晶元素中的三氯化铈形成反应的熵和活度的变化计算CeCl _3的系数。