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Study on the mechanism of ionic mobility in molten carbonate mixtures.

熔融碳酸盐混合物中离子迁移机制的研究。

基本信息

批准号：
07454183
负责人：
OKADA Isao
金额：
$ 4.54万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1997
项目状态：
已结题

项目摘要

The molten binary systems (Li, K)_2CO_3 and (Li, Na)_2CO_3 at their eutectic compositions are the candidates for the electrolytes for the molten carbonate fuel cells (MCFC). The internal mobilities in the system (Li, Na)_2CO_3 have been measured by countercurrent electromigration ; those in the system (Li, Na)_2CO_3 at were previously measured In the former system the mobility of Na^+ is somewhat greater than that of Li^+ at all the investigated range of composition and temperature. The internal mobilities of Li^+, u_<Li>, in these two systems are well expressed by the empirical equation : u_<Li>=[A/ (V_m-V_0)] exp (-E/RT), where V_m is the molar volume of the mixture ; V_0, A and E are constants nearly independent of the second cation. The mobilities in the ternary system (Li, Na, K)_2CO_3 at the eutectic composition (43.5-21.5-25.0 mol%) have also been measured. The order of the mobilities of these cations is as follows : u_<Li>-u_K<u_<Na> (at 500ﾟC), u_<Li><u_<Na>-u_K (at 600ﾟC) and u_<Li><u_<Na>-u_K (at 750ﾟC). These results can be interpreted in terms of the dynamic dissociation model previously presented by us. This suggests that the internal mobilities of other cations could be semi-quantitatively predicted by this model. Polarized Raman spectroscopy has been applied for systems (Li, Na)_2CO_3 to investigate the rotational relaxation of the C_<3V> axis of the CO_3^<2-> ion. No appreciable relation has been found between the mobility and the rotationa motion.

熔融二元系(Li，K)_2CO_3和(Li，Na)_2CO_3的共晶组成是熔融碳酸盐燃料电池(MCFC)的候选电解液。用逆流电迁移法测量了(Li，Na)_2CO_3体系的内迁移率，用前一种方法测量了(Li，Na)_2CO_3体系的内迁移率。在所研究的组成和温度范围内，Na~+的迁移率略大于Li~(2+)的迁移率。Li~+，u_<Li>在这两个体系中的内迁移率可用经验方程U_<Li>=[A/(V_m-V_0)]exp(-E/RT)很好地表示，其中V_m是混合物的摩尔体积，V_0、A和E是几乎与第二阳离子无关的常数。本文还测定了(Li，Na，K)_2CO_3三元体系在共晶组成(43.5-21.5-25.0摩尔%)时的迁移率。这些阳离子的迁移率顺序如下：U_<Li>-u_K&lt；u_&lt；Na&gt；(在500ﾟC时)，u_<Li>&lt；u_&&lt；-u_K(在600ﾟC时)和u_<Li>&lt；u_&lt；Na&gt；-u_K(在750ﾟC时)。这些结果可以用我们以前提出的动态离解模型来解释。这表明该模型可以半定量地预测其他阳离子的内部迁移率。本文用偏振拉曼光谱研究了(Li，Na)_2CO_3体系中CO_3~(2-)~(2-)~(2-)~(2-)的C_&lt；3V&gt；轴的转动弛豫。还没有发现机动性和旋转运动之间有明显的关系。