在CaCl2熔盐中, 利用固体透氧膜(SOM)法直接电解混合氧化物NiO-CeO2制备CeNi5合金, 并与熔盐电解法(FFC)进行了对比. 阴极的制作方法与FFC法相同, 阳极为碳饱和Cu(或Sn) 液, 采用只允许氧离子通过的透氧膜隔开阴极和阳极, 这样可以采用较高的电解电压 (3.5 V)以获取更高的电解速率. 研究了SOM法制备CeNi5合金的可行性和影响因素, 如电解温度、电解时间, 以及产物的相组成和形 貌等. 结果表明: 通过SOM法, NiO-CeO2可完全还原为CeNi5. 电解中间产物的相组成分析表明, CeNi5的形成过程为: NiO首先还原为 Ni, 与随后生成的CeOCl反应生成CeNi5. SOM法与FFC法对比表明, 2.5 g的烧结试样采用SOM法电解3 h可电解完全, 电流效率为75.5%, 能耗为4.03 kW•h/kg; 采用FFC法需12 h才能电解出纯的CeNi5合金, 其电流效率为26.1%, 能耗为10.27 kW•h/kg. 相比于FFC法, SOM法具有更好的工业化应用前景.
Ce–Ni base alloy CeNi5 is often used as the hydrogen storage alloy in Ni–H batteries. Its application is more or less limited by the high cost in the traditional preparing process. Therefore, lots of researchers have paid more attention to develop a novel process with high production efficiency and low cost. The goal of the present research was to demonstrate the technical viability of a new process (solid–oxygen–ion conducting membrane process, i.e., SOM process) for the production of CeNi5 alloy directly from its oxide precursors. This process was improved on the basis of FFC process (Fray–Farthing–Chen Cambridge process): (1) the preparation of cathode was he same as that in FFC process, (2) Cu (oSn) liquid saturated with carbon was used as anode separated from the melt ba yttria–stabilized zirconia tube in which only oxygen–ion was permeated to prevent the side reactions and decomposition of molten salts taking place until a voltage as high as 3.5 V. This paper was focused on the preparation of hydrogen storage alloy CeNi5 by SOM process, some parameters such as molten salt temperature, electrolytic time, configurations and phase compositions of products were investigated. The results show that NiO–CeO2 pellets can be completely reduced to CeNi5 alloy by SOM process. The analysis of phase compositions of intermediate products indicates that the reduction of NiO–CeO2 starts from NiO, it reduces firstly into Ni, then reacts with newly–formed CeOCl and finally forms CeNi5. The comparison of FFC and SOM processes shows that for SOM, NiO–CeO2 pellet (2.5 g) can be completely reuced to CeNi5 after electrolyzed for 3 h, and the current efficiency is 75.5%, the electrolysis energy consumption is only as low as 4.03 kW·h/kg; while for FFC, it takes 12 h for the same pellet to be reduced to pure CeNi5, and the current efficiency is 26.1% but the electrolysis energy consumption is 10.27 kW·h/kg. It could be concluded that SOM process has a bight future for industrial application.
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