Synthesis and structural characterization of carbon powder by electrolytic reduction of molten Li2CO3-Na2CO3-K2CO3
Synthesis and structural characterization of carbon powder by electrolytic reduction of molten Li2CO3-Na2CO3-K2CO3
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DOI：
10.1149/1.1464884
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发表时间：
2002-05
影响因子：
3.9
通讯作者：
B. Kaplan;H. Groult;A. Barhoun;F. Lantelme;T. Nakajima;V. Gupta;S. Komaba;N. Kumagai
中科院分区：
文献类型：
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作者：
B. Kaplan;H. Groult;A. Barhoun;F. Lantelme;T. Nakajima;V. Gupta;S. Komaba;N. Kumagai
提出了一种基于锂-钠-钾碳酸盐熔融低共熔混合物在450°C下电化学还原制备碳粉的新方法。透射电子显微镜观察揭示了三种形式的碳在粉末样品中的存在下，取决于沉积电位值：无定形碳，石墨，和纤维。通过X射线衍射测量证实石墨和无定形碳的存在。d 002值是相当恒定的，无论样品和接近0.34 nm。此外，通过X射线光电子能谱的表面分析揭示了属于锂氧化物的近金属锂和离子锂的存在。通过Brunaucr-Emmett-Teller（BET）方法测量比表面积。无论存款电位值，总的BET比表面积是远远高于相应的外部一个，因为孔壁的贡献。结果表明，在400°C真空干燥的碳粉，其比表面积随着沉积电位的增加而减小：从约850 m2 g-1（-2.4 V vs. CO2-O2）减小到约500 m2 g-1（-6.0 V vs. CO2-O2）。随着电势负值的增加，碳的成核和生长与近金属锂和/或锂氧化物的形成竞争。后者的存在诱导一些纳米孔的闭合。
A new method was proposed for the preparation of carbon powders based on the electrochemical reduction of a fused eutectic mixture of lithium-sodium-potassium carbonates at 450°C. Transmission electron microscopy observations have revealed the presence of three forms of carbon in the powder samples depending on the deposition potential values: amorphous carbon, graphite, and fibers. The presence of graphite and amorphous carbon was confirmed by X-ray diffraction measurements. The d 002 values were rather constant whatever the sample and close to 0.34 nm. Moreover, surface analyses by X-ray photoelectron spectroscopy revealed the presence of nearly metallic and ionic lithium belonging to lithium oxides. The specific areas were measured by the Brunaucr-Emmett-Teller (BET) method. Whatever the deposit potential values, the total BET specific surface area is much higher than that corresponding to external one because of the pore walls contribution. It has been shown that, for carbon powder dried at 400°C under vacuum, the specific surface area decreased as the deposition potential became more cathodic: from about 850 m 2 g -1 at -2.4 V vs. CO 2 -O 2 to about 500 m 2 g 1 at -6.0 V vs. CO 2 -O 2 . With increasing negative values of the potential, the nucleation and the growth of carbon competes with the formation of nearly metallic lithium and/or lithium oxides. The presence of the latter induces the closure of some nanopores.