Nanocarbon Anode Materials

Hitherto, graphitic carbons are still the dominant anode materials for LIBs. This indicates the importance of carbonaceous anode materials in LIBs. Here, we mainly introduce CNTs and carbon nanofibers as anode candidates for LIBs. 

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One synthesis approach that does not rely on CNT formation from the gas phase is molten salt synthesis. The reactor consists of a vertically oriented quartz tube that contains two graphite electrodes (i.e. anode is also the crucible) and is filled with ionic salts (e.g. LiCl or LiBr). An external furnace keeps the temperature at around 600 °C, which leads to the melting of the salt. Upon applying an electric field the ions penetrate and exfoliate the graphite cathode, producing graphene-type sheets that wrap up into CNTs on the cathode surface. Subsequently, the reactor is allowed to cool down, washed with water, and nanocarbon materials are extracted with toluene [83]. This process typically yields 20-30 % MWCNTs of low purity. 

The protons/electrons produced in water oxidation at a photoanode side of a PEC device could be used (on the cathode side) to reduce C02 to alcohols/hydrocarbons (CH4, CH30H, HC00H, etc.). In this way, an artificial leaf (photosynthesis) device could be developed [11]. While nanocarbon materials containing iron or other metal particles show interesting properties in this C02 reduction [106], it is beyond the scope of this chapter to discuss this reaction here. It is worthwhile, however, to mention how nanocarbon materials can be critical elements to design both anode and cathode in advanced PEC solar cells. Nanocarbons have also been successfully used for developing photocatalysts active in the reduction of C02 with water [107]. 

Over the last decade, novel carbonaceous and graphitic support materials for low-temperature fuel cell catalysts have been extensively explored. Recently, fibrous nanocarbon materials such as carbon nanotubes (CNTs) and CNFs have been examined as support materials for anodes and cathodes of fuel cells [18-31], Mesoporous carbons have also attracted considerable attention for enhancing the activity of metal catalysts in low-temperature DMFC and PEMFC anodes [32-44], Notwithstanding the many studies, carbon blacks are still the most common supports in industrial practice. 

To overcome the stability problem, it is obvious that an alternative approach to material synthesis would be needed. In this respect a recent report suggested that iron oxide encapsulated in meso- and macroporous carbon can be used as anode in Li batteries and reaches a greatly improved reversibility and rate performance. At the same time, a similar structure for a cathode material based on iron and lithium fluoride was synthesized and investigated. It was demonstrated that encapsulation of transition metal-metal fluoride in nanocarbon might be an effective strategy to improve the cycling performance of such a cathode material. ... 

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