Nanocarbons development

Finally, the reproducibility of the nanocarbons and their hybrids is of paramount importance when implementing them into commercial devices. This will require the definition of key characteristics and the development of standard synthesis methodology that will also enable better comparison of results between research groups. 

Developing nanocarbons with high specific surface area (> 2000 m2/g) and with... 

The use of pyrolyzed polyacrylonitrile (PPAN) and polyaniline (PAni) (Fig. 15.8(d), (e)) as catalysts for the ODH of ethylbenzene should only be mentioned here for the sake of completeness. Although first results were quite promising [45], this concept has so far not been followed in terms of N-doped nanocarbon catalyst development. This is most likely due to the poor self-oxidation resistance as a result of polar C-N bonds. 

Scientific interest in nanocarbon hybrid materials to enhance the properties of photocatalysts and photoactive electrodes has been growing rapidly [1-8]. The worldwide effort to find new efficient and sustainable solutions to use renewable energy sources has pushed the need to develop new and/or improved materials able to capture and convert solar energy, for example in advanced dye-sensitized solar cells - DSSC (where the need to improve the photovoltaic performance has caused interest in using nanocarbons for a better cell design [9,10]) or in advanced cells for producing solar fuels [11-13]. 

The use of nanocarbon-semiconductor hybrid materials thus offers a great potential to the design and development of novel/improved photocatalysts and photoanodes, but it is necessary to have a detailed understanding of the many factors which determine the overall properties. This chapter will analyze these aspects presenting a concise analysis of the topic with selected relevant developments in the field, mainly in the last few years. 

Previous sections have demonstrated how nanocarbon-semiconductor hybrid materials provide a number of potential advantages for the development of advanced devices for a sustainable use of renewable energy. Two of the more relevant areas are (i) to improve the performances of DSSCs and (ii) to develop novel cells for producing solar fuels. 

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]. 

There is thus a great potential for using nanocarbon-semiconductor hybrids to develop improved devices, particularly for the more challenging area of using renewable energy, while most of the current studies are centered on environmental applications, for which there is limited need to develop advanced photocatalysts. 

Nanocarbon hybrids have recently been introduced as a new class of multifunctional composite materials [18]. In these hybrids, the nanocarbon is coated by a polymer or by the inorganic material in the form of a thin amorphous, polycrystalline or single-crystalline film. The close proximity and similar size domain/volume fraction of the two phases within a nanocarbon hybrid introduce the interface as a powerful new parameter. Interfacial processes such as charge and energy transfer create synergistic effects that improve the properties of the individual components and even create new properties [19]. We recently developed a simple dry wrapping method to fabricate a special class of nanocarbon hybrid, W03 /carbon nanotube (CNT) coaxial cable structure (Fig. 17.2), in which W03 layers act as an electrochromic component while aligned... 

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