Carbon support materials mesoporous

The sitosterol hydrogenation and deactivation kinetics was determined in a shaking constant-pressure batch reactor by using the new type of synthetic support material (mesoporous carbon Sibunit) for palladium (4wt% Pd) [55]. 

Garcia G, Florez-Montano J, Hemandez-Creus A, Pastor E, Planes GA (2011) Methanol electrooxidation at mesoporous Pt and Pt-Ru electrodes a comparative study with carbon supported materials. J Power Sources 196 2979-2986... 

Since the discovery of carbon nanotubes in the early 1990s [273] there has been emerging interest in their applicability as catalyst supports for low-temperature PEMFCs. Recently, Lee et al. reviewed the area of Pt electrocatalyst preparation techniques using carbon nanotubes and nanofibers as supports [274]. Here, the emphasis will be on the impact of novel nanostructured carbon supports (ordered mesoporous materials, nanotubes, and nanofibers) on the electrocatalytic activity with respect to direct fuel cell anodes. 

Mesoporous carbon materials were prepared using ordered silica templates. The Pt catalysts supported on mesoporous carbons were prepared by an impregnation method for use in the methanol electro-oxidation. The Pt/MC catalysts retained highly dispersed Pt particles on the supports. In the methanol electro-oxidation, the Pt/MC catalysts exhibited better catalytic performance than the Pt/Vulcan catalyst. The enhanced catalytic performance of Pt/MC catalysts resulted from large active metal surface areas. The catalytic performance was in the following order Pt/CMK-1 > Pt/CMK-3 > Pt/Vulcan. It was also revealed that CMK-1 with 3-dimensional pore structure was more favorable for metal dispersion than CMK-3 with 2-dimensional pore arrangement. It is eoncluded that the metal dispersion was a critical factor determining the catalytic performance in the methanol electro-oxidation. 

It should be mentioned that the structure of carbon supports could have significant influence on the electro-catalytic properties of the nanocomposite catalysts. Recently, Pt/Ru nanoclusters prepared by the alkaline EG method were impregnated into a synthesized carbon support with highly ordered mesoporous. Although the Pt/ Ru nanoclusters can be well dispersed in the pores of this carbon substrate, the long and narrow channels in this material seem not suitable for the application in... 

The object of the present study was to use in the above mentioned hydrogenations improved carbon supported catalysts, which could compete with the Pd black catalyst. Carbon materials are common supports, their surface properties can be modified easily and it is possible to prepare carbons with different proportion of micro-, meso- and macropores, which can be key factors influencing their performances. A highly mesoporous carbon was synthesised and used as support of Pd catalysts in the enantioselective hydrogenations. To our knowledge this is the first report on the use of highly mesoporous carbon for the preparation of Pd catalysts for liquid-phase hydrogenation. 

Alternative support materials are being investigated to replace carbon black as support in order to provide higher corrosion resistance and surface area. These supports can be classified into (i) carbon nanotubes and fibers (ii) mesoporous carbon and (iii) multi-layer graphene and they are presented in detail in the following section. 

Despite the advantages offered by CNTs and CNFs, there are still many obstacles (cost, synthesis methods) to overcome to allow large-scale production. Another type of catalyst support material is mesoporous carbon that provides high surface area and conductivity [100, 141]. It can be classified into ordered (OMC) and disordered (DOMC) mesoporous carbon [100], OMCs have been extensively used as catalyst support materials for fuel cells [140,142-146], The large surface area and 3D connected monodis-persed mesospheres facilitate diffusion of the reactants, making them very attractive materials as catalyst supports [100]. 

With rapid development of zeotypic materials and mesoporous solids and their application in heterogeneous catalysis, HRTEM shows its advantages in distinguishing the ultrastructural features [40, 41], Carbon materials are used as support in catalytic reactions due to some of their specific characteristics and many publications report the TEM investigations on various forms of carbon related materials [42-48],... 

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. 

Catalysts usually consist of two or more components in which the various constituents are assembled in the desired structure and shape. In this chapter we will consider the synthesis of a set of building blocks for the catalyst. The building blocks coiasidered are support materials (silica, alumina and carbon), zeolites and mesoporous materials. Often the catalyst assembly process involves the addition of an active (second) component onto these building blocks. A case in point is the emplacement of a metal onto the support materials in order to obtain so-called supported catalysts. Note that the synthesis of supported catalysts is discussed separately in Chapter 10. 

However, research on carbon nanotubes has opened new avenues in the area of materials science and carbon surface derivatization. Their physical and chemical modifications offer excellent opportunities not only in the characterization and understanding of CNT chemistry, but also in highlighting their potential applications. In the context of this chapter, one important application of CNTs is their use as support for homogeneous catalysts in fact, based on the very few examples published in the literature, this is clearly a very promising area. Furthermore, the potential extrapolation of the CNT derivatization methodologies to more traditional and other recent carbon materials (mesoporous and ordered porous carbon materials) is also one of the major challenges for all researchers who are involved with carbon materials. 

The right choice of a carbon support greatly affects cell performance and durability. The purpose of this chapter is to analyze how structure and properties of carbon materials influence the performance of supported noble metal catalysts in the CLs of the PEMFCs. The review chapter is organized as follows. In Section 12.2 we give an overview of carbon materials utilized for the preparation of the catalytic layers of PEMFC. We describe traditional as well as novel carbon materials, in particular carbon nanotubes and nanofibers and mesoporous carbons. In Section 12.3 we analyze properties of carbon materials essential for fuel cell performance and how these are related to the structural and substructural characteristics of carbon materials. Sections 12.4 and 12.5 are devoted to the preparation and characterization of carbon-supported electrocatalysts and CLs. In Section 12.6 we analyze how carbon supports may influence fuel cell performance. Section 12.7 is devoted to the corrosion and stability of carbon materials and carbon-supported catalysts. In Section 12.8 we provide conclusions and an outlook. Due to obvious space constraints, it was not possible to give a comprehensive treatment of all published data, so rather, we present a selective review and provide references as to where an interested reader may find more detailed information. 

In this study, we will focus our attention mostly on 7-AI2O3, Si02, mesoporous silica and active carbon as support materials. Their respective surface area and porosity are reported in Table 18.2. 

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