ABSTRACT
During the past century, chemists have primarily focused on making and breaking strong covalent bonds.With this approach, it is possible to combine atoms into molecules and extended structures with nearly arbitrary atomic scale configurations (Service, 2005). Molecules of increased size and complexity require more demanding synthetic methods and for many years, meso-or macro-scale designed configurations, generated by molecular assembly, had limited accessibility. However, chemists have not viewed hydrogen bonds, Van der Wall’s forces, and medium to long range electrostatic forces, all of which are much weaker than covalent bonds, as chemical glue for assembling molecules into materials (Fan et al., 2008). This is in spite of the fact that nature is built on this approach; nearly all that surrounds us, from cells to trees, are knit together usingweak interactions betweenmolecules. The formation process formany of themeso-structuredmaterials, whereby a collection of small molecules, electrolytes, polymers, and co-solvents spontaneously combine into larger, well-defined supra-molecular assemblies or aggregates due to the weak forces, has historically been termed by chemists and materials scientists as “self-assembly”, “cooperative self-assembly”, or “molecular assembly”. Over the past two decades, researchers have made large advances in understanding the basic rules of molecular assembly, as well as in developingmethods to simultaneously control intermolecular interactions and reaction kinetics to create material systems with hierarchical ordering and complexity (Davis, 2002). Methodologies, which make use of molecular assembly, have been recognized as the most promising approach for the fabrication of a wide variety of meso-structured materials. At this juncture, it is important to note that platinum-supported carbon catalysts are generally
used as electrode materials, e.g., methanol oxidation reaction at the anodes of direct methanol fuel cells (DMFCs) and oxygen reduction reaction at the cathodes of proton exchange membrane fuel cells (PEMFCs). These systems have received considerable attention as clean energy sources for various applications (Winter and Brodd, 2004). However, in order to achieve high dispersion, good stability, effective utilization and stupendous activity of platinummetal, porous carbonswith ordered pore structure, high surface area, nano-scale morphology, tunable pore characteristics with varied surface functionality, and good electric conductivity are highly desirable for electrocatalysts (Dicks, 2006; Gasteiger and Markovic´, 2009). In this regard, the most commonly used electro-catalyst, both for cathode and anode, is platinum supported on carbon blacks (Escudero et al., 2002; Lizcano-Valbuena et al., 2003; Kim et al., 2003; Tian et al., 2004). However, it is necessary to obtain a more effective catalyst, both in catalytic performance and electronic conductivity. To achieve a higher efficiency of the electro-catalysts, platinum has to be well dispersed on the support. For this reason, it is desirable that the supportmaterial provides a suitable specific area and surface chemistry as well as good electrical conductivity. In this chapter, we address such issues in a greater detail by taking into account of our recent work (Kuppan, 2014; Kuppan and Selvam, 2012; Selvam and Kuppan, 2012) on nano-platinum-supported mesoporous carbons such as NCCR-41, CMK-3, NCCR-11 and CMK-1 for DMFCs.
