The unique rolled graphene structure of carbon nanotubes (CNTs) provides these materials with various properties that could be useful in their application as catalyst supports. For example, properties of CNTs that are of interest in catalyst supports include their good electrical conductivity, excellent mechanical strength, thermal and chemical stability, and special adsorption properties (Serp et al., 2003; Serp and Castillejos, 2010). CNT-supported catalysts have been reported for important liquid-phase (hydrogenation, hydroformylation) or gas-phase (Fischer-Tropsch process, ammonia decomposition, and preferential CO oxidation) reactions (Yin et al., 2004a; Vu et al., 2006b; Trepanier et al., 2009), for supported homogeneous catalysis (hydrogenation and cyanosilylation reactions) (Banerjee and Wong, 2002b; Baleizão et al., 2004), and for electrocatalysis (fuel cell electrodes) (Lee et al., 2006;
15.1 Introduction 409 15.2 Properties of Functionalized Carbon Nanotubes 410 15.3 Methods to Functionalize Carbon Nanotubes 411
15.3.1 Covalent Functionalization 411 15.3.2 Noncovalent Functionalization 414
15.4 Metal Catalyst Loading onto Carbon Nanotubes 415 15.4.1 Grafting of Organometallic Complexes onto Carbon Nanotubes 416 15.4.2 Formation of Metal Nanoparticles on Carbon Nanotube Surface 418 15.4.3 Inclusion of Preformed Metal Nanoparticles onto Carbon Nanotubes 423
15.5 Applications of Carbon Nanotube-Supported Metal Catalysts 426 15.5.1 Supported Homogeneous Catalysis 426 15.5.2 Heterogeneous Catalysis 427 15.5.3 Electrocatalysis 431
15.6 Conclusions 432 References 433
Wang et al., 2008b). However, one of the challenges in the development of CNT-supported catalysts is anchoring of active catalyst phases-most commonly metal or metal oxide nanoparticles-to CNTs because of the strength of the carbon-carbon bond, which makes CNTs very chemical stable, and the hydrophobicity of the graphene ring structure (Jiang and Gao, 2003; Jiang et al., 2003).