Synthesis and characterization of carbon nanotube supported nanoparticles for catalysis
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This dissertation describes the synthesis and characterization of nitrogen doped carbon nanotube (NCNT) supported nanoparticles for catalysis, specifically, the cathodic oxygen reduction reaction (ORR) in fuel cells. Strategies for synthesis of mono- and bimetallic nanoparticle catalysts through dendrimer based templating techniques and with the aid of metal organic chemical vapor deposition (MOCVD) precursors and efficient assembly protocols of the catalysts with the NCNTs are discussed in detail. Physicochemical properties of the NCNTs and NCNT supported catalysts were characterized using a host of tools including scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, x-ray photoelectron spectroscopy (XPS), thermo gravimetric analysis, BET surface area and pore size analysis and electrochemical techniques including cyclic voltammetry, chronocoulometry, chronoamperometry and rotating disk electrode voltammetry. Chapter 1 serves as a general introduction and provides a brief overview of challenges associated with the synthesis, characterization and utilization of graphitic carbons and graphitic carbon supported catalysts in heterogeneous catalysis. Chapter 2 provides an overview of the synthesis and characterization of systematically doped iron and nickel catalyzed NCNTs in an effort to understand the effect of nitrogen doping on ORR. Chapter 3 describes the use of NCNTs as supports for dendrimer templated nanoparticle catalysts for ORR. A facile synthetic strategy for the immersion based loading of catalysts onto NCNTs by spontaneous adsorption to achieve specific catalyst loadings is explored. Chapter 4 details the loading of monodisperse Pt, Pd and PtPd catalysts on the as synthesized NCNTs using MOCVD precursors. The MOCVD route offers promise for direct dispersion and activation of ORR catalysts on NCNT supports and eliminates a host of problems associated with traditional solvent based catalyst preparation schemes. Chapter 5 details future directions on a few topics of interest including efficient electrodeposition strategies for preparing NCNT supported catalysts, studies on PtCu catalysts for ORR and finally prospects of using NCNT supported catalysts in fuel cell applications.