Graphene-Supported Platinum and Platinum-Ruthenium Nanoparticles for Fuel Cell Applications

Abstract

As one of the most promising alternative energies, fuel cells have been receiving increased attention recently due to the depletion of fossil fuels and the increase in environmental pollution. Among different types of fuel cells, direct ethanol fuel cells (DEFCs) and direct methanol fuel cells (DMFCs) are excellent power sources due to their high energy density, low pollutant emission, low operating temperature, and ease of handling liquid ethanol/methanol fuel (Lamy et al., 2002; Long et al., 2000; Maillard et al., 2003). However, critical obstacles remain that inhibit broad applications of DEFCs and DMFCs, including low electrocatalytic activity of anode/cathode electrodes and the high cost of noble metal, platinum (Pt)-based catalysts. In order to enhance catalytic activity and to reduce the usage of Pt-based catalysts, one strategy is to explore novel carbon materials as catalyst supports and to effectively disperse Pt-based particles on these supports (Chen et al., 2007; Sanganna Gari et al., 2010; Girishkumar et al., 2006; Halder et al., 2009; Maiyalagan, 2008; Selvaraj & Alagar, 2007; Rajesh et al., 2003; Tang et al., 2004; Tsai et al., 2006; Zhao et al., 2004). Vulcan XC-72R carbon black has been the most widely-used catalyst support for the preparation of fuel cell catalysts because of its exceptional electronic conductivity and surface area (Guo et al., 2008; Lin et al., 2005; Maiyalagan et al., 2005). During the past several years, a few research groups have investigated graphene, one type of novel carbon nanostructures, as a catalyst support and have demonstrated that graphene can improve the electrocatalytic activity of Pt nanoparticles more effectively for methanol and ethanol oxidation than Vulcan XC-72R carbon black (Dong et al., 2010; Seger et al., 2009; Yoo et al., 2009). In this chapter, a series of atomic force microscopy (AFM) and electron microscopy techniques, including scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM), were employed to characterize the morphology of Pt nanoparticles, platinum-ruthenium (Pt-Ru) nanoparticles, and graphene sheets as well as the distribution of Pt and Pt-Ru nanoparticles on the graphene supports. Effects of graphene supports on electrocatalytic activity of Pt and Pt-Ru nanoparticles for methanol and ethanol oxidations were investigated using cyclic voltammetry. In comparison to Vulcan XC-72R