Physical characterization electrocatalysts

In this chapter we review studies, primarily from our laboratory, of Pt and Pt-bimetallic nanoparticle electrocatalysts for the oxygen reduction reaction (ORR) and the electrochemical oxidation of H2 (HOR) and H2/CO mixtures in aqueous electrolytes at 274—333 K. We focus on the study of both the structure sensitivity of the reactions as gleaned from studies of the bulk (bi) metallic surfaces and the resultant crystallite size effect expected or observed when the catalyst is of nanoscale dimension. Physical characterization of the nanoparticles by high-resolution transmission electron microscopy (HRTEM) techniques is shown to be an essential tool for these studies. Comparison with well-characterized model surfaces have revealed only a few nanoparticle anomalies, although the number of bimetallics... 

The physical characterization of electrocatalysts is very important for several areas of research (1) preparing new types of electrocatalysts wifli high activity and high selectivity, (2) recognizing electrocatalyst structures, and (3) investigating flie mechanisms of catalysts and certain additives. 

Table 16.2. Physical characterization of PtRu alloy electrocatalysts [43]. (Reprinted from Ralph TR, Hogarth MP. Catalysis for low temperature fuel cells, part II the anode challenges. Plat Met Rev 2002 46(3) 117-35, 2002. With permission from Platinum Metals Review.)...

Markovic NM, Radmilovic V, Ross PN. 2003. Physical and electrochemical characterization of bimetallic nanoparticle electrocatalysts. In Wieckowski A, Savinova E, Vayenas C, eds. Catalysis and Electrocatalysis at Nanoparticle Surfaces. New York Marcel Dekker, pp. 311-342. 

Lalande G, Cote R, Tamizhmani G, Guay D, Dodelet JP. 1995. Physical, chemical and electrochemical characterization of heat-treated tetracarboxylic cobalt phthalocyanine adsorbed on carbon black as electrocatalyst for oxygen reduction in polymer electrolyte fuel cells. Electrochim Acta 40 2635-2646. 

As a demanding reaction, it is very sensitive to the structural and compositional details of the anode materials. For this reason, research on anodes for O2 evolution calls for close characterization of electrocatalysts, especially from the point of view of materials chemistry and physics. 

Chapter 4, by Batzill and his coworkers, describes modern surface characterization techniques that include photoelectron diffraction and ion scattering as well as scanning probe microscopies. The chapter by Hayden discusses model hydrogen fuel cell electrocatalysts, and the chapter by Ertl and Schuster addresses the electrochemical nano structuring of surfaces. Henry discusses adsorption and reactions on supported model catalysts, and Goodman and Santra describe size-dependent electronic structure and catalytic properties of metal clusters supported on ultra-thin oxide films. In Chapter 9, Markovic and his coworkers discuss modern physical and electrochemical characterization of bimetallic nanoparticle electrocatalysts. 

Physical and Electrochemical Characterization of Bimetallic Nanoparticle Electrocatalysts... 

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