Advanced nanomaterials for fuel cell catalysts: Characterization of bimetallic nanoparticles

This thesis describes the results of the characterization of bimetallic gold-platinum nanoparticles, which are potential useful catalysts for fuel cell application. The correlation between the electrocatalytic activity and the bimetallic composition of carbon-supported gold-platinum (AuPt/C) nanoparticles (2-4 nm diameters) is investigated for the methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR). The electrocatalytic activities were characterized using cyclic voltammetric and rotating disk electrode techniques, and were also compared with those obtained with Au/C and Pt/C catalysts under the same measurement conditions. The mass activities of the bimetallic catalysts were shown to be not only dependent on the composition, but also the nature of the electrolyte. The bimetallic catalysts with 60∼85% Au were found to exhibit maximum electrocatalytic activities for MOR and ORR in the alkaline electrolytes. The catalysts showed a relatively smooth transition from the low activity of Au to the high activity of Pt in the acidic electrolyte. This remarkable finding suggests a qualitative concurrence with findings from related theoretical modeling and experimental studies, which are discussed in terms of a synergistic activity by the participation of Au in the adsorption of carbon monoxide or oxygenated intermediated species in the MOR or ORR reactions.