Radiation 2006. In association with the Polymer Division, Royal Australian Chemical Institute. Incorporating the 21st AINSE Radiation Chemistry Conference and the 18th Radiation Biology Conference, conference handbook

Full text: It is well known that the catalytic performance of direct methanol fuel cells (DMFC) strongly depends on the size of the precious metal catalyst particles. Composite Pt-Ru catalyst particles have attracted a considerable amount of attention in recent years as the ruthenium helps to protect the platinum catalyst from CO poisoning. Conventional preparation techniques often do not provide adequate and effective control of particle size and usually involve undesirable stabilizers for fuel cell application. It is well known that ultrasonic irradiation of aqueous noble metal solutions results in nanometer sized metal colloids. In our study, Pt-Ru composite nanoparticles were synthesized by ultrasound induced reduction of aqueous solutions K2PtCl4 and RuCl3 using a 213kHz ultrasonictor. After 5 hours of sonication, the absorbance bands arising from Pt(II) and Ru(III) disappeared and the composite Pt-Ru nanoparticles were formed. The reduction of Ru(III) in the composite system was accelerated dramatically, compared with the reduction of Ru(III) by itself with the sonication time decreasing from 12 hours to 5 hours. It has been concluded that Pt nanoparticles, which are formed first play an important role in catalysing the formation of Ru nanoparticles. TEM images of the Pt and Ru particles in the composite colloid indicate typical diameters less than 10nm