Particle growth behavior of carbon-supported Pt,Ru,PtRu catalysts prepared by an impregnation reductive-pyrolysis method for direct methanol fuel cell anodes

摘要

Carbon-supported Pt,Ru,and binary PtRu catalysts were prepared by an impregnation-reductive pyrolysis method at various temperatures,with Pt(NH_3)_2(NO_2)_2 and Ru(NO_3)_3 as precursors.The effect of the reductive pyrolysis temperature on the structure of the metal particles and its relationship to the electrocatalytic activity toward methanol and preadsorbed carbon monoxide(CO_ad)oxidation was examined.The decomposition temperature of the Pt_50Ru_50 mixed precursor shifted to a temperature lower than that of the Ru single-source precursor.High-resolution scanning electron microscopy,X-ray diffraction,and CO_ad stripping voltammetry of Pt/C and Ru/C indicated that Ru nanoparticles tend to grow drastically when the pyrolysis temperature is increased,whereas Pt nanoparticles are more resistant to particle growth.Scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy analysis showed that there is a slight compositional variation between individual nanoparticles,depending on the particle size.The Pt_50Ru_50/C catalyst prepared at 200 deg C exhibited the maximum electrocatalytic activity toward methanol oxidation per mass of PtRu,which is discussed based on the appropriate balance of precursor decomposition and particle growth.