Methanol Oxidation Activity of Nanosized PtRu Catalysts and Their Microstructures

摘要

The nanosized PtRu catalyst was synthesized via the polyol process and electroless plating method. The size of the catalyst was decreased to 2 nm with the addition of phosphorus (P) in order to improve the methanol oxidation reaction (MOR) activity. The highest MOR activity was obtained with the bulk and surface compositions of Pt_(73)Ru_(27) and Pt_(53)Ru_(47), respectively. The XRF, Cu under potential deposition/Cu stripping and EXAFS analyses revealed that the Pt-enriched core/Ru-enriched shell microstructure was formed in the PtRuP catalyst with the particle size of 2 nm. This Pt-dominant bulk composition, Pt_(73)Ru_(27), was required to make the surface composition close to the active composition of Pt_(50)Ru_(50) due to the preferential reduction of Pt cation. The difference in the reduction potential of Pt and Ru cations was decreased from 0.42 V to 0.31 V with the addition of the chelating ligand. This decrease advanced the mixing state of the Pt and Ru atoms in the whole region of the catalyst, resulting in the higher MOR activity.