Highly alloyed PtRu black electrocatalysts for methanol oxidation prepared using magnesia nanoparticles as sacrificial templates

Abstract

Synthesis of small particle size, highly alloyed PtRu black catalysts for application in direct methanol fuel cells remains a substantial challenge. In this work, PtRu (1:1) black catalysts have been synthesized using Pt carbonyl complex and RuCl3 as initial precursors and magnesia nanoparticles as sacrificial templates. Magnesia is used to prevent the aggregation of synthesized PtRu nanoparticles during heat treatment, and thus promoting the controllable formation of PtRu black of high alloy composition and small particle size. X-ray diffraction shows that the PtRu black nanoparticles have a single-phase face-centered cubic structure and that the degree of alloying increases with treatment temperature. The mean particle size of the PtRu black catalysts, after heat-treatment from 250 to 300 °C, is found to be ca. 3 nm, only slightly larger than that of commercial Johnson-Matthey PtRu black, but more highly alloyed. Electrochemical measurements indicate that the catalytic activity for methanol oxidation on in-house prepared PtRu black catalysts is about twice that of the commercial product, with greater durability, indicating that the degree of alloying between Pt and Ru plays an important role in improving both catalytic activity and durability of the catalysts when used for methanol oxidation.