More active PtRu/C catalyst for methanol electrooxidation by reversal of mixing sequence in catalyst preparation

A carbon-supported PtRu/C catalyst (PtRu-2/C) was prepared by a simple reversal of the order of mixing in catalyst preparation: adding the metal precursor salts to a carbon slurry of NaBH4 instead of adding NaBH4 to a carbon slurry of the metal precursor salts (PtRu-1/C), as is more commonly done. The catalysts were characterized by thermogravimetric analysis, transmission electron microscopy and X-ray photoelectron spectroscopy. Evaluation of catalytic activities by cyclic voltammetry, CO stripping voltammetry, and chronoamperometry showed that PtRu-2/C had higher specific mass activity and greater CO tolerance in room temperature methanol electrooxidation reaction. Electrochemical impedance spectroscopy also confirmed that the impedance arising from CO adsorption was lower in the case of PtRu-2/C. The enhanced operational performance of PtRu-2/C is attributed to the presence of mixed active phases although the exact composition of the mixed phases has yet to be determined.