Preparation of PtRu nanoparticles on various carbon supports using surfactants and their catalytic activities for methanol electro-oxidation

Abstract

In the anodes of direct methanol fuel cells (DMFCs), Pt poisoning by CO adsorption during methanol electro-oxidation has been a serious problem. Efforts to overcome or minimize this obstacle have largely involved investigations of PtRu bimetallic catalysts. In order to prepare fine PtRu alloyed hydrosols, we used non-ionic surfactants including L121, Pluronic P123, P65, Brij 35, and Tween 20 as stabilizers in this study. The sizes of the prepared metal particles change with the surfactant used. The finest metal hydrosol is obtained when Pluronic P123 and P65 are used. The resulting metal hydrosols with Pluronic P123, Brij 35 and Tween 20 are supported on Vulcan XC-72R. PtRu/XC-72R prepared with Pluronic P123 exhibits the best catalytic activity due to better dispersion of the alloyed metal. To improve further the activity of the PtRu catalyst, the commercial Vulcan XC-72R is replaced with carbon spherule (CS), a home-made carbon support. Electrochemical analyses such as cyclic voltammetry and galvanostatic-polarization tests are performed to evaluate the prepared catalyst. PtRu/CS has a superior performance to PtRu/XC-72R in methanol electro-oxidation when Pluronic P123 is employed as the stabilizer. The higher conductivity and larger inter-particle space of the CS appear to facilitate methanol electro-oxidation.