Characterization and enhancement of carbon nanotube-supported PtRu electrocatalyst for direct methanol fuel cell applications

In this study, a carbon nanotube-supported PtRu electrocatalyst (PtRuCNT) was prepared, characterized and investigated for methanol electro-oxiclation by catalytic activity enhancement using an electrochemical treatment. From XPS analyses, the as-prepared catalyst was found to mainly composed of Pt(O)/Pt(II) states for the Pt element and Ru(O)/Ru(IV) states for the Ru element. When the electrocatalyst was subjected to an enhancement treatment, the Ru(IV) state increased substantially from 29.50% to 44.11%. Both CO-stripping experiments and open-circuit cell voltage measurements indicated that the treated PtRuCNT has given rise to an improved performance on methanol electrooxidation caused mainly by the increase of the Ru(IV) state in this particular case. The single-cell test also revealed that a direct methanol fuel cell (DMFC) can be put into its full operation in a short time. A direct application of this finding is to significantly shorten the activation time of a new DMFC stack. However, the electrochemically treated PtRuCNT catalyst still needs a continuous enhancement mechanism to sustain its enhanced activity. A promotional model is proposed to explain the phenomenon observed and a remedial approach is also Suggested to solve the problem for practical applications. (C) 2008 Elsevier B.V. All rights reserved.