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-oxidation by catalytic activity enhancement using an electrochemical treatment. From XPS analyses, the as-prepared catalyst was found to mainly composed of Pt(0)/Pt(II) states for the Pt element and Ru(0)/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 electro-oxidation 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.