Comparative study to understand the intrinsic properties of Pt and Pd catalysts for methanol and ethanol oxidation in alkaline media

The understanding of the intrinsic properties of Pt and Pd is important for the rational design of catalysts for methanol and ethanol oxidation in alkaline media. In this paper, Pd catalysts, Pt catalysts and bimetallic PtPd catalysts supported on nitrogen-doped graphene are investigated. The cyclic voltammograms (CVs) for the bimetallic catalysts in 1 M KOH solution demonstrate the increasing surface composition of Pt versus Pd. The linear sweep voltammetry results show that the onset potential for OH formation on Pt is lower than on Pd, indicating that Pt has a higher affinity for OH than Pd. The CVs recorded for methanol and ethanol oxidation show that ethanol oxidation occurs at lower potentials, suggesting that ethanol is a more active fuel than methanol. Ethanol and methanol oxidation occurs at lower potentials on Pt than on Pd, revealing that Pt is intrinsically more active than Pd. Chronoamperometry results show that the rate of catalysts deactivation during ethanol oxidation is more severe compared with methanol oxidation, especially for catalysts with higher Pt content. The possible reason for the deactivation behaviors is presented and recommendations are given for future catalysts development.