Enhanced catalytic performance of a Pt-xCeO2/Graphene catalyst for DMFCs by adjusting the crystal-plane and shape of nanoscale ceria

Abstract

Oxygen storage capacity is influenced by the morphology and crystal-plane(s) of CeO₂, which can thus affect the ability of this material to oxidise carbon monoxide. To investigate the effect of different morphologies/crystal-planes of CeO₂ on the electrocatalytic performance of DMFCs (Direct Methanol Fuel Cell), three different types of CeO₂ nanocrystals with different crystal-planes were synthesised and later assembled into Pt–xCeO₂/Graphene composites with graphene and Pt nanoparticles as the electrocatalyst for DMFCs. According to the HRTEM images, the original morphology and crystal-plane structures of CeO₂ are essentially maintained in the three types of Pt–xCeO₂/Graphene composite catalysts investigated in this work. The catalytic performance of the Pt–xCeO₂/Graphene composites for methanol electrocatalytic oxidation was investigated by a series of electrochemical measurements. Compared with the other catalysts, Pt–rCeO₂/Graphene demonstrates superior catalytic activity (onset potential: 0.15 V) and the strongest resistance to poisoning by carbonaceous species (I_f/I_b: 2.11). The results of H₂-TPR shows that rCeO₂ with the {110} facet has the best surface reducibility among the xCeO₂ with different facets being investigated, which provides a rationale for the superior performance of the Pt–rCeO₂/Graphene catalyst. This study indicates that metallic oxides with a suitable crystal plane and shape can effectively enhance the electrocatalytic performance of Pt-based catalysts for methanol electrooxidation.