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

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 (If/Ib: 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.