Nitrogen-doped graphene prepared by low-temperature thermal treatment as an electrocatalyst support for methanol oxidation

In this study, functionalized graphene is used as a carbon-based material to support platinum-ruthenium bimetallic nanoparticles and to improve methanol oxidation reaction activity due to the enhanced physical and electrical properties of graphene. First, surface oxidation is used for creating oxygen functional groups, and then nitrogen doping by thermal treatment with ammonia as the nitrogen precursor. Platinum-ruthenium alloy nanoparticles are dispersed by the impregnation reduction method on the support materials. The final nanocomposite samples contain 8% of oxygen and 3% of nitrogen. Compared to PtRu/GNS and PtRu/CB, the PtRu/NO-GNS catalyst indicates 1.25 and 1.3 times higher surface area, and 2.3 and 4 times higher electrochemical surface area, respectively. The highest methanol oxidation current density of 305 mA/mg and 262 mA/mg is obtained for platinum-ruthenium supported on nitrogen-doped graphene and nitrogen-doped oxidized graphene, which is 2.9 and 2.5 times higher than that for PtRu/GNS, respectively. It is revealed that the nitrogen-doped samples have shown greater activity and long-term stability than other electrocatalysts, including the widely used carbon black supported catalyst. Hence, this work reports the performance of an efficient alternative electrocatalyst with practical application in direct methanol fuel cells.