Graphitic spherical carbon as a support for a PtRu-alloy catalyst in the methanol electro-oxidation

Spherical carbons were prepared using sucrose as a carbon precursor via hydrothermal method for use as supports for PtRu-alloy catalysts in the methanol electro-oxidation. Spherical carbon particles with an average diameter of 1μm (SC-1) were prepared under static condition (without stirring), while spherical carbon materials with a diameter of 500–600 nm (SC-2) were obtained under dynamic condition (with stirring). A graphitic spherical carbon material (SC-g) was successfully prepared by the addition of Fe salt under dynamic condition. It was revealed that the catalytic action of Fe species during the hydrothermal process was essential for the formation of a graphitic structure of SC-g. The surface areas were found to be 112, 383, and 252 m²/g for SC-1, SC-2, and SC-g, respectively. PtRu nanoparticles were then supported on the spherical carbons by a NaBH₄-reduction method for use in the methanol electro-oxidation. The average metal particle sizes were 3.5, 2.6, and 2.7 nm for PtRu/SC-1, PtRu/SC-2, and PtRu/SC-g, respectively. The PtRu/SC-1 and PtRu/SC-2 showed a lower catalytic performance in the methanol electro-oxidation than the PtRu/Vulcan. However, the PtRu/SC-g exhibited a higher catalytic performance than the PtRu/Vulcan. It is believed that the high graphitic nature of SC-g was responsible for the enhanced catalytic performance of PtRu/SC-g.