Design of nanostructured electrocatalysts for direct methanol fuel cells

Abstract

Due to their excellent catalytic activity with respect to methanol oxidation on platinum at low temperature, platinum nanosized catalysts have been a topic of great interest for use in direct methanol fuel cells (DMFCs). Because pure platinum is readily poisoned by CO, a by-product of methanol electrooxidation, and is extremely expensive, a number of efforts to design and characterize Pt-based alloy nanosized catalysts or Pt nanophase-support composites have been attempted in order to reduce or relieve the CO poisoning effect. In this review paper, we summarize these efforts based upon Our recent research results. The Pt-based nanocatalysts were prepared through chemical synthesis and thin-film technology, and were characterized using a variety of analyses. According to bifunctional mechanism, it was concluded that good alloy fori-nation with a second metal (e.g., Ru), as well as the metallic state and the optimum portion of Ru in the anode catalyst, contribute to the enhanced catalytic activity for methanol electrooxidation. In addition, we found that the modified electronic properties of platinum in Pt alloy electrodes, as well as the surface and bulk structures of Pt alloys in suitable compositions, could be attributed to the higher catalytic activity for methanol electrooxdation. The proton conducting contribution of nanosized electrocatalysts should also be considered to be excellent in methanol electrooxidation (spillover effect). Finally, we confirmed the ensemble effect, which combined all of the effects listed above, in Pt-based nanocatalysts; PtRuRhNi and PtRuWO3, especially, contribute to an enhanced catalytic activity.