Co/N/C Catalysts on a Vertically Aligned Carbon Support for Oxygen Reduction Reaction

The power output of proton exchange membrane fuel cells with non-precious metal cathode catalysts has been insufficient particular for automobile applications. This is largely due to poor mass-transport properties in the thicker catalyst layers compared to those for the Pt-based catalysts. To improve mass-transport properties, we have fabricated a model catalyst comprising cobalt, nitrogen, and carbon (Co/N/C catalyst) on a vertically aligned carbon nanowall(CNW)-like support. The Co/N/C catalyst was formed by electropolymerization of cobalt-coordinated pyrrole on the CNW support which has better structural stability in water than cabon nanotubes. XPS analysis and electrochemical ORR measurements indicate that the electropolymerized catalyst is likely distributed on the side surfaces of each CNW. At a low catalyst loading, the CNW-supported Co/N/C catalyst showed higher ORR current than a planar carbon-supported Co/N/C catalyst. This is presumably due to improved mass transport properties and/or increased surface area. Further investigation is required to separate these effects.