Improving Catalyst-Support Interactions: From Model Systems to High Performing Direct Methanol Fuel Cell Catalysts

Commercialization of fuel cells in general and the Direct Methanol Fuel Cell (DMFC) in particular greatly depends on significant further improvements in catalytic activity and durability. Utilization of the noble metal catalysts is critical and considering cost, availability and demand, needs to be addressed immediately. One very attractive approach that could potentially address these issues is to improve catalyst-support interactions through the introduction of a dopant such as nitrogen, boron or sulfur. A majority of the work using N-doped supports has been focused on Pt catalysts for hydrogen fuel cells. In this talk, we will discuss our recent findings using N-functionalized supports for Pt-Ru catalysts for direct methanol fuel cells. We will discuss various aspects of physical and chemical modification of the carbon supports with nitrogen and their potential effect on the catalyst performance. Initial insight into the role of the nitrogen on the catalyst dispersion, stability and catalytic activity is obtained using model highly-oriented pyrolitic graphite (HOPG) support material. Density Functional Theory (DFT) calculations are used to further our understanding of the possible effect of the nitrogen functionalities and aid in the design of the N-doped high-surface area functional support. Detailed characterization of various high-surface area carbon support materials modified through N ₂ ion implantation will be presented along with the discussion of the level of nitrogen doping, chemical and morphological changes that can be achieved on high surface area materials, such as Vulcan and Graphitic Vulcan. We will show that ion implantation leads to the formation of various functional nitrogen groups, such as pyridinic, pyrrolic and graphitic nitrogen and discuss their potential effect on catalyst performance. For example, we disclose Electron energy loss spectroscopy (EELS) spectral imaging data demonstrating, for the first time, remarkable correlation between the location of Pt catalyst nanoparticles and nitrogen sites.