| AVS 54th International Symposium | |
| Surface Science | Tuesday Sessions |
| Session SS1-TuA |
| Session: | Bimetallics and Alloys |
| Presenter: | T. Rahman, University of Central Florida |
| Authors: | T. Rahman, University of Central Florida S. Stolbov, University of Central Florida M. Alcantara-Ortigoza, University of Central Florida |
| Correspondent: | Click to Email |
Proton exchange fuel cells are promising tools for hydrogen economy. However, CO traces which are inevitably present, block active sites of the Pt anode and hence poison its reactivity. Recently, Ru nanoparticles with submonolayer Pt coverage are found1 to be much more tolerant to CO than commercial catalysts. To understand the rationale for this tolerance, we have performed density functional theory based calculations of the energetics of adsorption and diffusion of CO on Pt islets on Ru(0001). We find that the total energy of the system gradually decreases as the CO molecule moves from the center of the islets to its edge and further onto substrate. Diffusion barriers for CO are found to be low: 0.06 eV to move from the center of the island to its edge, 0.27 eV to "jump" from the Pt island edge to a neighboring substrate site, and 0.3 eV to move further along the Ru surface. Assuming the pre-factor of CO diffusion to be 1012 sec-1, the diffusion rate at the operating temperature 350K is estimated to be around 107 sec-1. These results suggest that this catalyst is CO tolerant because of the propensity of CO to move from active Pt island site to the Ru substrate. We trace this effect to the features of the local densities of electronic states around the Fermi-level.
1S. R. Brankovic, J. X. Wang, and R. R. Adžic, Electrochem. Solid State Lett.4, A217 (2001).
2 Work supported in part by DOE-BES under grant DE-FG02-07ER15842.