| AVS 55th International Symposium & Exhibition | |
| Surface Science | Monday Sessions |
| Session SS+NC-MoM |
| Session: | Catalysis and Alloy Formation |
| Presenter: | D.E. Starr, Brookhaven National Laboratory |
| Authors: | D.E. Starr, Brookhaven National Laboratory H. Bluhm, Lawrence Berkeley National Laboratory |
| Correspondent: | Click to Email |
Carbon supported PtRu alloy particles are currently used as the anode catalyst in proton exchange membrane fuel cells. Small amounts of CO, in the ppm concentration range, present in the H2 fuel are known to poison the catalyst. The role of Ru is to increase the CO tolerance of the catalyst. Since both Pt and Ru are expensive metals, understanding the catalyst’s susceptibility to CO poisoning and the function of Ru in reducing this susceptibility are important aspects for cost reduction of proton exchange membrane fuel cells. The increased CO tolerance of these catalysts has been attributed either to CO oxidation by adsorbed OH groups on Ru or by weaker adsorption of CO on the alloy surface than either of the pure metals leading to a decrease in the steady-state coverage of CO. Direct proof of the mechanism for the alloy’s increased CO tolerance requires detailed knowledge of the surface composition under reaction conditions. As a first step towards gaining this knowledge, we have used the Ambient Pressure Photoemission Spectroscopy experiment at Beamline 11.0.2 of the Advanced Light Source to study the adsorption of CO onto Ru(0001) and PtRu near surface alloys on Ru(0001) at 300 K and pressures up to 0.5 torr. The results of this study show that at 300 K the coverage of CO on the Ru(0001) surface saturates at ~ 1x10-6 torr and remains constant up to 0.5 torr. At pressures greater than 10-2 torr a second peak appears in the O1s spectra indicating the presence of a second CO species. Comparison of these results to those obtained with a PtRu surface alloy formed on the Ru(0001) surface will be presented.