Hydrogen adsorption and coadsorption with CO on well-defined bimetallic PtRu surfaces––a model study on the CO tolerance of bimetallic PtRu anode catalysts in low temperature polymer electrolyte fuel cells

• Published in: Surface science 2003-09, Vol.541 (1), p.137-146
• Main Authors: Diemant, T, Hager, T, Hoster, H.E, Rauscher, H, Behm, R.J
• Format: Article
• Language: English
• Subjects: Adsorption and desorption kinetics; evaporation and condensation; Adsorption kinetics; Alloys; Carbon monoxide; Condensed matter: structure, mechanical and thermal properties; Deuterium; Exact sciences and technology; Hydrogen molecule; Metallic surfaces; Physics; Platinum; Ruthenium; Scanning tunneling microscopy; Solid-fluid interfaces; Surface electronic phenomena (work function, surface potential, surface states, etc.); Surface stress; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thermal desorption
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/S0039-6028(03)00915-4

The influence of PtRu surface alloy formation and of coadsorbed CO on the adsorption/desorption characteristics of hydrogen on bimetallic PtRu surfaces was investigated by temperature programmed desorption, using a 40% Pt containing PtRu surface alloy pseudomorphic on a Ru(0 0 0 1) surface with an almost statistical distribution of Pt surface atoms as substrate. Alloy formation leads to a significant broadening of the desorption peak compared to pure Ru, together with a considerable down-shift in the onset of desorption. This trend is even more pronounced in the presence of coadsorbed CO. The weakening of the hydrogen adsorption bond is attributed mainly to strain effects, imposed by the considerable compression of the pseudomorphic Pt as compared to bulk Pt(1 1 1). Finally we discuss the implications of these results for the mechanistic understanding of the improved performance of PtRu anode catalysts in reformate operated polymer electrolyte fuel cells.