Speaker
Description
The development of efficient fuel cells is a promising strategy to diminish fossil fuel consumption. A major drawback of state-of-the-art proton exchange membrane fuel cells (PEMFCs) is CO poisoning of the platinum catalyst.[1] CO molecules present in the fuel preferentially adsorb to Pt nanoparticles, thereby blocking the active sites and degrading the cell’s performance. Several Pt alloys are known for an enhanced tolerance to the CO poisoning, improving the fuel cell performance. [2] The physical mechanism responsible for the tolerance remains a subject of debate, being ascribed either to an alteration of the Pt electronic structure upon alloying or to a bi-functional mechanism, in which OH groups interact with CO and form CO2 and H2 thereby regenerating the active sites.[2] In this contribution we discuss the influence of Nb, Mo, Sn and Ag dopant atoms on the CO adsorption on PtN+ (N=13-23) clusters. Clusters can be studied in molecular beams and high vacuum conditions, allowing a perfect control over the particle’s mass and excluding reactions with unknown molecules.[3,4] Combined mass spectrometric experiments and density functional theory calculations show a significant reduction in the reactivity for Nb and Mo doped clusters, which is attributed to electron transfer from the dopant to the Pt atoms and the concomitant reduction of the CO binding energies. On the other hand Sn and Ag doping has a limited effect on the CO adsorption. Analysis of the density of states demonstrates a correlation of dopant induced changes in the electronic structure with the enhanced tolerance to CO poisoning.
[1] J. Baschuk, and X. Li, Int. J. Energy Res. 2001, 25, 695. [2] S. Ehteshamia and S. Chan, Electrochim. Acta 2003, 93, 334. [3] S. M. Lang et al., Angew. Chem. Int. Ed. 2010, 49, 980. [4] V. Kaydashev, E. Janssens and P. Lievens, Int. J. Mass Spectrom. 2015, 379, 133.
