Experiment and Theory of Fuel Cell Catalysis: Methanol and Formic Acid Decomposition on Nanoparticle Pt/Ru

Abstract

This study seeks to explore the effects of the electronic structure of Pt/Ru alloy nanoparticles on reactivity of small organic molecules of relevance to fuel cell applications through the combined use of synchrotron radiation photoelectron spectroscopy and electrochemistry. Platinum core-level binding energies were found to increase linearly with the addition of ruthenium. This effect is a product of lattice strain and charge transfer, and is explained in terms of the d-band center theory proposed by Nørskov and co-workers (Hammer, B.; Nørskov, J. K. Surf. Sci. 1995, 343, 211). In the course of the study of electrooxidation of methanol we have found that it is very difficult, if not impossible, to separate the effects of the bifunctional mechanism and the electronic structure effects that might play a role in the activity. However, data for electrooxidation of formic acid, when studied at a short reaction time (where the indirect reaction pathways and poisoning intermediates are assumed to play a negligible role), demonstrate a definitive contribution from electronic structure on the reactivity. The reactivity of the Pt/Ru nanoparticles toward formic acid electrooxidation is discussed in terms of the d-band center theory.