Formic acid oxidation on Pt/Ru nanoparticles: Temperature effects

The formic acid oxidation on Pt/Ru nanoparticles in acid solution over the temperature range 298-333 K has been studied by thin-film rotating disk method (RDE). Transmission electron microscopy in combination with scanning tunneling microscopy was used to determine the size (4.3 +/- 0.3 nm) and shape (cuboctahedral) of the particles. Kinetic analysis revealed that at elevated temperatures (313 K, 333 K) the reaction rate is much higher than at room temperature (295 K), indicating that formic acid oxidation on supported Pt/Ru catalyst is a highly activated process. Based on experimental kinetic parameters we propose that the HCOOH oxidation on the PtRu alloy most likely follows a dual pathway, but the branching ratio is still very high, i.e. Pt-like. The principal effect of opening the dehydration channel at steady-state (via the presence of Ru in the surface) is to lower the coverage of COads on Pt sites and permit the dehydrogenation path to increase in rate.