Formic Acid Oxidation at Ru@Pt Core-Shell Nanoparticles

Formic acid oxidation has been investigated at Ru@Pt core-shell nanoparticles for Pt coverages ranging from 0.4 to 1.9 monolayers (ML), in order to determine how the bi-functional and electronic effect of the Ru core and compression of the Pt lattice influence activity. By comparing voltammetric results with those for CO stripping and bulk oxidation, it has been shown that the electronic effect of the Ru core on CO oxidation is the dominant factor influencing formic acid oxidation. Thus, the indirect pathway through adsorbed CO begins at the lowest potential for sub-monolayer Pt coverages, and the formic acid oxidation rate increases as the Pt coverage is increased towards one monolayer. However, the electronic effect of the Ru becomes muted as a second Pt layer is added, CO oxidation is shifted to higher potentials and formic acid oxidation activity drops. The optimum coverage of Pt depends on a balance between the electronic effects of the Ru core on the promotion of CO oxidation and inhibition of formic acid oxidation through the direct pathway that does not produce adsorbed CO. Thus, a coverage of 0.85 ML Pt provided the best activity for 0.5 M formic acid, while 1.3 ML gave a particularly high activity for 2 M formic acid at low potentials.