Catalysis Today, Vol.312, 126-131, 2018
Probing the edge effect on the ORR activity using platinum nanorods: A DFT study
The overall activity of the oxygen reduction reaction (ORR) over multifaceted nanoparticles is typically interpreted as a linear combination of the ORR activity of different facets and surface site-types present on these particles. It is thus implicitly assumed that (i) edge effects are local phenomena and (ii) different facets are kinetically isolated, i. e. transfer of adsorbates over the edge is kinetically limited. Here we use rhombic nanorod models and density functional theory, with atomic O as a probe, to investigate these assumptions. The adsorption energy of atomic O was found to be virtually independent of the distance from the nanorod edge beyond the edge atomic row, indicating a localized edge effect. A kinetic connection between two adjacent facets however cannot be ruled out. The connection between the adjacent Pt{100} and Pt{111} facets, through atomic O diffusion, is kinetically more favorable at 1.0 ML edge coverage compared to 0.5 ML edge coverage as a result of repulsive lateral interactions between co-adsorbed O atoms and the corresponding flattening of the potential energy surface.