关键词：环境与资源；燃料电池；化学吸附；密度泛函方法
摘 要：We have studied the effect of nanostructuring in Pt monolayer model electrocatalysts on a Rh(111) single-crystal substrate on the adsorption strength of chemisorbed species. In situ high energy resolution fluorescence detection x-ray absorption spectroscopy (HERFD XAS) at the Pt L3 edge reveals characteristic changes of the shape and intensity of the “white-line” due to chemisorption of atomic hydrogen (Had) at low potentials and oxygen-containing species (O/OHad) at high potentials. On a uniform, two-dimensional Pt monolayer grown by Pt evaporation in ultrahigh vacuum (UHV), we observe a significant destabilization of both Had and O/OHad due to strain and ligand effects induced by the underlying Rh(111) substrate. When Pt is deposited via a wetchemical route, by contrast, three-dimensional Pt islands are formed. In this case, strain and Rh ligand effects are balanced with higher local thickness of the Pt islands as well as higher defect density, shifting H and OH adsorption energies back towards pure Pt. Using density functional theory (DFT) we calculate O adsorption energies and corresponding local ORR activities for fcc threefold hollow sites with various local geometries that are present in the three-dimensional Pt islands.