Orientation-Dependent Hindrance to the Oxidation of Pd–Au Alloy Surfaces

Abstract

Oxidation of monometallic Pd and bimetallic Pd3Au alloy surfaces are observed by in situ ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) at an elevated pressure (100 mTorr O2 ambient). It is directly evidenced that the alloying with Au hinders the surface oxidation of Pd3Au surfaces compared with monometallic Pd surfaces. Remarkably, the oxidation behavior is clearly different between Pd3Au­(111) and (100) surfaces. The (100) surface has a relatively Pd-rich surface composition, and the surface oxide layer is formed, whereas the (111) surface has a Au-rich composition, and the surface oxidation is quite limited. A combined approach of experimental and theoretical techniques reveals that Pd/Au surface composition and atomic arrangement are key factors determining the oxidation behavior.

Fabrication of a NiFe Alloy Oxide Catalyst via Surface Reconstruction for Selective Hydrodeoxygenation of Fatty Acid to Fatty Alcohol

“…A four-layer p (4 × 4) NiFe (101) slab with 20 Å vacuum region was built, in which the bottom two layers were fixed at the optimized bulk positions. The NiFe (101) surfaces with different degrees of oxidation are modeled by adsorption of different amounts of oxygen atoms on the surface based on the previous study …”

“…The NiFe (101) surfaces with different degrees of oxidation are modeled by adsorption of different amounts of oxygen atoms on the surface based on the previous study. 49 Adsorption energies of reactant and intermediate products were calculated by the following formula…”