Electronic changes at the platinum interface induced by bismuth and tellurium adatom adsorption

Not a Mere Decoration: Impact of Submonolayer Coverages of Nickel on Fundamental Properties of Platinum

“…Nevertheless, it is difficult to predict the magnitude of these changes. In the case of Bi adatoms, an element with a similar electronegativity to the one of Ni, calculated ΔΦ is larger than the values given in Table , −0.72, −0.44, and – 0.22 eV for Pt(111), Pt(100), and Pt(110), respectively, highlighting the influence of the distribution of valence electrons and the atomic radius.…”

“…Changes in Φ upon adatom adsorption open a possibility to tune catalytic properties of platinum-based materials, especially for structure-sensitive surface reactions. − These changes follow the same tendency regarding the magnitude of charge transfer and distance from the surface (i.e., surface dipole) discussed above, because similar tendencies have been reported for other adatoms on Pt single crystal surfaces . Nevertheless, it is difficult to predict the magnitude of these changes.…”

“…This difference in the bonding character may appear because of the more delocalized nature of valence electrons in Ni due to the partially filled d -orbitals and the smaller Ni atomic radius, r Ni = 124.6 pm, closer to r Pt = 138.5 pm, than r Bi = 154.5 pm, which allows a reduction of ca. 20 to 50% in d Ni–Pt relative to d Bi–Pt , depending on the surface plane. It appears that these additional parameters, distribution of valence electrons and atomic radius, give rise to a shorter charge separation between the surface and the adatom, which in turn may determine the change in other properties such as work function and position of the d -band center, as discussed below, commonly linked to the catalytic properties of a given material. , …”

“…In the case of Bi adatoms adsorbed on Pt basal planes, for example, a mixed covalent-metallic nature of Bi–Pt bonding has been calculated, giving rise to a slight polarization of the Bi–Pt bond, despite the similar electronegativity of Bi and Ni atoms, χ P Bi = 1.9. This difference in the bonding character may appear because of the more delocalized nature of valence electrons in Ni due to the partially filled d -orbitals and the smaller Ni atomic radius, r Ni = 124.6 pm, closer to r Pt = 138.5 pm, than r Bi = 154.5 pm, which allows a reduction of ca.…”

Electrocatalysis of Oxygen Reduction on Te-Modified Platinum Stepped Crystal Surfaces

“…The asymmetric oxidation and reduction peaks suggest that the process occurring on Te is irreversible. DFT calculations of the adsorption energy of Te on Pt(100) surfaces indicate that the most favorable adsorption site is the 4-fold hollow site shown in the inset of Figure b . To calculate the Te coverage, we used the adsorption charges on the modified and unmodified electrodes.…”