Thermodynamics of the formation of surface PtO₂ stripes on Pt(111) in the absence of subsurface oxygen

Abstract

This paper examines the thermodynamics of PtO2 stripes formed as intermediates of Pt(111) surface oxidation as a function of the degree of dilation parallel to the stripes, using density functional theory and atomistic thermodynamics.

In Situ AFM Imaging of Platinum Electrode Surface during Oxidation–Reduction Cycles in Alkaline Electrolyte

“…1.1 V, followed by the formation of an α-PtO 2 phase at 1.25 V . According to density functional theory (DFT) calculations, this initial oxide is rather a suspended oxide than one in which actual place exchange has taken place . After reduction of the oxide, platinum adatoms and vacancies are created on the surface, as well as platinum dissolved in the electrolyte, leading to surface roughening .…”

“…1.1 V, followed by the formation of an α-PtO 2 phase at 1.25 V. 8 According to density functional theory (DFT) calculations, this initial oxide is rather a suspended oxide than one in which actual place exchange has taken place. 9 After reduction of the oxide, platinum adatoms and vacancies are created on the surface, as well as platinum dissolved in the electrolyte, leading to surface roughening. 10 Extensive morphological changes of the platinum surface happen as a result of prolonged oxidation−reduction treatments, as for instance documented in the work by Arvia et al 11,12 The dissolution and surface roughening of polycrystalline platinum in acidic electrolyte due to oxidation and reduction cycles has been studied extensively.…”

Reversible Atomization and Nano-Clustering of Pt as a Strategy for Designing Ultra-Low-Metal-Loading Catalysts

“…The Pt atom can also replace an antisite Mg atom (Pt filling Mg vacancies in the MgAl 3 layer, see Methods) in concert with 2Hs desorbing, yielding Pt 4+ to allow charge compensation, Figure c. The local planar PtO 4 motif resembles the theoretically and experimentally observed PtO 2 ultrathin overlayers on Pt(111) under oxidizing conditions. , The Gibbs free energy change under oxidizing conditions (200 mbar O 2 , 56 mbar H 2 O, and 1025 K) shows that trapping a Pt atom from Pt bulk in an available antisite vacancy coupled with hydrogen removal by O 2 is a downhill reaction by 1.1 eV. This means that Pt has a strong tendency to atomize, especially for low loading, whenever the Mg antisite vacancy concentration exceeds that of Pt.…”

Demystifying the Atomistic Origin of the Electric Field Effect on Methane Oxidation

“…While there is a nice agreement for the negative branch, the slope of the computed positive branch (>1 V) is not as steep as the experimental one. This can be due to the formation of active sites that we did not evaluate such as corners, edges, or simply rough α-PtO 2 islands or other surface oxide arrangements. , Furthermore, even when minimizing the field effects by using a dielectric constant of 1 (Figure S2) the qualitative features do not change, confirming the evolution of the surface state as the origin of the potential dependent activation energy rather than electric field effects.…”