Abstract
The co-adsorption of sulfate, bisulfate and hydrogen on Pt(111) and Au(111) electrodes was studied based on periodic density functional calculations with the aqueous electrolyte represented by both explicit and implicit solvent models. The influence of the electrochemical control parameters such as the electrode potential and pH was taken into account in a grand-canonical approach. Thus, phase diagrams of the stable coadsorption phases as a function of the electrochemical potential and Pourbaix diagrams have been derived which well reproduce experimental findings. We demonstrate that it is necessary to include explicit water molecules in order to determine the stable adsorbate phases as the (bi)sulfate adsorbates rows become significantly stabilized by bridging water molecules.
Highlights
Electrochemistry is concerned with the processes at the interface between an electron conductor, the electrode, and an ion conductor, the electrolyte (Schmickler and Santos, 2010)
Note that in order to be consistent with the further results for the adsorption energies, we have used as a reference for the energies of the adsorbates those given in Equation (13), namely H2 in vacuum and SO2 and H2O embedded in implicit water
A detailed atomistic understanding of the stable anion adsorbate phases as a function of electrochemical control parameters is crucial for, e.g., an assessment of the electrocatalytic activity of a particular electrode/electrolyte interface. In this theoretical and computational study we addressed the structure of Pt(111) and Au(111) in the presence of asulfate containing electrolyte which correspond to benchmark systems in electrochemistry
Summary
Electrochemistry is concerned with the processes at the interface between an electron conductor, the electrode, and an ion conductor, the electrolyte (Schmickler and Santos, 2010). One of the best studied systems is sulfate adsorption on platinum (Shingaya and Ito, 1996; Kolics and Wieckowski, 2001; Herrero et al, 2002; Braunschweig et al, 2010; Garcia-Araez et al, 2010; Santana et al, 2010; ComasVives et al, 2013), but despite various investigations the surface structure of the ad-layer is still controversially discussed The origin of this problem can be traced back to the fact that both sulfate and bisulfate can exist in equilibrium at the electrode/electrolyte interface, but experimentally it is hard to differentiate between these two anions by most electrochemical technics. We discuss the equilibrium of bisulfate and sulfate at the surface of both metals
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