Modelling pH and Potential in Dynamic Structures of the Water/Pt(111) Interface on the Atomic Scale

Martin Hangaard Hansen, Anders Nilsson, and Jan Rossmeisl

Submitted to PCCP, 2017

Abstract

We present atomic-scale structures of the Pt(111)/water interface, by calculating distributions of atomic distances as functions of pH. The structure of the Pt(111)/water interface is a particularly interesting model system in electro-catalysis for proton exchange reactions, especially the oxygen reduction reaction in polymer electrolyte membrane fuel cells. Further insight into such reactions requires accurate simulations of the electrolyte structure in the interface. The study displays many interesting details in the behaviour of the electrolyte structure, e.g. that the electrolyte structure average responds to the presence of protons by a H-down water orientation and that hexagonal adsorbed water layers are present only when they are anchored at the surface by HO*. New adsorbate configurations were also found at 5/12 ML coverage of HO*, suggesting an explanation for reported cyclic voltammetry experiments. The present study is a step towards a more complete understanding of the structure of the electrochemical interface on the atomic scale.

Key-value pairs: Description
Efermi: float. The fermi energy calculated by GPAW
Ekin: float. Total kinetic energy from molecular dynamics (AIMD)
Had: integer. Initial number of adsorbed hydrogen atoms in the trajectory.
Initial: string. Name of the initial structure
OH: integer. Initial number of adsorbed HO* in the trajectory.
Protons: integer. Initial number of solvated protons in the trajectory.
Restart: integer.
Series: Name of calculation series.
Step: integer. Time step.
Temperature: float. Thermostat target temperature.
wfbot: float. Work function calculated on the bottom (metal) side of the system in z direction.
wftop: float. Work function calculated on the top (water) side of the system in z direction.

Querying the Database

The ASE database is of the SQLite3 type. It has around 110000 rows and it is therefore quite slow to query directly. It is faster to simply loop through the full database and use some if statements to select a subset as in the example below.

Download database

Download example