Computational Investigation of Polar Surface/Electrolyte Interfaces

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Polar surfaces of solids are surfaces with a net effective charge density. Polar surfaces can be created by terminating an ionic solid by a plane with a net charge. Also surfaces of ferroelectric compounds are polar when the surface is not parallel to the bulk polarization. Gas phase polar surfaces are unstable against non-stoichiometric reconstruction or depolarization in case of ferroelectric compounds. A first objective of the project is to verify whether polar surfaces can be stabilized by ions in an electrolyte screening the surface charge (electric double layer formation). The second aim is to investigate the surface chemistry of such polar surface-electrolyte interfaces by computing chemisorption energies, surface acidities and redox potentials of electro-active species. These (free) energies will be compared to the corresponding energies of non-polar surfaces of the same compound.The computational method to be used is Density Functional Theory based Molecular Dynamics (DFTMD) extended with a recently developed finite field technique for the treatment of electric double layers in periodic model systems (arXiv preprint arXiv:1609.07754 (2016)). This study is a first step in a computational exploration of the potential of polar surfaces in heterogeneous catalysis. Model systems that will be considered are main group oxides, such as Al2O3, d0 transition metal oxides such as ZrO2 and ferroelectric solids such as PbTiO3 used in heterogeneous acid base chemistry.