Modeling Polycrystalline Electrode-electrolyte Interfaces: The Differential Capacitance. Issue 10 (24th June 2020)

• Record Type: Journal Article
• Authors: Müller, Rüdiger; Fuhrmann, Jürgen; Landstorfer, Manuel
• Is Part Of: Journal of the Electrochemical Society. Volume 167:Issue 10(2020)
• Publication Date: 2020-06-24
• Subjects: double layer -- polycrystal -- differential capacitance -- finite-element -- stochastic representation; Electrochemistry -- Periodicals; 541.3705
• DOI: 10.1149/1945-7111/ab9cca
• Languages: English
• ISSNs: 0013-4651

Abstract

Abstract : We present and analyze a model for polycrystalline electrode surfaces based on an improved continuum model that takes finite ion size and solvation into account. The numerical simulation of finite size facet patterns allows to study two limiting cases: While for facet size diameter d facet → 0 we get the typical capacitance of a spatially homogeneous but possible amorphous or liquid surface, in the limit 1 [ nm ] ≪ d facet, an ensemble of non-interacting single crystal surfaces is approached. Already for moderate size of the facet diameters, the capacitance is remarkably well approximated by the classical approach of adding the single crystal capacities of the contributing facets weighted by their respective surface fraction. As a consequence, the potential of zero charge is not necessarily attained at a local minimum of capacitance, but might be located at a local capacitance maximum instead. Moreover, the results show that surface roughness can be accurately taken into account by multiplication of the ideally flat polycrystalline surface capacitance with a single factor. In particular, we find that the influence of the actual geometry of the facet pattern in negligible and our theory opens the way to a stochastic description of complex real polycrystal surfaces.