Supporting data: Modelling the Double Layer of Polycrystalline Electrodes: Capacitance, Potential of Zero Charge, and Parsons–Zobel Plot

This data repository supports the following publication<br>Title: Modelling the Double Layer of Polycrystalline Electrodes: Capacitance, Potential of Zero Charge, and Parsons–Zobel PlotAuthor:Jinwen Liu*, Katharina Doblhoff-Dier*, Marc T. M. Koper** [e-mail], [e-mail], [e-mail]:The double layer capacitance is a central tool to gain insight into the electrical double layer (EDL), yet its interpretation remains challenging. This is true in particular in the presence of surface heterogeneity and specific adsorption. Using a mean-field model, we discuss how these factors shape capacitance curves, affect the potential of zero charge (PZC), and alter the Parsons–Zobel (PZ) plots. The model reveals four distinct regimes of interfacial capacitance behaviour, determined by the facet size and ratio, the Debye length, and differences in PZC and Helmholtz capacitance between facets. These regimes define clear conditions under which capacitance curves exhibit either one or two minima, with the single minimum either coinciding with or deviating from the global PZC. We further demonstrate how adsorption on low-coordinated facets modifies the symmetry and magnitude of capacitance profiles and suppresses PZ slopes. Overall, this work provides a simple yet useful theoretical basis for recognizing and disentangling the respective roles of surface heterogeneity and adsorption in the EDL of polycrystalline electrodes, aiding in the interpretation of experimental results.<br># Description for all files here:<br>- COMSOL_report.docx: report generated by COMSOL. It contains all the inputs, model setup and main results.<br>- Figures_data_Poly_EDL: contain all the data to plot the Figures in the linked paper<br>- plot_poly_EDL_Fig.ipynb: python script to plot the data from "Figures_data_Poly_EDL" and generate the Figures in the main text.<br># How to reproduce the data and the figures in the paper:<br>"COMSOL_report.docx" shows all the equations, input parameters, and example results. By changing the parameters as discussed in the paper, we can calculate the potential (4.4.1 in COMSOL report)and concentration distribution (4.4.1 in COMSOL report), and also the surface free charge as a function of applied potential (4.3.5 Table 18 in COMSOL report). The surface free charge data in various of parameters are shown in the "Figures_data_Poly_EDL.xlsx" and further used to calculate the capacitance curves. All the capacitance curves can be further plot using "plot_poly_EDL_Fig.ipynb" to generate the Figures shown in the paper.