A mean-field model for the double layer of stepped platinum single-crystal electrodes

Mean-field models are useful in quantitative interpretation of electrochemical measurements and identification of key parameters and processes for further first-principles computations. Herein, we present a mean-field model for the double layer of stepped Pt[n(111) x (110)] single-crystal electrodes. This model accounts for chemisorption-induced surface dipoles from multiple adsorbates (H-ad and OHad) at multiple adsorption sites (terrace and step sites). It is demonstrated that lateral interactions depend on both the adsorbate and the substrate and structure-dependent chemisorption brings about non-trivial effects to the surface-charging behavior and double layer capacitance. Moreover, we emphasize the importance of the activity of interfacial water molecules in understanding the pH and cation effect of voltammetric peaks.