Cl electrosorption on Ag(1 0 0): Lateral interactions and electrosorption valency from comparison of Monte Carlo simulations with chronocoulometry experiments

Abstract

We present Monte Carlo Simulations using an equilibrium latticegas model for the electrosorption of Cl on Ag(100) single-crystal surfaces. Fitting the simulated isotherms to chronocoulometry experiments, we extract parameters such as the electrosorption valency γ and the next-nearest-neighbor lateral interaction energy φ nnn . Both coverage-dependent and coverage independent γ were previously studied, assuming a constant φ nnn [I. Abou Hamad, Th. Wandlowski, G. Brown, P.A. Rikvold, J. Electroanal. Chem. 554-555 (2003) 211]. Here, a self-consistent, entirely electrostatic picture of the lateral interactions with a coverage-dependent φ nnn is developed, and a relationship between φ nnn and γ is investigated for Cl on Ag(100).

Reply to “Remarks on the simulation of Cl electrosorption on Ag(1 0 0) reported in Electrochimica Acta 50 (2005) 5518”

“…2.2 of our Ref. [4] (and also quoted verbatim in the fifth paragraph of LH [1]), is that we take g = 0. This leads to Lorentz' approximation γ PZC = −λ [6] and corresponds to the situation that the full potential drop happens between the bulk metal and the IHL.…”

“…This is indeed the condition corresponding to the experiments reported in Refs. [4,5]. The electrode potential is then E = φ met + cst., where φ met is the potential of the metal.…”

“…Details of our arguments, including the approximations used in Ref. [4] (and also in Ref. [5]), are given below.…”

“…In their interesting discussion article [1], Láng and Horányi (LH) question the concept of electrosorption valency [2,3] as interpreted in our recent paper on Cl electrosorption on Ag(100) [4]. As we understand their argument, its central point is the requirement of charge neutrality in the solution phase and separately in a surface layer consisting of the specifically adsorbed ions (traditionally known as the Inner Helmholtz Layer, IHL) and the adjoining part of the metal in the working electrode.…”

“…[4] correspond to the approximations of excess supporting electrolyte, as well as to identifying the electrosorption valency with the negative of the partial charge-transfer coefficient. While not exact, these are reasonable approximations, supported a posteriori by the good agreement between the numerical results for our model system and the experimental adsorption isotherms.…”