Adsorption of bromide at the Ag(100) electrode surface

Abstract

The adsorption and phase formation of bromide on Ag(100) has been studied by chronocoulometry and surface X-ray scattering (SXS). With increasing electrode potential, bromide undergoes a phase transition from a lattice gas to an ordered c(2×2) structure (θ=0.5). The degree of lateral disorder was estimated by comparing the SXS- and the electrochemical measurements. Based on chronocoulometric experiments, a thermodynamic analysis of charge density data was performed to describe the bromide adsorption at the Ag(100) electrode. The Gibbs surfaces excess, electrosorption valencies, Esin–Markov coefficients, and the Gibbs energy of adsorption, lateral interaction energies as well as surface dipole moments have been estimated. The experimental θ versus E- isotherms are modeled employing (i) a quasi-chemical approximation as well as (ii) the results of a recent Monte Carlo simulation. An attempt is made to discuss the structure data and thermodynamic quantities of bromide adsorption on Ag(100) on the basis of the Grahame–Parsons model of the Helmholtz layer.