Electrochemical Measurement of the Surface Alloying Kinetics of Underpotentially Deposited Ag on Au(111)

Abstract

The cyclic voltammetry characterizing underpotential deposition (UPD) of Ag onto Au(111) varies in the literature with respect to the characteristic UPD peaks in both position and number. Rooryck et al. (1) confirmed that the discrepancy in terms of peak position, specifically the initial UPD to which a third of a monolayer of deposition is attributed, is due to a variation in the quality of the surface. Clean, smooth Au(111) surfaces yield a peak position of 0.53 V vs Ag0/Ag+, while rough disordered surfaces yield a peak position of 0.61 V vs Ag0/Ag+. Repetitive potential cycling in the UPD region resulted in a gradual shift in peak position, with time as the deposited Ag alloyed with, and was stripped from the surface leaving vacancies. We provide a methodology for tracking the rate at which UPD Ag alloys with the Au(111) surface without the use of continuous potential cycling. A simple kinetic model is developed for the surface alloying of Ag on Au(111), from which we extract an activation barrier and attempt frequency for this process. Notably, we introduce a novel technique for the inexpensive parallel fabrication of Au(111) single crystals that allowed us to build statistics and ensured reproducibility of our data.