In situ and real time X-ray diffraction study of an electrocrystallisation process: Ag electrodeposition on Au(111)

Abstract

The electrolytic crystal growth of Ag on Au(111) under a combination of potential step and linear sweep voltammetry has been studied in situ and in real time with X-ray diffraction. The electrodeposition on Ag on Au(111) was an ideal system to study because the two elements have very similar lattice constants (a= 4.09 and 4.08 Å for Ag and Au, respectively) and hence epitaxial growth of Ag layers on Au(111) was expected. In terms of X-ray diffraction studies, the growth of an Ag adlattice on Au(111) led to constructive interference upon X-rays diffracted by the latter. Therefore, the differential diffracted intensity monitored at 2θ= 38.18°, as a function of time during electrodeposition, increased with the growth of the adlattice (electrodeposit). We have demonstrated how the rate of increase of the differential diffraction intensity was affected by the overpotential value stepped to, the potential sweep rate and the measurement time resolution. We conclude that under very well controlled conditions, these measurements could be used as a way of determining the rate and mode of electrolytic crystal growth.