Scanning Electrochemical Microscopy in the AC-Mode
Abstract
Local electrochemistry is widely used for sensing the heterogeneous reactivity of an interface giving rise to the development of
different techniques during these last decades. For example, the electrochemical microcell, which consists in a glass pipette
capillary1,2 or a scanning droplet cell,3 has been mainly used for corrosion studies for probing a small surface area, the size of
which is controlled by the capillary or the droplet dimension. This technique has been recently revisited by Unwin et al. for
improving both its spatial resolution and the positioning of the capillary, thus allowing the activity at grain and grain boundary to
be visualized at the submicrometer scale.4,5 The scanning vibrating electrode technique (SVET)6,7 was first developed for monitoring
ionic current in the vicinity of individual living cells by measuring the local potential difference at the two extremum
positions of a vibrating probe. It was then widely used for corrosion studies such as galvanic coupling between two metals or pitting
corrosion, thus allowing anodic and cathodic zones to be distinguished. The local electrochemical impedance spectroscopy
(LEIS)8–10 also requires the local current density to be probed in solution, but it takes advantage of a frequency-resolved measurement over the usual frequency range of electrochemical impedance spectroscopy and has been used mostly in corrosion
and corrosion protection, especially for coating degradation monitoring.