Electrochemical AFM (EC-AFM)
Electrochemical AFM mode enables measurements while electrochemical reactions are taking place in electrolyte solutions on an electrode surface. Electrochemical reactions are processes in which electrons flow between solid electrodes and substances in solution, involving a reduction reaction (at the cathode) and an oxidation reaction (at the anode). These reactions are widely studied in applications such as corrosion and photovoltaics. EC-AFM measurements enable monitoring of the electrode structure during such reactions and establishing the relationship between the electrode structure/morphology and its electrochemical activity.
Because these studies typically occur in aggressive liquid environments, excellent environmental control and protection of AFM electronics is necessary for effective imaging. The Nanosurf Flex-Axiom series, combined with the electrochemistry stage ECS204, is ideally suited for these measurements, as all the AFM electronics are protected and positioned above the liquid, and the cantilever holders are made of a special corrosion-resistant material.
Shown below is a study of nucleation and growth of copper clusters under electrochemical control. Cyclic voltammograms were used to charactize the electrochemical reactions and establish suitable potentials to observe topographical changes under stable electrochemical conditions.
Nucleation was observed by AFM at E = -50mV in sulphoric acid vs a platinum quasi reference electrode. Increasing the potential E = -10mV reduced the growth rate and a single copper cluster could be followed by time-lapse AFM. This reaction is reversible and at positive potentials the cluster was dissolved again.
The height of the ECS204 electrochemical stage is constructed so that it can also accommodate standard, rod-like electrodes. In the example below, dissolution of deposited copper clusters on a polished rod-like platinum electrode at oxidizing conditions was observed by AFM.
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