Electrochemistry Fundamentals
Potential of zero charge, chemisorption...
SEED has the unique ability in quantitatively discern changes in the electrical double layer due to active (i.e., reaction at the electrode) and passive (i.e., charging at the electrode) electrochemical processes. Two orthogonal measurements can be performed to distinguish the adsorbed ions from the charge state of the EDL. The EDL is typically 2-5 nanometer thick. Below are examples to demonstrate this capability:
The potential of zero charge (PZC) is an important property of an electrode, for example, to store charge for application in supercapacitors. PZC is the difference in Fermi level (or electrochemical potential) between the electrode and the electrolyte. Unfortunately, direct measurement of PZC is difficult. SEED has the unique capability to directly map local PZC. For the first time, complete passivation of an electrode with a monolayer of graphene is shown by pointing the laser on spots away from the edge of graphene.
SEED can measure the nature of chemisorption process during an electrochemical reaction. In a typical electrochemical reaction such as for Ruthenium Hexamine ion that tends to adsorb on gold because of amine groups, a pronounced minimum is observed at the oxidation and reduction potentials (Mode 1). Mode 2 on the same spot, without moving the sample, the "turnover" of the oxidation/reduction process is measured as a peak. The peak quantifies the local electrochemical redox current.