Characterization of the SEI by scanning electrochemical microscopy SECM

Scanning Electrochemical Microscopy (SECM) (53) is an electroanalytical technique that has been used to smdy the kinetics of electron transfer in a variety of substrates (54-58). However, there are very few reports about its use in investigating the SEI (23, 59-64). A detailed description of SECM is given in Chapter 12. There are also many review articles that deal extensively with this technique (65-68). 

Conventional techniques have limitations in studies of electron transfer kinetics at an SET In transient techniques such as CV, parallel processes such as electrode corrosion, charging of the double layer, and interference of IR drop contribute significantly to the 

These limitations can be overcome by SECM. One of the important advantages of SECM is that the tip does not need to be a saniconductor. Therefore, any saniconductor electrode can be probed using a Pt UME tip, for example. Since very small currents are measured at the UME tip, the IR drop is minimal. Additionally, the UME tip quickly reaches a steady state due to the small area of the electrode so that effects due to double layer charging are avoided. Because the UME tip is poised at a potential specific to the redox couple used, corrosion processes taking place at semiconductor electrode do not contribute to the tip current. 

Therefore, the flux or mass transport rate (mol s cm ) at the semiconductor substrate is given by 

Reprinted with permission from reference (23). Copyright 1994, American Chemical Society. Mean value. 

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