Application of scanning electrochemical microscopy to generation/collection experiments with high collection efficiency

The technique of scanning electrochemical microscopy (SECM) was introduced by Bard and co-workers (1) who have utilized it in a variety of experiments (2). The use of a microelectrode placed close to a substrate electrode to detect electroactive products generated at the latter, as described by Engstrom and co-workers (3,4),is one attractive application of the SECM technique (1). In previous studies, this type of generation/detection experiment has usually been carried out with the microelectrode used as the detector electrode (1-5). In the present study, a larger (100 µm diameter) substrate electrode is used to detect and collect electrode reaction products generated at a microtip electrode positioned at various distances above the substrate electrode. The collection efficiency (in the sense employed for rotating ring-disk electrodes (6)) of such an arrangement is virtually 100% at easily achievable separation distances. The advantages of carrying out generation/collection experiments with the present apparatus are exemplified with some simple experimental systems. Comparisons with similar recent experiments in which arrays of microband electrodes are utilized (7,8) are also provided.