Simultaneous scanning electrochemical and photoelectrochemical microscopy by use of a metallized optical fiber

A technique for combining scanning electrochemical microscopy (SECM) and scanning photoelectrochemical microscopy (PEM) is described, The experimental setup is described and the several modes of operation are discussed. The electrochemical characteristics of the probe, collection efficiency current efficiency, and the coupling efficiency for the two techniques, are examined in several model systems. SPECM was used to identify pitting precursor (PPS) sites on a titanium sample with a 50 Angstrom oxide layer in an acidic KBr solution. It was found that the PPS site could be imaged photoelectrochemically and that the photocurrent is reduced at the PPS.