SCANNING ELECTROCHEMICAL MICROSCOPY OF A POROUS MEMBRANE

Measurement of the local flux of electroactive ions across a porous membrane using scanning electrochemical microscopy (SECM) is described. SECM consists of rastering a hemispherical microelectrode (approximately 3.0-mu-m diameter), held at constant electrochemical potential, across the membrane surface and oxidizing (or reducing) electrochemically active species that emerge from membrane pores. The resulting faradaic current is plotted to construct images of ion pathways in the membrane. SECM images resulting from the passive and electrophoretic flux of potassium ferrocyanide through 1.3-mu-m radius pores in mica are reported.