Cavity microelectrode for studying powder materials at a high potential scan rate

Cavity microelectrodes make it possible to study the electrochemical proper ties of powder materials over a large range of potential scan rates. With p olyaniline in 1 M H2SO4 solution, the highest scan rate (S-rat) reaches 400 V/s instead of a few fractions of millivolt per second with the usual comp osite electrode device (CED). This is due to the dramatic decrease of the r eaction volume (approximate to 10(-6) to 10(-7) cm(3)), which corresponds t o 10(-8) to 10(-6) g of material, as compared to a few 10(-1) cm(3) and a f ew milligrams for the usual CED. Screening over an extended S-rat spectrum revealed new electrochemical behaviors, and various characteristics vs. S-r at profiles are established. (C) 1999 The Electrochemical Society. S1099-00 62(99)02-099-4. All rights reserved.