Determination of Heterogeneous Electron Transfer Rate Constants at Microfabricated Iridium Electrodes

Rosemary Feeney and Samuel P. Kounaves*
Department of Chemistry, Tufts University, Medford, MA 02155 U.S.A.

*Author to whom correspondence should be addressed (skounave[at]tufts.edu).

There has been an increasing use of both solid metal and microfabricated iridium electrodes as substrates for various types of electroanalysis.  However, investigations to determine heterogeneous electron transfer rate constants on iridium, especially at an electron beam evaporated or dc magnetron sputtered surface, have not previously been performed.  This paper compares the results of these microfabricated surfaces using ultramicroelectrode arrays and steady-state currents.  Even though the dc magnetron sputtered iridium surface demonstrated a slightly more reversible electrochemical behavior than the electron beam evaporated surface, overall the microfabricated microelectrodes and ring electrode indicated similar reversibility as the polished metallic iridium disk electrode.