306
Anal. Chem. 1988, 60,306-310
Fast-Scan Cyclic Voltammetry as a Method To Measure Rapid, Heterogeneous Electron-Transfer Kinetics David 0. Wipf, Eric W. Kristensen, Mark R. Deakin, and R. Mark Wightman*
Department of Chemistry, Indiana University, Bloomington, Indiana 47405
The use of fast-scan cyclk votlammetry for the measurement of heterogeneous electron-transfer klnetlcs has been examIned. The dlstortlons caused by the measurement Instrumentation, ohmic drop, and the cell t h e constant have been teed. These parametem comMne to set an upper llmlt on the scan rate at whkh undlstorled data can be achleved. At higher scan rates, meanlngful data can be obtalned and the dlstortlon can be accounted for qualltatlvely. Wlth the exceptlon of the Instrumental dlstortlon, the upper llmlt Is Inversely proporthal to the radius of a dlsk or hemispherical electrode. Several outer-sphere electron-transfer couples have been examined. The measured rate for Ru(NH,)?+ reductlon agrees with literature values. I n contrast, much larger heterogeneous rates are measured for ferrocene oxldatlon and R~(bpy),~+redudlon than have been prevlously reported. The ablllty to obtain electrochemical data at a scan rate of 0.5 Mv s-' Is demonstrated for ferrocene oxldatlon.
The development of disk-shaped ultramicroelectrodes (electrodes of
