Determination of heterogeneous electron transfer kinetics in the presence of ultrasound at microelectrodes employing sampled voltammetry

The technique of sampled voltammetry at microelectrodes irradiated with ultrasound is demonstrated for the first time, This technique is used to determine the heterogeneous electron transfer rate constants for the redox couples ferrocene/ferrocenium, Ru(NH3)(6)(3+)/(2+), and IrCl63-/IrCl6(2-). Determination of the heterogeneous rate constants is also achieved for comparison purposes by analysis of fast sweep rate voltammetry of the redox systems studied at microelectrodes and comparison of the results obtained to the theory developed by Nicholson and Shain. The heterogeneous rate constants determined using sampled voltammetry were 1.0, 0.6, 1.23, and 0.18 cm s(-1) for the ferrocene/ferrocenium (0.1 mol dm(-3) TEATFB, CH3CN), Ru(NH3)(6)(3+/2+) (0.1 mol dm(-3) KCl), IrCl63- (1 mol dm(-3) KCl), and IrCl63-/IrCl62- (1 mol dm(-3) NaCl), respectively, in agreement with those obtained in the absence of ultrasound.