Sonoelectrochemistry in Highly Resistive Media: Mass Transport Effects

Sonovoltammetry methodology is studied for the enhancement of electrochemical processes in highly resistive media. As model systems the reduction of [FeCp*₂]PF₆ (with Cp℧ = η⁵-C₅Me₅) and the oxidation of FeCp*₂ in acetonitrile are examined at a 25 μm diameter Pt microdisk electrode. Both in the presence and in the absence of supporting electrolyte ultrasound induces a strong increase in the observed limiting current in agreement with an increase in mass transport or, associated with this, a change in the average diffusion layer thickness. However, iR drop effects cause distortion of voltammetric waves, potential fluctuation, and ultrasonically induced current decrease under conditions of extremely low ionic strength.