Mass transport and modulation effects in rocking dual-semi-disc electrode voltammetry

• Voltammetric methodology based on rocking disc is introduced.
• With single-disc experiments uniform mass transport and hydrodynamic current enhancements are observed.
• A predictive equation for the mass transport controlled limiting current is proposed.
• For dual-semi-disc electrode modulation effects are demonstrated in generator–collector mode.

A hydrodynamic electrochemical method based on a rocking disc system with 90° amplitude and a frequency range of 0.83–16.7 Hz is reported. The system is versatile and similar in characteristics to the familiar rotating disc voltammetry method (e.g. providing a uniform diffusion layer but without sliding contacts), except for the more complex flow pattern imposed by the oscillatory movement. A Levich-type mass transport limited current response linear with the square root of rocking frequency is obtained. Additionally, a dual-semi-disc generator–collector system is demonstrated and characterised for the one-electron quasi-reversible Fe(CN)63−/4− redox couple. Generator–collector current efficiencies vary from 3% to 6% and characteristic transient concentration modulation effects are observed suitable for Fourier transform analysis. Rotational asymmetry in the flow pattern is detected.