Mass Transport at Microband Electrodes: Transient, Quasi-Steady-State, and Convective Regimes

Mass transport at microband electrodes is investigated theoretically and experimentally in unstirred solutions by chronoamperometry and cyclic voltammetry. Because natural convection limits the convection-free domain up to which diffusion layers may only expand, several regimes of mass transport are identified through simulation by means of a previous model. A zone diagram is established which allows all relative contributions to mass transport to be delineated according to the electrode dimension, timescale of experiment, and amplitude of natural convection. In opposition to the quasi-steady-state regime usually expected at microband electrodes under diffusion control, a steady-state regime always occurs at long enough times. By comparison to microdisk electrodes, a greater influence of natural convection is predicted. These results are validated experimentally by monitoring current responses and mapping steady-state concentration profiles at microband electrodes.