Examination of Electrochemical Reactions in 1D Membrane Confinement via Experiments and Numerical Simulations

Anodized aluminum oxide (AAO) membranes are frequently used as template materials for electrodeposition of nanomaterials, due to tunable pore-diameters and interpore distances. However, the fundamental effect of the confined pore environment on electrochemical reactions remains unclear, which limits their usability as vessels for targeted reaction control. We showcase how complex electrochemical systems can be investigated by a combination of experiments and numerical simulations. To this end, the electrochemical reaction of the ferro/ferricyanide redox couple inside of 50 µm thick AAO membranes with pore-diameters of 20 nm is studied. It is demonstrated how simulations can guide the choices of experimental parameters and enable in-depth analysis of experimental data to yield meaningful interpretations on confinement effects and other relevant experimental details. A setup to investigate the effect of confinement on the electrochemistry inside AAO membranes beyond the geometry-induced restricted mass transport is established. Simulations using a lowered diffusion coefficient resulted in a slightly better fit to experimental data of the AAO electrodes than an unmodified system, suggesting that an effect of the confinement might exist. Furthermore, the influence of cell geometry and electrode assembly is demonstrated, while the impact of diffusion rates and pore shapes on the system response is simultaneously analyzed.