Modelling Mobile Species Dynamics within Electroactive Films under Mixed Thermodynamic and Kinetic Control



The mobile species (ion and solvent) content of permselective electroactive films can be represented in 3D compositional space, where the three components are potential (E), charge (Q) and solvent population (ΓS). Having introduced this concept for films undergoing redox switching under thermodynamic control with ideal solvation characteristics, it was previously shown how one could introduce the additional complexity of non-ideal solvation characteristics, or slow charge (electron/ion) transfer kinetics, or slow solvent transfer kinetics. Here, the facility is developed to incorporate any combination of these complexities, providing a more realistic model for “typical” electroactive films. Additionally, the possibility of “asymmetry” in the entry and exit rates of mobile species is considered. A range of specific kinetic and thermodynamic scenarios is explored for a cyclic voltammetric potential control function and represented in (E,Q, ΓS)-space and through solvent:ion flux ratios. These integral and differential compositional representations are directly applicable to experimental data from a wide range of in situ techniques and allow simple visualization and qualitative recognition of specific behavioral types. The responses vary significantly with potential scan rate, underscoring the value of varying experimental timescale in order to highlight specific phenomena and thereby evaluate the relevant thermodynamic or kinetic parameters.