A non-electroneutral model for complex reaction-diffusion systems incorporating species interactions

In this study we develop a general framework for describing reaction-diffusion processes in a multi-component electrolyte in which multiple reactions of different types may occur. Our motivation for this is the need to understand how the interactions between species and processes occurring in a complex electrochemical system. We use the framework to develop a modified Poisson-Nernst-Planck model which accounts for the excluded volume interaction (EVI) and incorporates both electrochemical and chemical reactions. Using this model, we investigate how the EVI influences the reactions and how the reactions influence each other in the contexts of the equilibrium state of a system and of a simple electrochemical device under load. Complex behaviour quickly emerges even in relatively simple systems, and deviations from the predictions of ideal solution theory, together with how they may influence the behaviour of more complex system, are discussed.