Mathematical modeling of nonlinear reaction-diffusion processes in enzymatic biofuel cells

Enzymatic biofuel cells convert the chemical energy of biofuels into electrical energy by employing oxidoreductase enzymes as catalysts. They have attracted considerable attention due to their potential use as a promising alternative to traditional power sources. Also, enzyme-modified electrodes have important applications in electrochemical biosensors, bioreactors, implantable medical devices as well as in biochemistry as a source of information on the action of enzymes. Among the different electrochemical techniques available, enzymatic biofuel cells and electrodes are generally studied via cyclic voltammetry, chronoamperometry, polarization curves and impedance measurements to gain better insight into the enzymatic system. The main aim is to assess the influence of the mediator species and its diffusivity, the loading of biocatalysts, the amount of substrates, mediators and inhibitors, the strategy of enzyme immobilization, etc. as well as to study the enzymatic kinetic mechanism. Within this context, mathematical models must be used to understand, predict and optimize the performance of enzymatic biofuel cells and electrodes as a function of the chief experimental parameters above mentioned. In this review article, major recent research activity concerning the mathematical modeling of enzymatic electrodes and fuel cells is discussed, highlighting the main contributions as well as current problems and challenges.