Modelling of Reaction and Diffusion Processes in a High‐surface‐area Biofuel Cell Electrode Made of Redox Polymer‐grafted Carbon

Abstract

AbstractA mathematical model considering reaction and diffusion processes in biofuel cells, such as enzyme reactions, apparent electron diffusion in the redox polymer, and diffusion of a substrate in a redox polymer film, verified the effectiveness of a high‐surface‐area biofuel cell electrode with a thin, grafted redox polymer layer. The model calculation shows that the rate‐limiting step of apparent electron diffusion can be overcome by using the electrode with a thin redox polymer, even when the redox polymer used has a low apparent electron diffusion coefficient. In the electrode, increase in the second‐order rate constant for the reaction between an enzyme and a mediator above a certain value does not increase the current density, and thus the mediator used in the electrode should have an adequate second‐order rate constant and a more negative redox potential. In addition, increase in the turnover rate of the enzyme and the surface coverage of the enzyme allows an increase in the current density; the surface coverage of the enzyme has the most influence. Based on these calculations, it is important to realise high‐surface‐area electrodes with a thin redox polymer, and with high enzyme loading.