Mathematical modelling of an enzymatic fuel cell with an air-breathing cathode

Multi-dimensional steady-state and dynamic models for an enzymatic fuel cell are developed. In the model system, the biocatalyst (glucose oxidase) is immobilized in a porous electrically conducting anode, while glucose and a mediator are supplied from a solution. A platinum air-breathing cathode and a Nafion membrane complete the cell unit. Detailed mass and charge balances are combined with a model for the ping-pong reaction mechanism in the anode, together with oxygen reduction in the cathode. The effects of enzyme oxidation by dissolved oxygen in the anode (a competing side reaction) are also included. The model is validated against experimental polarization and power curves, and the steady-state performance under different conditions is analyzed and discussed. The simulation results demonstrate some of the possible limitations of enzymatic fuel cells and provide insights into the spatial distributions of the reactants, potentials and current.