Mathematical modeling of overpotentials of direct glucose alkaline fuel cell and experimental validation

Development of a mathematical model for batch-type direct glucose fuel cell (DGFC) and validation of the model with experimental results in terms of i-V characteristics is attempted. The DGFC model equation is derived to predict the cell voltage at a given current density considering overall ohmic overpotential and activation and concentration overpotentials at anode. The activation overpotential is modeled by taking into account the reaction mechanism of glucose electro-oxidation available in literature and a semi-empirical equation is used to estimate the concentration overpotential. The charge transfer coefficient used in estimation of activation overpotential for different anode catalysts, namely, PtAu/C, PtPdAu/C, and PtBi/C, is determined from cyclic voltammetry analyses. The ohmic resistance is calculated from specific conductance of KOH solution found from non-linear regression analysis given in literature. Two different parameters, m and k are used in estimation of concentration overpotentials. While k signifies departure from ideal i-V characteristics and its value used is 1, m is area-specific resistance for mass transport and its value is 0.2 ka"broken vertical bar cm(2) for PtAu/C and PtPdAu/C and 0.12 ka"broken vertical bar cm(2) for PtBi/C. The trend of current-voltage characteristics at different operating conditions, such as anode catalysts, anode loadings, glucose, and KOH concentrations, is predicted reasonably by the proposed model.