An analytical overpotential model of a direct liquid-feed fuel cell

Direct liquid-feed fuel cells are considered potential devices that provide power for portable electronic applications. Fuel crossover is one of the key issues in a low-temperature fuel cell like DMFCs. It confines the fuel cell performance and makes mass transfer mechanisms and electrochemical reactions more complex. It is thus essential to investigate the mass transfer behavior and the concentration distribution of the reactants and products before analyzing such a fuel cell. In this paper, an analytical overpotential model of a direct methanol fuel cell (DMFC) is introduced based on our pre-established fuel crossover model, which provides fuel crossover fluxes and fuel concentration profiles. By acquiring polarization data of a DMFC, parameters in the model are fitted meanwhile a variety of overpotentials are recognized. The degradation effects on the individual overpotentials are also evaluated. The resultant model is represented as explicit functions of significant operating variables: temperature, fuel concentration, and current density. The proposed approach can serve as the basis of system control strategies and adopted for fuel cell characterization to enhance fuel cell efficiency.