Methanol crossover effect for direct methanol fuel cells: Applicability of methanol activity in polymer electrolyte membrane

Abstract

We developed a cell voltage model as a function of the current density response of the direct methanol fuel cell (DMFC). The impact on cell performance by methanol crossover, which lowers the cell performance, is discussed. We employ a srmethanol activity term to take into account the methanol crossover effect. A methanol activity equation is derived from the Helmholtz energy of mixing. In this study, we use a simplified expression of the Helmholtz energy of mixing and correct the mathematical approximation defect using the fractional form. To take the specific interaction into account, a secondary lattice concept, perturbation to a fixed reference system, is introduced. A cell voltage equation with reasonable boundary conditions, including a methanol crossover effect that plays a major role in determining the cell voltage of DMFC, is developed. It can also be found that the methanol crossover increases with an increase in membrane chain length.