Studies of the methanol crossover and cell performance behaviors of high temperature-direct methanol fuel cells (HT-DMFCs)

The high temperature-direct methanol fuel cell (HT-DMFC) based on phosphoric acid (PA)-doped polybenzimidazole (PBI) membranes shows promise as a passive-type DMFC system because it can operate using highly concentrated methanol fuel. In this paper, the methanol crossover and cell performance behaviors of the HT-DMFCs were investigated using a one-dimensional (1-D) HT-DMFC system model that fully accounts for the electrochemical reactions, key species transport and heat generation inside a cell, and the evaporation processes of liquid methanol/water fuel in the evaporator. The model was first validated against experimental HT-DMFC data measured over a wide range of methanol feed concentrations and operating current densities, and operating characteristics of HT-DMFCs were then explored in detail. Particular emphasis was placed on conducting a comparative study of HT-DMFCs with traditional liquid feed low temperature-DMFCs based on perfluorosulfonic acid membranes. The simulation results showed that a HT-DMFC can operate well under highly concentrated methanol fuel above 12 M due to the minimal degree of methanol crossover through the PA-doped PBI membrane.