Transient Analysis of a Passive Direct Methanol Fuel Cell Using Pure Methanol

A two-dimensional, transient, nonisothermal, multifluid, and multicomponent model is developed to evaluate the transient operation of a completely passive direct methanol fuel cell utilizing pure methanol at the fuel cartridge. The model simultaneously considers the mass, species, heat, charge, and dissolved water transport using a single computational domain. A hydrophobic, microporous layer is used at the cathode to facilitate sufficient water recovery from the cathode to the anode. Methanol crossover is directly interconnected to water crossover in such a way that if there is enough back flow of water from the cathode to the anode, methanol solution is sufficiently diluted at the anode catalyst layer and, consequently, methanol crossover is reduced. Although the electro-osmotic force drags substantial amount of water from the anode to the cathode, convective and diffusive mechanisms are employed to force the water back to the anode. A cell using initially water-saturated porous layers at the anode can successfully operate employing pure methanol if a proper water supply from the cathode is provided. It is also revealed that a successful operation of a completely passive cell has a strong dependence on the cell geometry as well as cell operating voltage. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3491449] All rights reserved.