Alkaline Direct Methanol Fuel Cell---Effect of Operating Conditions on Cell Performance

Searching for alternative power and energy sources has gained much attention due to the high cost and dwindling crude petroleum oil supply. Among the alternative sources, fuel cells are a popular topic because of environmentally friendly advantages. Among several types of fuel cells, proton exchange membrane fuel cells (PEMFC) and direct methanol fuel cells (DMFC) use proton conducting polymer membranes. The DMFC has many advantages over the PEMFC, including higher energy density, simpler system, long life-time, low poisonous emission, and possibility of ambient temperature start-up. The proton exchange membrane based on perfluorosulfonic acid (PFSA) polymer, Nafion for example, is widely used for PEMFC applications. Nafion has high proton conductivity, good thermal, chemical, and mechanical properties. However, the high methanol (MeOH) permeability through Nafion from anode to cathode is too high to use in DMFC devices. This MeOH cross-over causes MeOH poisoning at the cathode and low efficiency of fuel consumption due to reactant (MeOH) losses. Therefore, research aimed at the development of new electrolyte membranes with suppressed MeOH permeability are actively underway. The objective of this proposal is to develop poly(vinyl alcohol) (PVA) nanocomposite membranes with hydroxide conductive capacity for alkaline DMFC applications. PVA will be modified with nano-particle addition, polyelectrolyte blending, nanoclay or nano-metal incorporation. The physical, chemical, electrical properties of the resulting membranes will be characterized. The sorption, diffusion and permeation of MeOH, water and hydroxide ion through the membranes will be determined. The resulting films will be assembled into a single cell and tested for performance. The modification methods can be applied to other membranes to suppress MeOH crossover while maintaining sufficient conductivity.

Project ID:PB9709-3568
External Project ID:NSC97-2221-E182-029