Anion Exchange Membrane-Modified Electrodes for Alkaline Fuel Cells

The direct methanol alkaline fuel cell (DMAFC) is under development as an alternative power source for lightweight, portable applications. Several advantages of the alkaline fuel cell make it superior to direct methanol PEM fuel cells. Namely, the improved electrokinetics of fuel oxidation in alkaline environments make it possible to use a variety of fuels and inexpensive, non-noble catalysts while minimizing fuel crossover and cathode flooding issues often encountered with PEM fuel cells. These inherent advantages of alkaline fuel cells are somewhat offset by issues with electrode/electrolyte poisoning by precipitated carbonates in alkaline solutions. Using solid polymer electrolytes can mitigate this problem, but commercial anion exchange membranes generally exhibit decreased conductivity and stability compared to their PEM counterparts and the lack of a commercially available soluble ionomer for electrode construction results in electrode/electrolyte interfaces with increased ionic resistivities leading to power loss. The proposed DMAFC will improve the membrane/electrode interface using a novel electropolymerization step and increase the conductivity by in situ quaternization/crosslinking of an anion conducting polymer directly to the electrolytically modified electrode. These improvements, coupled with judicious selection of electrocatalysts, will lead to the construction of a 5 W cell stack with excellent power density and power-to-weight ratio.