| Over the past 15 years, the electrical performance of direct methanol fuel cells (DMFCs) has increased at least tenfold. While the DMFC has a theoretical energy density of 6094 W h/kg, only 1000-3200 W h/kg of this energy is realized in practice. Although most portable power applications only necessitate several W h/kg, performance and cost issues associated with polymer electrolyte membranes (PEMs), anode and cathode catalysts, system design, and operational considerations must be overcome for DMFCs to have a role in the methanol economy.; Water management within a direct methanol fuel cell is critical to achieve optimal performance, especially at higher current densities where increased water production occurs. The semi-interpenetrating network composite membrane, poly(styrenesulfonic acid) poly(vinylidene fluoride) is shown to have dramatically decreased water flux due to electroosmotic drag compared to the conventional material, NafionRTM--117. In addition, a potentiometric method for screening new proton exchange membrane candidates is illustrated as a rapid method for determination of methanol crossover.; Electrooxidation of other small hydrocarbon fuels, such as formic acid, methyl formate, ethylene glycol, and dimethyl oxalate were investigated in a direct oxidation fuel cell (DOFC). At room temperature, formic acid outperforms methanol by virtue of reduction in fuel crossover. Alternative catalyst systems for these fuels must be further investigated. Gold has a tolerance for methanol while promoting reduction of oxidation, and has proved to be a promising candidate as a cathode catalyst. |
