Survey on direct methanol fuel cells with imidazolium-based ionic liquids as the fuel solvent

Abstract

Conventional DMFCs are facing some challenges such as the volatility of water and the fragility of the thin polymer film. To address these challenges, nonvolatile room temperature ionic liquids can be used as the fuel solvent and electrolyte in a fuel cell. In this paper, a series of 1,3-dialkylimidazolium tetrafluoroborate ionic liquid analogues were characterized as the fuel solvent in a DMFC model. Compared to the fuel cell with water as a solvent, the results indicated that some imidazolium-based ionic liquids could be successfully used as the fuel solvent although the performance was still not comparable to aqueous fuel solutions. Among the tested ionic liquids, [C10MIm][BF4] with a larger cation was apparently inferior to other analogues in terms of open circuit voltage, internal resistant and maximum power. [C4MIm][BF4] and [C8MIm][BF4] were the best. When [C4MIm][BF4] was used as the fuel solvent, the fuel concentration could be very high, making it possible to design high energy density fuel cells with such ionic liquids.