Development of a Self-Adaptive Direct Methanol Fuel Cell Fed with 20 M Methanol

A passive and self-adaptive direct methanol fuel cell (DMFC) directly fed with 20M of methanol is developed for a high energy density of the cell. By using a polypropylene based pervaporation film, methanol is supplied into the DMFC's anode in vapor form. The mass transport of methanol from the cartridge to the anodic catalyst layer can be controlled by varying the open ratio of the anodic bipolar plate and by tuning the hydrophobicity of anodic diffusion layer. An effective back diffusion of water from the cathode to the anode through Nafion film is carried out by using an additive microporous layer in the cathode that consists of 50wt.% Teflon and KB-600 carbon. Accordingly, the water back diffusion not only ensures the water requirement for the methanol oxidation reaction but also reduces water accumulation in the cathode and then avoids serious water flooding, thus improving the adaptability of the passive DMFC. Based on the optimized DMFC structure, a passive DMFC fed with 20M methanol exhibits a peak power density of 42mWcm(-2) at 25 degrees C, and no obvious performance degradation after over 90h continuous operation at a constant current density of 40mAcm(-2).