The design and construction of high-performance direct methanol fuel cells. 2. Vapour-feed systems

The construction of a gas-fuel-feed direct methanol fuel cell is described in detail and the optimisation of the active electrode fabrication process is also reviewed. For this vapour phase-system, it has proved possible to develop a Nation encapsulated process in which the porous carbon electrodes were bonded with Nafion rather than polytetrafluoroethylene (PTFE). Initially, PTFE was removed only from the anode paste, but it was found that PTFE was also unnecessary at the cathode. The best performance was found for extremely thin catalysed carbon layers at the two electrodes, and to reduce loadings, thin layers of uncatalysed carbon were inserted between the carbon cloth current collectors and the catalysed carbon layers. The final electrodes had loadings of 2 mg cm −2 on the anode and 0.5 mg cm −2 on the cathode and gave peak power densities of 0.35 W cm −2 with oxygen and 0.22 W cm −2 with air as the combustant.