Two-step conditioning method for high power-generating direct methanol fuel cells

Power-generation improvement of a direct methanol fuel cell (DMFC) has been investigated through the enhancements of the anode and cathode characteristics using a newly developed “two-step conditioning method”, in which the conditioning is conducted by supplying H2 gas before the conventional DMFC conditioning. By using the two-step conditioning, the DMFC performances are enhanced. From the polarization curves measured during the DMFC operation using a single cell having an Ag/Ag2SO4 reference electrode, the methanol oxidation performance of the anode is proven to be improved with an increase in the methanol concentration. In addition, a decline in the O2 reduction performance at the cathode due to the methanol crossover is suppressed by our original conditioning method. These results are also supported by the linear sweep voltammetry, and the superior DMFC performances after the two-step conditioning are related to the high speed cleaning of the electrocatalysts. Note that the optimum two-step conditioning leads to 1.4-2.2 times higher maximum power densities than those for the conventional DMFC conditioning even for a shorter conditioning time.