PREPARATION AND CHARACTERIZATION OF MATRICES FOR PHOSPHORIC-ACID FUEL-CELLS

In this work results on the preparation, characterization and single c ell testing of matrices for phosphoric acid fuel cells are reported. T he matrices were produced using mixtures of powders of silicon carbide with zirconium silicate or niobium carbide, by deposition of an aqueo us emulsion of the powders on top of the catalyst layer of the gas dif fusion electrodes, or by making a self-supported him of the materials. The physical characterization of the powders and of the matrices incl uded the distribution of particle size and shape of the powders and th e thickness, electrical resistance, and pore size distribution in the matrices. The matrices were evaluated under operation, using standard supported platinum on carbon gas diffusion electrodes in a H-2/O-2 Sin gle fuel cell setup operating with phosphoric acid at 180 degrees C. T he results of the cell potential-current density characteristics were analysed to separate the contribution of the structural properties of the matrices on the total polarization losses of the single cells. It was found that a single cell operating with a self-supported matrix co mposed of 50 wt% NbC + SiC has a much better performance than that obs erved with SiC alone.