EFFECT OF STRUCTURE ON POROUS GAS-DIFFUSION ELECTRODES FOR PHOSPHORIC-ACID FUEL-CELLS

This investigation is concerned with the variation of structure in the catalyst layer for porous gas-diffusion electrodes. The pore-size distribution and the total pore volume of the electrode are measured by a mercury penetration method. A model that accounts for this incomplete wetting electrode is solved by an orthogonal collocation method and matched with experimental observations. The numerical solution indicates that the effectiveness factor drops noticeably under high current density when the agglomerate radius is greater than 40 mum. When the agglomerate radius is smaller than 1.2 mum, however, the effect of ionic transport becomes important. The maximum reaction rate occurs at carbon-paper/catalyst-layer interface when the effective conductivity of the electrolyte is larger than that of the solid phase. If the effective conductivity of the electrolyte is smaller, then the maximum reaction rate occurs at the electrode/electrolyte interface.