CORROSION BEHAVIOR OF A PHOSPHORIC-ACID FUEL-CELL UNDER AIR LEAKAGE USING A SINGLE CELL WITH MULTIREFERENCE ELECTRODES

Air leak from the air side to the fuel side through a matrix defect (pinhole) was simulated in a single cell with multi-reference electrodes (RHEs), and changes of the anode, cathode and RHEs potentials in the horizontal plane of a PAFC were studied. Along the fuel flow channel downstream of the simulated matrix defect, the cathode potential exceeded 1.5 V vs.RHE, and cathode carbon corrosion was observed in that area. In this area, protons are consumed by leaked air, and local acidity change of the electrolyte causes a potential shift, then cathode carbon corrosion occurs due to the high (nobler) cathode potential in that area. The changes of the potential shift always coincided with the changes of the RHE potentials. Disagreement between electrochemical potential and electric potential, which comes from the resistance of ions in the plane of a matrix, is the origin of the significant potential shift.