METHODS FOR CHARACTERIZING STRUCTURE AND ELECTROCHEMICAL BEHAVIOR OF TEFLON-BONDED PT ELECTRODES

The Teflon-bonded electrode represents a very efficient structure which allows extensive utilization of the catalyst and therefore very high current densities at relatively low polarization. This electrode has been extensively used in fully engineered fuel cells and in many catalyst screening programs. From this work, the following conclusions can be reached-- Under normal fuel cell conditions, all the Pt surface of Teflonbonded electrodes in good electronic contact with the current collection grid is found to be in good ionic contact with the bulk of thelectrolyte, indicating that the model of the flooded agglomerate is correct-- The IR drop between the front and back of the electrode, even at 100 ma/sq cm, is neglible for an electrode with 30% TeflonThe microporosity of Teflon-bonded electrodes is about 80 to 90% while the macroporosity varies from 50 to 72%-- Under the condition used in this work, the performance (current density at a pracitcal potential of 400 mv vs RHE) of a Pt-Teflon electrode as a propane anode in 85% H//3PO//4 and at 150 C is almost independent of Teflon content in the range 20 to 40%, although the peak current increases with increasing Teflon content. The performance decreases sharply for Teflon content of 15 and 50%.