ELECTROLYTE ADDITIVES FOR PHOSPHORIC-ACID FUEL-CELLS

Electrochemical characteristics of a series of modified phosphoric aci d electrolytes containing fluorinated car on compounds and silicone fl uids as additives are presented. When used in phosphoric acid fuel cel ls, the modified electrolytes improve the performance due to the enhan ced oxygen reduction rate. Among useful additives we found potassium p erfluorohexanesulfonate (C6F13SO3K), potassium nonafluorobutanesulfona te (C4F9SO3K), perfluorotributylamine [(C4F9)3N], and polymethylsiloxa nes [(-Si(CH3)2O-)n]. The wettability of the electrodes by the modifie d electrolytes also is discussed, as a fuel-cell performance with the modified electrolytes. Specific conductivity measurements of some of t he modified phosphoric acid electrolytes are reported. At a given temp erature, the conductivity of the C4F9SO3K-modified electrolyte decreas es with an increasing amount of the additive; the conductivity of the remains at the same value as the conductivity of the pure phosphoric a cid. At a given composition, the conductivity of any modified electrol yte increases with temperature. We conclude that the improved cell per formance for modified electrolytes is not due to any increase in condu ctivity.