The Effect of Ammonia on Hydrogen‐Air Phosphoric Acid Fuel Cell Performance

Abstract

Laboratory experiments and tests conducted on phosphoric acid fuel cells have indicated that ammonia, when present as an impurity in either the fuel or oxidant streams, will react with the electrolyte to form . Ammoniation of the acid to greater than 0.2 mole percent resulted in a loss in performance due primarily to a lowering in the rate of reduction on the the cathode catalyst. Complete recovery of the performance loss was achieved after the removal of the contaminant source. The degree of electrolyte conversion and, hence, steady‐state performance loss were found to be dependent on the rate of ammonia addition to the cell relative to the rate of ammonium ion oxidation at the cathode. This oxidation process was found to be potential dependent, with an increase in cathode potential resulting in the ability of the cell to tolerate higher concentrations in the reactant gas streams.