AbstractResults of potentiodynamic and potentiostatic measurements of the electrooxidation of ammonia traces with platinum as a catalyst in a strong alkaline electrolyte are reported. To improve the performance of a fuel cell, such as an electrochemical gas sensor for ammonia traces, the hydrophobicity of the Teflon‐bonded platinum black gas diffusion working electrode is varied. The expectation that with increasing Teflon content of the catalytic anode the long term characteristics are enhanced could not be confirmed. The weakening of the cell current is influenced much more by effects belonging to the incorporation of carbon dioxide in the electrolyte.—The optimal operating potential for a three‐electrode cell arrangement, which depends also on the cross sensitivities to other gases, is in the range of 1.1 to 1.3 Volts.