Electrochemical Oxidation of Fuels in Liquid Ammonia

Overvoltage measurements for the hydrogen and nitrogen evolution reactions in acid ( NH 4 SCN ) liquid ammonia on more than thirty electrode surfaces permit the evaluation of these surfaces as catalysts for the electrochemical oxidation of hydrogen and ammonia in this electrolyte, as well as yielding the electrostability regions available for fundamental electrochemical studies on these surfaces. Testing of various fuels on ten selected electrode surfaces in acid liquid ammonia showed that hydrazine could be oxidized on rhodium and platinum, 1,2‐diphenylhydrazine is oxidizable on mercury, and borohydrides show activity on rhenium and platinum. Constant current oxidation in stirred acid ammonia solutions yields almost 4 electrons per molecule of hydrazine, 2 electrons per molecule of 1,2‐diphenylhydrazine, and 2 to 3 electrons per molecule of potassium borohydride. The activation energies are about 15 kcal/mole for the oxidation of KBH 4 on platinum and 5 kcal/mole for the oxidation of 1, 2‐diphenylhydrazine on mercury. The rate of the oxidation of hydrazine on platinum in acid liquid ammonia solutions does not appear to follow the Arrhenius temperature dependence.