Abstract Electrodes with low hydrogen overpotential such as platinum or skeleton nickel are very suitable catalysts for the anodic oxidation of hydrazine. On the other hand, there are electrodes with remarkably high hydrogen overpotential, such as amalgamated sintered nickel, on which hydrazine can be oxidised in the vicinity of the thermodynamic hydrogen potential. In contrast to the reaction on platinum, the hydrazine molecule undergoes no dehydrogenation at the amalgamated sinter nickel electrode, but the hydrogen is directly discharged without being previously split off the hydrazine molecule. The reason for this different behaviour is evidently the small heat of adsorption of hydrogen on mercury: On electrodes with high hydrogen overpotential such as amalgamated sinter nickel the heat of adsorption of hydrogen atom is not sufficiently large to split the hydrazine molecule. On electrocatalysts with low hydrogen overpotential, such as platinum or nickel, the splitting of the (N 2H 3H)-bond and, therefore, the dehydrogenation of the hydrazine molecule is energetically preferred.